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Egbebiyi, Temitope Samuel, Olivier Crespo, Christopher Lennard, Modathir Zaroug, Grigory Nikulin, Ian Harris, Jeff Price, Nicole Forstenhäusler, and Rachel Warren. "Investigating the potential impact of 1.5, 2 and 3 °C global warming levels on crop suitability and planting season over West Africa." PeerJ 8 (May 5, 2020): e8851. http://dx.doi.org/10.7717/peerj.8851.
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West African rainfed agriculture is highly vulnerable to climate variability and change. Global warming is projected to result in higher regional warming and have a strong impact on agriculture. This study specifically examines the impact of global warming levels (GWLs) of 1.5°, 2° and 3 °C relative to 1971–2000 on crop suitability over West Africa. We used 10 Coupled Model Intercomparison Project Phase5 Global Climate Models (CMIP5 GCMs) downscaled by Coordinated Regional Downscaling Experiment (CORDEX) Rossby Centre’s regional Atmospheric model version 4, RCA4, to drive Ecocrop, a crop suitability model, for pearl millet, cassava, groundnut, cowpea, maize and plantain. The results show Ecocrop simulated crop suitability spatial representation with higher suitability, observed to the south of latitude 14°N and lower suitability to its north for 1971–2000 for all crops except for plantain (12°N). The model also simulates the best three planting months within the growing season from September-August over the past climate. Projected changes in crop suitability under the three GWLs 1.5–3.0 °C suggest a spatial suitability expansion for legume and cereal crops, notably in the central southern Sahel zone; root and tuber and plantain in the central Guinea-Savanna zone. In contrast, projected decreases in the crop suitability index value are predicted to the south of 14°N for cereals, root and tuber crops; nevertheless, the areas remain suitable for the crops. A delay of between 1-3 months is projected over the region during the planting month under the three GWLs for legumes, pearl millet and plantain. A two month delay in planting is projected in the south, notably over the Guinea and central Savanna zone with earlier planting of about three months in the Savanna-Sahel zones. The effect of GWL2.0 and GWL3.0 warming in comparison to GWL1.5 °C are more dramatic on cereals and root and tuber crops, especially cassava. All the projected changes in simulated crop suitability in response to climatic variables are statistically significant at 99% confidence level. There is also an increasing trend in the projected crop suitability change across the three warming except for cowpea. This study has implications for improving the resilience of crop production to climate changes, and more broadly, to food security in West Africa.
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Dessalegn, Obssi. "Propagation Methods of Yam (Dioscorea Species) with Special Attention to In Vitro Propagation." Journal of Applied Biotechnology 4, no. 1 (February 15, 2016): 13. http://dx.doi.org/10.5296/jab.v4i1.9031.
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<p>Yam is a monocotyledonous plant in the genus Dioscorea. It is a multi-species tuber crop cultivated in Africa, Asia and parts of South America. Yam is an important crop in South and Southwestern parts of Ethiopia. Many species of Dioscorea genus are economically important crops and many of them have been used in the pharmaceutical industry. Yam is propagated from seed tubers or sections of tuber and corms. Seed tubers are expensive, bulky to transport and the multiplication rate in the field is very low. Shortage of seed tubers for planting is one of the major constraints for yam production in Ethiopia. To overcome such problems and to increase production, different propagation methods have been implemented for many Dioscorea species. Convectional and In vitro propagation of Dioscorea species pave the way to meet the demand of this economically important plant. The protocols are designed to provide the optimal levels of mineral nutrients, environmental factors, vitamins and carbohydrates to achieve the high regeneration rate of the different species of Dioscorea in vitro. This review summarizes some of the important reports on different propagation technique of Dioscorea from the literature data.</p>
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Mansvelt, E. L., and E. Carstens. "Outbreak of Erwinia carotovora on Zantedischia spp. in South Africa." Plant Disease 83, no. 10 (October 1999): 966. http://dx.doi.org/10.1094/pdis.1999.83.10.966c.
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In South Africa, summer-flowering Arum lilies are grown for the tuber, potted plant, and cut flower markets. In 1998, an outbreak of soft rot was detected on Zantedischia oculata cv. Black Magic and Z. elliottiana plants from several nurseries. Crop losses of up to 25% were incurred. The initial symptom was wilting of leaves. When plants were lifted from the soil, soft rot of the tuber was found. Tuber rot usually developed on one side, and plants developing from affected tubers wilted and died. No discoloration of leaf or tuber tissues was found. Isolations from diseased tissues consistently yielded bacterial colonies that were translucent, white, and glistening and that had entire margins on nutrient agar. Ten representative isolates were chosen for further characterization. Erwinia carotovora subsp. carotovora strain B56 was included as a reference strain. All isolates were gram-negative rods, oxidase and arginine dihydrolase negative, catalase positive, and facultatively anaerobic. They degraded pectate and rotted potato slices but did not hydrolyze starch. All isolates fermented glucose, reduced nitrates to nitrites, and grew at a maximum temperature of 37°C. Isolates produced acids from D(+)-glucose, D(+)-cellobiose, melibiose, amygdalin, L(+)-arabinose, D-mannitol, L(+)-rhamnose, sucrose, ribose, D(-)xylose, and D(-)glucose but not from D-arabinose, D-sorbitol, or maltose. Isolates liquefied gelatin and used citrate, arbutine, esculin, salicin, and cellobiose as the sole carbon source. Pathogenicity to Zantedischia spp. was tested by injection of tubers with an inoculum suspension containing 108 CFU/ml. Control plants were inoculated with sterile distilled water. Inoculated plants were kept in a greenhouse at 24°C. Symptoms developed 2 days after inoculation with the pathogen and appeared to be identical to those observed on diseased material in nurseries. Control plants did not rot. The bacterium was readily reisolated from diseased plants, confirmed to be the inoculated pathogen, and identified as E. carotovora, based on morphological, biochemical, and physiological characteristics and pathogenicity. E. aroideae has been reported to cause soft rot of rhizomes of winter-flowering Arum lilies (Z. aethiopica) in South Africa (1). However, this is the first report of soft rot caused by E. carotovora subsp. carotovora on tubers of Z. oculata and Z. elliottiana plants in South Africa. Reference: (1) V. Wager. 1970. Flower Garden Diseases and Pests. Purnell, Cape Town, South Africa.
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Matthiessen, J. N., and S. E. Learmonth. "Impact of the soil insects African black beetle, Heteronychus arator (Coleoptera: Scarabaeidae) and Whitefringed weevil, Graphognathus leucoloma (Coleoptera: Curculionidae), on potatoes and effects of soil insecticide treatments in south-western Australia." Bulletin of Entomological Research 85, no. 1 (March 1995): 101–11. http://dx.doi.org/10.1017/s0007485300052068.
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AbstractPopulations of the soil insects African black beetle, Heteronychus arator (Fabricius), and whitefringed weevil, Graphognathus leucoloma (Boheman), and the damage caused to potato crops in south-western Australia were measured with and without the insecticide chlorpyrifos incorporated into the soil prior to planting. Low populations of both insects were highly damaging. Destruction of stems by H. arator reduced tuber yield and both species damaged tubers from the time of their formation. Tuber damage increased with time because both insect species on average damaged multiple tubers and caused multiple attacks on tubers. Growth of G. leucoloma larvae caused increased abundance of the more damaging later instars in spring. The insecticide reduced resident H. arator abundance and hence damage to newly-emerging potato stems in summer, but had less effect on reducing attacks on tubers in summer crops because adult beetles flew into some crops during growth. Exceptionally high tuber damage per H. arator adult in winter crops was ascribed to enhanced activity during its spring breeding season. The insecticide was inconsistent in reducing the abundance of G. leucoloma larvae. Insecticidal effects were greatest near the soil surface, resulting in an increase in the relative proportion of both insects deeper in the soil. Since a greater proportion of the tubers occurred there, the resulting greater potential for the insects to cause tuber damage tended to outweigh reduction in their abundance.
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Witbooi, Hildegard, L. Kambizi, and O. Oguntibeju. "An alternative health crop for South Africa: Purple potato mini tuber production as affected by water and nutrient stress." African Journal of Food, Agriculture, Nutrition and Development 20, no. 06 (October 31, 2020): 16818–31. http://dx.doi.org/10.18697/ajfand.94.19850.
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Food security in South Africa ranks as one of the top ten priorities in the country. Potato is a fundamental staple food crop in South Africa, providing essential nutrition. While there are several cultivars currently in production for the potato market, there is a need to explore cultivars that are available, but not utilised within the country. Pigmented potatoes are not regarded as high value on the South African market;however,yield prospects as well as health-promoting benefits could have a positive contribution on the South African Gross Domestic Product (GDP) and on the population’s health. Potato cultivar (cv.) Salad blue(SB)seems to be a drought-tolerant crop with the ability to produce reasonable yields under severe environmental conditions. In order to promote cv. SB as a possible food security option for South Africa, there is a critical need for empirical information, describing some basic horticultural as well as biochemical information and vitamin C presence. This study investigated the potential of pigmented potato SB tubers as an alternative to high yielding white potato for the South African market.Tubers of Solanum tuberosum cv. BP1 and SB, were used for this research.The high amounts in phenolic compounds in SB can be considered to be health-promoting phytochemicals. Anticarcinogenic, antibacterial, antiviral properties have been reported. A greenhouse, bag trial with virus-free plantlets of BP1 and SB cultivars was conducted using three water and nutrient levels and favourable root zone temperature(100% without heat, 100% heated, 50% heated, 25% heated) all grown in coco peat. Cultivar SB showed nearly two-fold yield compared to the control BP1. Methanol extracts of the tubers were assessed for their total polyphenolic, flavanol, and flavonol contents as well as 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability, ferric reducing antioxidant power (FRAP), Trolox equivalence antioxidant capacity (TEAC),anthocyanin and L-ascorbic acid assays.The aqueous extract of the SB tubers was found to contain higher level of total polyphenols (320 mg GAE/g), and flavonol (85 mg QE/g) than the extract of the BP1 tubers with values of173 mg GAE/g (total polyphenol), and67 mg QE/g (flavonol). Similarly, the methanol extract of the tuber skins also exhibited higher DPPH (818,86 IC50mg/mL), FRAP (18,19μmol AAE/g), and TEAC (911,12μmol TE/g)than the extract of the BP1with DPPH (595,99 IC50mg/mL), FRAP (10,86 μmol AAE/g) and TEAC (435,44 μmol TE/g). The present study provides useful information for farmers and health professionals in respect to increased yield and health-promoting benefits of an underutilized potato variety.
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Muzhinji, Norman, and Jacquie E. van der Waals. "Population Biology and Genetic Variation ofSpongospora subterraneaf. sp.subterranea, the Causal Pathogen of Powdery Scab and Root Galls on Potatoes in South Africa." Phytopathology® 109, no. 11 (November 2019): 1957–65. http://dx.doi.org/10.1094/phyto-12-18-0467-r.
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Spongospora subterranea f. sp. subterranea, causal agent of powdery scab and root galls of potatoes, occurs worldwide and is responsible for quality and yield losses in potato production in South Africa. Despite being one of the most important potato pathogens in South Africa, little information is available on the genetic structure and diversity of S. subterranea f. sp. subterranea, which could provide insight into the factors shaping its evolution and the role of inoculum sources in disease development. A total of 172 samples were collected from four potato growing regions in South Africa. An additional 27 samples obtained from Colombia were included for comparative purposes. The samples were screened against six informative microsatellite (simple-sequence repeat) markers. Of the 172 samples obtained from potato growing regions in South Africa, there were 75 multilocus genotypes (MLGs), only 16 of which were shared between potato growing regions, indicating substantial gene flow and countrywide dispersal of the pathogen. The presence of common MLGs among the root- and tuber-derived samples indicated a lack of specialization of S. subterranea f. sp. subterranea to either tuber or root infection. Nei’s unbiased estimates of gene diversity for the clone-corrected data were low and ranged from 0.24 to 0.38. Analysis of molecular variance and discriminant analysis of principal components showed no population differentiation between different potato growing regions in South Africa and between root- and tuber-derived genotypes. The presence of MLGs, high considerable genotypic diversity, and failure to reject the null hypothesis of random mating in most populations are indicative of some kind of recombination, either sexual or asexual, in these S. subterranea f. sp. subterranea populations. Information from this study provides new insights into the genetic structure and diversity of S. subterranea f. sp. subterranea in South Africa. Continuous monitoring of the pathogen population dynamics will be helpful in implementing effective region-specific management strategies for the pathogen, especially in the development of resistant potato cultivars.
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Gouws, R., and A. McLeod. "Fissure Scab, a New Symptom Associated with Potato Common Scab Caused by a Streptomyces sp. in South Africa." Plant Disease 96, no. 8 (August 2012): 1223. http://dx.doi.org/10.1094/pdis-12-11-1056-pdn.
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Common scab caused by Streptomyces spp. is one of the major factors limiting successful potato (Solanum tuberosum) production in South Africa. Most potato cultivars are susceptible to the disease and huge losses are incurred due to a reduction in cosmetic value. Common scab symptoms that have been reported worldwide are variable, with circular, raised, tan-to-brown, corky lesions being the most common symptoms. However, a distinct atypical symptom was observed in isolated production regions (Western Free State and Mpumalanga) in South Africa since early 2010. Deep longitudinal fissures (3 to 12 mm) containing scab-like lesions were observed on the surface area of tubers from several potato cultivars (Mondial, BP1, and Buffelspoort). Lesions on Mondial were interesting since this cultivar, but not the susceptible BP1 and Buffelspoort cultivars, is tolerant to typical common scab in South Africa. Isolations were made from tuber lesions obtained from the two production regions and were plated onto yeast malt extract medium. Several pure culture strains were obtained that were positively identified as Streptomyces spp. based on morphology. Species identity of four strains was investigated using PCR primers targeting the 16S rRNA region of known species (3), which showed that the strains did not belong to any of the known pathogenic reference strains (S. scabiei, S. europascabiei, S. turgidiscabies, S. acidiscabies). Species identity of the strains was further investigated through sequencing of the 16S rRNA region (1.2 kb). The four strains had 100% sequence similarity (GenBank Accession. No. JQ241439) to each other and to 15 GenBank sequences that included several unknown Streptomyces spp., S. vinaceus, S. malachiticus, S. werraensis, S. cyaneus (the only published sequenced), and S. pseudogriseolus. The sequence of the isolates had only 95.5% identity to the most prevalent common scab pathogen, S. scabiei (GI154707840, [3]). The pathogenicity of the four strains, along with an S. scabiei reference isolate, was investigated using BP1 potato tubers and the double pot methodology (1). Fifteen-centimeter pots containing silica sand were each planted with one potato tuber and placed on top of a rectangular planting box (15 × 1.5 × 0.4 m) filled with native Hutton soil. The 15-cm pots were irrigated until the roots grew into the Hutton soil. Subsequently, irrigation was only applied to the Hutton soil, thus creating dry conditions in the tuber development area (15-cm pot), which is conducive for common scab development. The potato plants were inoculated with 10- to 14-day-old Streptomyces strains during the tuber initiation stage at a concentration of 1 × 106 spores/ml of sterile water, 10 ml per plant, and six replicates per strain. Ten weeks after inoculation, each of the four strains caused cracking and scabbing, similar to initial symptoms observed, on more than 90% of the tubers. The S. scabiei reference isolate caused typical circular, raised, brown, corky common scab lesions. Streptomyces was reisolated from the lesions, fulfilling Koch's postulates. To our knowledge, these results indicate that a previously unreported Streptomyces sp. is the causal agent of a new lesion type, fissure scab, on potato in South Africa that may lead to serious losses to the local potato industry. References: (1) L. Marais and R. Vorster. Potato Res. 31:401, 1988. (2) D. J. Theron. Page 1 in: Guide to Potato Production in South Africa, 2003. (3) L. Wanner. Phytopathology 96:1363, 2006.
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Muzhinji, N., J. W. Woodhall, M. Truter, and J. E. van der Waals. "Elephant Hide and Growth Cracking on Potato Tubers Caused by Rhizoctonia solani AG3-PT in South Africa." Plant Disease 98, no. 4 (April 2014): 570. http://dx.doi.org/10.1094/pdis-08-13-0815-pdn.
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Rhizoctonia solani consists of 13 anastomosis groups (AGs) designated AG1 to 13. AG3-PT is considered the predominant AG in potatoes (4) and is associated with quantitative and qualitative yield losses. Qualitative losses are typically associated with the tuber blemish disease, black scurf. However, atypical tuber blemishes such as elephant hide consisting of corky lesions on the tuber surface (2) have also been attributed to Rhizoctonia. Such atypical blemishes are not considered specific to Rhizoctonia, making direct-cause effect estimates difficult (1). Koch's postulates for the elephant hide symptom and R. solani AG3-PT have not been completed. Recently, growth cracking and scab lesions were observed on potato tubers in South Africa and attributed to a new Streptomyces species (3). These lesions and cracks were similar to elephant hide symptoms attributed to R. solani AG3-PT. Therefore, the cause of the elephant hide symptom in South Africa was investigated further. Symptoms of elephant hide and cracking have been observed on tubers from the Eastern Free State, KwaZulu-Natal, Limpopo, Mpumalanga, North-Eastern Cape, Northern Cape, North West, Sandveld, and Western Free State growing regions. In 2012, three samples of potato tubers (cv. BP1) with elephant hide and cracking were selected for analysis. These samples were collected from Clanwilliam in the Sandveld potato growing region. Tubers were surface sterilized with 1% NaOCl; sections of affected tissue were excised and plated onto potato dextrose agar (PDA). Rhizoctonia-like colonies were identified and after further sub-culturing on PDA, three representative isolates (Rh3, Rh4, and Rh6) of R. solani from each sample were obtained. For each isolate, genomic DNA was extracted and the rDNA ITS region sequenced using ITS1-F and ITS4 (2). The resulting sequences (KF234142, KF234143, and KF234144) were at least 98% identical to other AG3-PT sequences on GenBank (JX27814 and KC157664). To confirm Koch's postulates, pathogenicity tests were conducted with the three isolates. PDA plugs of each isolate were added to 10 g of barley grains which were incubated for 14 days until fully colonized. The barley grains were then used to inoculate disease-free mini-tubers (cv. BP1) in 5l pots containing a sand-clay-pine bark mixture (1:1:1 ratio). Potato plants inoculated with sterile barley grains served as controls. Plants were held for 120 days in a greenhouse at 22°C with light for 12 h a day. Incidence of the elephant hide symptom for isolates Rh3, Rh4, and Rh6 was 58%, 33%, and 37.5%, respectively. Growth cracking and black scurf were also observed with each isolate. R. solani AG3-PT was successfully re-isolated from symptomatic tubers, confirming Koch's postulates. This is the first report of R. solani AG3-PT causing elephant hide in potato tubers in South Africa. Elephant hide caused by R. solani AG3-PT has been reported in tubers from France (2) and the United Kingdom (3), but Koch's postulates were not proven. In this study, Koch's postulates were proven for R. solani AG3-PT causing scab or elephant hide symptom and cracking in potato tubers. R. solani AG3-PT should thus be considered in addition to Streptomyces as a cause of this symptom and control strategies should also consider R. solani AG3-PT. References: (1) G. J. Banville et al. Pages 321-330 in: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control, B. Sneh et al., eds. Kluwer Academic Publishers, Dordrecht, The Netherlands, 1996. (2) M. Fiers et al. Eur. J. Plant. Pathol. 128:353, 2010. (3) R. Gouws and A. McLeod. Plant Dis. 96:1223, 2012. (4) J. W. Woodhall et al. Eur. J. Plant. Pathol. 136:273, 2013.
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Zarka, Kelly A., Ria Greyling, Inge Gazendam, Dean Olefse, Kimberly Felcher, Gurling Bothma, Johan Brink, Hector Quemada, and David S. Douches. "Insertion and Characterization of the cry1Ia1 Gene in the Potato Cultivar Spunta for Resistance to Potato Tuber Moth." Journal of the American Society for Horticultural Science 135, no. 4 (July 2010): 317–24. http://dx.doi.org/10.21273/jashs.135.4.317.
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Potato tuber moth (Phthorimaea operculella) is a serious pest of potatoes in tropical and subtropical regions of the world, including South Africa. The cry1Ia1 gene (from Bacillus thuringiensis) under the control of the 35S cauliflower mosaic virus promoter was transformed into the potato (Solanum tuberosum) cultivar Spunta to develop a cultivar with resistance to potato tuber moth for release in South Africa. Two transformation events, ‘SpuntaG2’ and ‘SpuntaG3’, were selected and subjected to extensive molecular analyses as required by the regulatory agencies of South Africa. Southern hybridization experiments indicated that ‘SpuntaG2’ and ‘SpuntaG3’ had one and three copies of the cry1Ia1 gene, respectively, and that the gene insertion was stable through multiple clonal generations. Furthermore, the sequence of the cry1Ia1 gene in ‘SpuntaG2’ was compared with the known sequence of the cry1Ia1 gene and found to be identical. Polymerase chain reaction (PCR) amplification using primers for plasmid “backbone” genes demonstrated that ‘SpuntaG2’ contained no backbone plasmid genes, whereas ‘SpuntaG3’ contained several backbone plasmid genes. Therefore, further analyses were limited to ‘SpuntaG2’, and event-specific primers were developed for this cultivar. Analysis of the left and right border regions in ‘SpuntaG2’ demonstrated that the insertion of the cry1Ia1 gene did not disrupt any functional genes nor did it create new open reading frames that encoded proteins with a significant match to the non-redundant sequence database queried by the BLASTP program. Enzyme-linked immunoabsorbent assays (ELISA) tests indicate that the cry1Ia1 gene was expressed at a mean concentration of 2.24 μg·g−1 fresh weight in leaf tissue and 0.12 μg·g−1 fresh weight in tubers. This study demonstrates the extensive molecular characterization that is necessary to apply for deregulation of a genetically modified crop and these data have been used in a regulatory package for the general release of ‘SpuntaG2’.
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Muzhinji, N., J. W. Woodhall, M. Truter, and J. E. van der Waals. "First Report of Rhizoctonia solani AG 4HG-III Causing Potato Stem Canker in South Africa." Plant Disease 98, no. 6 (June 2014): 853. http://dx.doi.org/10.1094/pdis-11-13-1131-pdn.
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Black scurf and stem canker caused by Rhizoctonia solani Kühn (teleomorph: Thanathephorus cucumeris Frank Donk) are potato diseases of worldwide economic importance (4). R. solani consists of 13 anastomosis groups (AGs) of which AG 3-PT is considered the dominant causal agent of potato diseases globally (1,4). However, other AGs such as AG 2-1, 5, and 8 have been reported to cause potato diseases (1,4). In February 2013, potato stem samples (cv. Mondial) displaying dark brown lesions resembling those caused by Rhizoctonia stem canker were obtained from a commercial field in Limpopo Province, South Africa. Symptomatic tissue was disinfected with 1% NaOCl for 1 min, rinsed in sterile water, and 4-mm stem pieces excised from the margins of symptomatic tissues and plated on 2% water agar supplemented with 20 mg/l of chloramphenicol. Single hyphal tips taken from fungal isolates identified as R. solani based on morphological traits (3) were transferred to potato dextrose agar. DNA was isolated from the resulting cultures and ITS region of rDNA was sequenced as previously described (2). The resulting sequences of three of the isolates, Rh 81, Rh 82, and Rh 83 (KF712285, KF712286, and KF712287), were 99% similar to those of AG 4 HG-III found in GenBank (DQ102449 and AF354077). Therefore, based on molecular methods, these three isolates were identified as R. solani AG4 HG-III. To determine pathogenicity of the AG4 HG-III isolates, certified disease free mini-tubers (Generation 0, cv. Mondial, produced in tunnels) were used in pot trials. PDA plugs of each isolate were added to 10 g of barley grains, which had been sterilized by autoclaving for two consecutive days at 121°C for 30 min, and were incubated for 14 days until fully colonized. Ten colonized barley grains were placed 10 mm above each mini-tuber planted in 5l pots containing sterile potting mixture of sand:clay:pinebark (1:1:1). Ten tubers were inoculated with each isolate. Uninoculated, sterile barley grains were applied to the control treatment. Mini-tubers were grown in a greenhouse maintained at 22°C with light for a 12 h day. After 7 weeks, five plants for each isolate were destructively sampled and assessed for stem canker symptoms. At 120 days after sowing, the remaining five plants per treatment were assessed for blemishes on progeny tubers. The stem canker incidences of plants inoculated with Rh 81, Rh 82, and Rh 83 were 25, 25, and 50%, respectively, whereas no symptoms were observed in control plants. Sclerotia formation and blemishes were not observed on any of the progeny tubers, which might indicate that these strains are only able to infect stems, or that environmental conditions were not suitable for tuber blemish or black scurf development. R. solani AG4 HG-III was consistently re-isolated from symptomatic stems displaying brown lesions, and the identity of the re-isolates were confirmed by molecular tests as previously described, thereby fulfilling Koch's postulates. To our knowledge, this is the first report of R. solani AG4 HG-III causing stem canker on potato in South Africa and worldwide. Knowledge of which AGs are present in crop production systems is important when considering disease management strategies such as crop rotation and fungicide treatments (3). References: (1) C. Campion et al. Eur. J. Plant. Pathol. 109:983, 2003. (2) N. Muzhinji et al. Plant Dis. 98:570, 2014. (3) L. Tsror. J. Phytopathol. 158:649, 2010. (4) J. W. Woodhall et al. Plant. Pathol. 56:286, 2007.
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Marquez-Villavicencio, Maria del Pilar, Russell L. Groves, and Amy O. Charkowski. "Soft Rot Disease Severity Is Affected by Potato Physiology and Pectobacterium taxa." Plant Disease 95, no. 3 (March 2011): 232–41. http://dx.doi.org/10.1094/pdis-07-10-0526.
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Pectobacterium species cause disease worldwide in many crop and ornamental plants, including potato. A new Pectobacterium subspecies, P. carotovorum subsp. brasiliensis was recently described in Brazil and later found in the United States, Israel, and South Africa. Its virulence traits and host range remain unknown. A comparison of three taxa commonly found on potato showed that both P. carotovorum subsp. carotovorum and subsp. brasiliensis are more aggressive in causing tuber and stem soft rot than P. atrosepticum. Also, despite bacterial growth inhibition in vitro of P. carotovorum subsp. carotovorum and P. atrosepticum strains by P. carotovorum subsp. brasiliensis, this new subspecies and P. carotovorum subsp. carotovorum are able to co-colonize in the same infected tissue. Both subspecies were motile in lesions. Pathogenesis assays showed that host ranges of all three overlap, but are not identical. The host ranges of individual strains of P. carotovorum subsp. carotovorum and subsp. brasiliensis are limited, whereas P. atrosepticum can macerate many plant species in addition to potato. There was high variability in virulence assays with potato tuber; thus physiological factors were investigated. Tuber size, maturity, and field location had significant effects on susceptibility to soft rot, with larger, more mature tubers being more susceptible.
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Muzhinji, Norman, James W. Woodhall, Mariette Truter, and Jacquie E. van der Waals. "Relative Contribution of Seed Tuber- and Soilborne Inoculum to Potato Disease Development and Changes in the Population Genetic Structure of Rhizoctonia solani AG 3-PT under Field Conditions in South Africa." Plant Disease 102, no. 1 (January 2018): 60–66. http://dx.doi.org/10.1094/pdis-03-17-0329-re.
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Understanding the contribution of seed tuber- and soilborne inocula of Rhizoctonia solani AG 3-PT in causing potato disease epidemics is an important step in implementing effective management strategies for the pathogen. A 2-year study was conducted to evaluate the contribution of each source of inoculum using an integrative experimental approach combining field trials and molecular techniques. Two distinct sets of genetically marked isolates were used as seed tuberborne and soilborne inocula in a mark-release-recapture experiment. Disease assessments were done during tuber initiation and at tuber harvest. Both inoculum sources were found to be equally important in causing black scurf disease, whereas soilborne inocula appeared to be more important for root and stolon infection, and seedborne inocula contributed more to stem canker. However, seed tuber-transmitted genotypes accounted for 60% of the total recovered isolates when genotyped using three polymerase chain reaction restriction fragment length polymorphism markers. The changes in population structure of the experimental R. solani population over the course of the growing season and across two growing seasons were investigated using eight microsatellite markers. The populations at different sampling times were somewhat genetically differentiated, as indicated by Nei’s gene diversity (0.24 to 0.27) and the fixation index (FST). The proportion of isolates with genotypes that differed from the inoculants ranged from 13 to 16% in 2013 and 2014, respectively, suggesting the possibility of emergence of new genotypes in the field. Because both soilborne and tuberborne inocula are critical, it is important to ensure the use of pathogen-free seed tubers to eliminate seed tuberborne inoculum and the introduction of new genotypes of R. solani for sustainable potato production in South Africa.
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Laurie, S. M., P. N. Myeza, M. J. Mulabisana, K. G. Mabasa, A. Thompson, R. Greyling, M. Cloete, and P. O. Adebola. "In vitro propagation and disease testing as a means of producing healthy planting materials to support root and tuber crops production in South Africa." Acta Horticulturae, no. 1113 (March 2016): 225–32. http://dx.doi.org/10.17660/actahortic.2016.1113.34.
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Malan, A. P., R. Knoetze, and H. J. Hugo. "First Report of the Root-Knot Nematode Meloidogyne javanica on Buchu (Agathosma betulina) in South Africa." Plant Disease 88, no. 5 (May 2004): 574. http://dx.doi.org/10.1094/pdis.2004.88.5.574a.
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Agathosma betulina, commonly known as buchu, has been used for centuries by the indigenous people of South Africa for medicinal purposes. Currently, the essential oils from buchu are used in medicine, food flavorings, and aromatic oils. Increased exploitation of natural growing buchu in the Fynbos biome and a worldwide shortage of buchu oil encouraged commercial cultivation in South Africa. The root-knot nematode (Meloidogyne spp.) is one of the most common plant-parasitic nematodes found on commercial crops grown in the Western Cape. It has also been isolated from the soil and roots of plants in the natural Fynbos vegetation (2). In June 2003, a nursery propagating buchu plants experienced problems with poor growth. Examination of the buchu roots under a stereo microscope showed extensive galling with large numbers of female root-knot nematodes with eggsacs. Nematode extractions of the soil were also done. Only second-stage juveniles of Meloidogyne spp. (311 per 250 ml of soil) were recovered. A polymerase chain reaction (PCR)-based diagnostic method (1) was used for the identification of the root-knot nematode species. Ten intact females were dissected from the roots and individually placed directly in 5 μl drops of 1× PCR reaction buffer (16 mM [NH4]2SO4, 67 mM tris-HCL, pH 8.8, 0.1% vol/vol Tween 20) ontaining 60 μg/ml of proteinase K. The tube was kept at -80°C for a minimum of 10 min. The tube was incubated at 60°C for 15 min and 5 min at 95°C. The PCR amplifications were then prepared directly in the same tube. Amplified DNA fragments were digested with HinfI and DraI. The digested DNA was loaded on a 2% agarose gel, separated by electrophoresis, and detected by ethidium bromide staining. The digested amplified DNA fragments correspond to those of Meloidogyne javanica. Morphological characteristics were used to verify the PCR-based identification of the nematode. To our knowledge, this is the first report of M. javanica causing extensive galling on the roots of Agathosma betulina. Visual damage to the roots indicates the root-knot nematode to be an important threat to the commercial cultivation of buchu. References: (1) R. Knoetze. Potential of the polymerase chain reaction for the identification of plant-parasitic nematodes. M.Sc. thesis. University of Stellenbosch, Stellenbosch, South Africa, 1999. (2) A. J. Meyer, S. Afr. J. Enol. Vitic., 20:75, 1999.
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OLASANTAN, F. O., A. W. SALAU, and E. E. ONUH. "INFLUENCE OF CASSAVA (MANIHOT ESCULENTA) INTERCROP ON GROWTH AND FRUIT YIELDS OF PEPPER (CAPSICUM SPP.) IN SOUTH-WESTERN NIGERIA." Experimental Agriculture 43, no. 1 (January 2007): 79–95. http://dx.doi.org/10.1017/s0014479706004200.
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In tropical Africa, pepper (Capsicum spp.) is grown as a rainfed crop, and its production is limited by the long, hot growing season. Field experiments were conducted in Nigeria to evaluate the effects of cassava (Manihot esculenta) on the growth and yields of three pepper cultivars and gross returns in 2001–2003. In Experiment 1, pepper (cv. Sombo) was planted between rows of cassava cvs Idileru (PI), Odongbo (PO) and TMS 30572 (PT). In Experiment 2, pepper cvs Sombo, Tatase and Atarodo, were mixed with TMS 30572 (MS, MT or MA). The growth environment for the intercropped pepper differed from sole crops of pepper. Radiant energy reaching the soil surface, maximum diurnal soil and canopy temperatures, and weed growth were lower with intercropping, with the lowest values being observed in the PI and PT intercrops. Similarly, soil moisture content and the number of earthworm casts were greater with intercropping, with the highest values also occurring in the PI and PT intercrops. In both experiments, fresh fruit yields of pepper depended on the duration of harvest, the number of fruits per plant and the weight of fruits. In Experiment 1, although the number of fruits and fruit yield of cv. Sombo were greater in the sole crop (SP) than the PO intercrop, the fruit yields in the PI and PT intercrops were similar to those of the SP plot. In Experiment 2, the number of fruits and yield of intercropped pepper cvs Tatase, Sombo and Atarodo were 25–28 % higher, on average, than in pure stands. Cassava tuber yield was not affected by intercropped pepper in either experiment. Total gross returns were greater than growing either pepper or cassava in monoculture. Increased total gross returns in the intercrops were obtained in the PI and PT treatments and in the MS and MA treatments without a significant reduction in pepper fruit yield. By promoting early fruit set and harvest, and bearing in mind the cumulative gross returns, mixing pepper and cassava enhanced the value of the vegetable, as early fresh pepper fruits command a premium price. It is concluded that pepper can be grown between cassava rows to provide a suitable environment for growth, but that this depends on the cassava cultivar. Using the less tall early cassava cultivar, with a relatively moderate leaf area index in a mixture with pepper is therefore recommended.
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Kusse, Kutoya. "Major Root and Tuber Crops Production in South Omo Zone, Southern Ethiopia." Current Agriculture Research Journal 9, no. 2 (August 31, 2021): 74–82. http://dx.doi.org/10.12944/carj.9.2.02.
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Increasing production and productivity of agriculture in general and root and tuber crops in particular require a strong linkage between the agricultural and non-agricultural sectors. The growing in agriculture sector does not occur without non-agricultural sectors. The major root and tuber crops production and productivity in South Omo Zone, Southern Ethiopia is very low in relation to the land coverage under the crops, due to poor and under recommended rate of improved agricultural technology utilization and low skill of management and related practices by the producers. To solve these root and tuber related problems and increase the production and productivity of the crops, strong and result based farmers training centers and interlinked research extension system are important and strongly interconnected . This study was conducted in five districts of South Omo Zone namely Debub Ari from agricultural based, Malle and Bena-Tsemay from agro-pastoral, Hammer, and Dasenech from pastoral. The districts are selected purposively based on root and tuber crop production potential. The result shows that the area coverage, production and productivity of the major root and tuber crops decreases from time to time and their diseases and pests increases thoroughly. Farmers in the study area should use disease resistance varieties and the production inputs at a recommended rate and time. The major root and tuber crops that are grown in the study area are sweet potato (Ipomoea batatas), potato (Solanum tuberosum), cassava (Manihot esculenta), taro (Colocasia esculenta), and enset (Ensete ventricosum).
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Ozarslandan, A., Z. Devran, N. Mutlu, and I. H. Elekcioglu. "First Report of Columbia Root-Knot Nematode (Meloidogyne chitwoodi) in Potato in Turkey." Plant Disease 93, no. 3 (March 2009): 316. http://dx.doi.org/10.1094/pdis-93-3-0316c.
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Columbia root-knot nematode, Meloidogyne chitwoodi Golden et al., was identified from potatoes, Solanum tuberosum L., collected from Nigde Province, Turkey in September 2006. Seed potatoes are the most likely source for this introduction. The nematode is currently found to be infecting potatoes grown in the Netherlands, Portugal, Belgium, Germany, the United States, Mexico, South Africa, and Argentina. M. chitwoodi acquired a quarantine status in Europe (1) because of its potential to become established worldwide and its high damage probability. Some countries prohibit import of both seed and table stock potatoes originating in states known to harbor M. chitwoodi. Lesions on the potatoes had discrete brown coloration with white central spots in the outer 1 cm of the tuber flesh. Female nematode densities averaged 3 to 5 per cm2 of a potato section beneath the lesions. Nematodes were morphologically identified as M. chitwoodi based on the perineal pattern of mature females and the tail shape of juveniles. Using PCR-restriction fragment length polymorphism of the 18S region (3) and the mtDNA COII-16S rRNA region (2) and intergenic spacer region between the 5S and 18S genes (4), individual juveniles were identified as M. chitwoodi based on their restriction fragment patterns. To our knowledge, this is the first report of Columbia root-knot nematode infecting potatoes in Turkey. The distribution of this nematode in potato fields throughout Turkey should be determined. References: (1) L. J. M. F. Den Nijs et al. Nematology 6:303, 2004. (2) T. O. Powers and T. S. Harris. J. Nematol. 25:1, 1993. (3) T. O. Powers et al. J. Nematol. 37:226, 2005. (4) J. Wishart et al. Phytopathology 92:884, 2002.
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Jansen van Vuuren, P. J. "NEW ORNAMENTAL CROPS IN SOUTH AFRICA." Acta Horticulturae, no. 397 (March 1995): 71–84. http://dx.doi.org/10.17660/actahortic.1995.397.5.
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Bester, C., L. M. Blomerus, and R. Kleynhans. "DEVELOPMENT OF NEW FLORICULTURE CROPS IN SOUTH AFRICA." Acta Horticulturae, no. 813 (March 2009): 67–72. http://dx.doi.org/10.17660/actahortic.2009.813.6.
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Luziatelli, Gaia, Marten Sørensen, and Sven-Erik Jacobsen. "Current uses of Andean Roots and Tuber Crops in South American gourmet restaurants." International Journal of Gastronomy and Food Science 22 (December 2020): 100270. http://dx.doi.org/10.1016/j.ijgfs.2020.100270.
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Swanepoel, K. M., and W. G. Alberts. "Species with potential for Industrial Crops in South Africa." South African Journal of Botany 76, no. 2 (April 2010): 404. http://dx.doi.org/10.1016/j.sajb.2010.02.047.
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Melkegna, Tamene Hailu, Ashok Kumar Chaubey, Sunday Adesunloye Jonah, Yusuf Aminu Ahmed, and Nuruddeen Abubakar. "Essential and trace elements status in the indigenous Ethiopian tuber crops." Radiochimica Acta 108, no. 1 (December 18, 2019): 51–56. http://dx.doi.org/10.1515/ract-2018-3072.
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Abstract The objective of the study is multi elemental analysis of four indigenous Ethiopian tuber crops using instrumental neutron activation analysis (INAA) technique in order to get scientific evidences about the status of essential, trace and non-essential elemental compositions. The samples were collected from Southern and South-western parts of Ethiopia. The irradiation and measurement were performed by using irradiation and counting facilities of the Nigeria Nuclear Reactor-1 (NIRR-1) and a HPGe detector setup at the Centre for Energy Research and Training (CERT), Ahmadu Bello University (ABU), Zaria, Nigeria. A total of 17 elements were determined at various concentration levels. The highest concentrations of K, Mg, Mn and Zn were found in Colocasia esculenta (L.) Schott, whereas; the concentrations of essential and trace elements; Ca, K, Mg, Na, Cl, Mn, and Zn were found to be high in the native Coccinia abyssinica (Lam.) Cogn tuber. The estimated daily intake values of the constituent elements from the consumption of these crops are below upper tolerable limits set by international organizations such as WHO and FAO.
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Nasruddin, Andi, and Laurence A. Mound. "First record of Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) severely damaging field grown potato crops in South Sulawesi, Indonesia." Journal of Plant Protection Research 56, no. 2 (April 1, 2016): 199–202. http://dx.doi.org/10.1515/jppr-2016-0023.
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AbstractGreenhouse whitefly, Trialeurodes vaporariorum Westwood was reported for the first time in the South Sulawesi Province of Indonesia, and is causing significant damage to field grown potato crops. In an insecticide trial, the tuber yield in infested, untreated plants was reduced by 39%, and the plants had an average number of 68 adult whiteflies per leaflet.
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Ndirika, Victor I. O., and André J. Buys. "Intermediate Agricultural Processing Technologies for Cereal Crops in South Africa." Journal of Sustainable Agriculture 28, no. 4 (October 5, 2006): 69–79. http://dx.doi.org/10.1300/j064v28n04_07.
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SCOONES, IAN. "Mobilizing Against GM Crops in India, South Africa and Brazil." Journal of Agrarian Change 8, no. 2-3 (April 2008): 315–44. http://dx.doi.org/10.1111/j.1471-0366.2008.00172.x.
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Toit, L. J. du, J. T. Burger, A. McLeod, M. Engelbrecht, and A. Viljoen. "Iris yellow spot virus in Onion Seed Crops in South Africa." Plant Disease 91, no. 9 (September 2007): 1203. http://dx.doi.org/10.1094/pdis-91-9-1203a.
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In December 2006, symptoms typical of iris yellow spot caused by Iris yellow spot virus (IYSV; genus Tospovirus, family Bunyaviridae) were observed on scapes (seed stalks) in an onion (Allium cepa L.) seed crop in the Klein Karoo of the Western Cape Province, South Africa. Symptoms included diamond-shaped chlorotic or necrotic lesions on the scapes, some of which had ‘green-islands’ with nested diamond-shaped lesions, as well as indistinct, circular to irregular, chlorotic or necrotic lesions of various sizes. At the time symptoms were observed, approximately 5% of the scapes had lodged as a result of extensive lesions resembling those caused by IYSV. The crop was 2 to 3 weeks from harvest. Symptomatic tissue from two plants (two samples from one plant and four samples from the other plant) was tested for IYSV by reverse-transcriptase (RT)-PCR. Total RNA was extracted from symptomatic scape tissue with the SV Total RNA Isolation System (Promega, Madison, WI) according to the manufacturer's instructions. First strand cDNA was synthesized with the RevertAid H Minus First Strand cDNA Synthesis kit (Fermentas Inc., Hanover, MD), followed by PCR amplification with primers IYSV-For (TGG YGG AGA TGY RGA TGT GGT) and IYSV-Rev (ATT YTT GGG TTT AGA AGA CTC ACC), which amplify the nucleocapsid (NP) gene of IYSV. An amplicon of expected size (approximately 750 bp) was observed for each of the symptomatic plants assayed and was sequenced. Comparison of the sequence (GenBank Accession No. EF579801) with GenBank sequences revealed 95% sequence identity with the NP gene of IYSV GenBank Accession No. EF419888, with eight amino acid differences. The known geographic distribution of IYSV in onion bulb or seed crops has increased rapidly in recent years in many areas of the world (1). To our knowledge, this is the first confirmation of IYSV in South Africa. Approximately 6,100 ha of onion bulb crops are grown annually in South Africa in the Western Cape, Kwazulu Natal, Limpopo, and Northern Cape provinces, and 600 ha of onion seed crops are grown primarily in the semi-arid regions of the Western Cape. Examination of an additional 10 onion seed crops in the Klein Karoo during January 2007 revealed the presence of iris yellow spot in three more crops at approximately 5% incidence in each crop. The four symptomatic crops had all been planted as bulb-to-seed crops, using vernalized bulbs produced on the same farm. This suggests that IYSV may have been disseminated into the seed crops on the vernalized bulbs, either as infected bulb tissue or in viruliferous thrips on the bulbs. Reference: (1) D. H. Gent et al. Plant Dis. 90:1468, 2006.
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Allemann, J., S. M. Laurie, S. Thiart, H. J. Vorster, and C. H. Bornman. "Sustainable production of root and tuber crops (potato, sweet potato, indigenous potato, cassava) in southern Africa." South African Journal of Botany 70, no. 1 (March 2004): 60–66. http://dx.doi.org/10.1016/s0254-6299(15)30307-0.
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Manners, Rhys, Elke Vandamme, Julius Adewopo, Philip Thornton, Michael Friedmann, Sebastien Carpentier, Kodjovi Senam Ezui, and Graham Thiele. "Suitability of root, tuber, and banana crops in Central Africa can be favoured under future climates." Agricultural Systems 193 (October 2021): 103246. http://dx.doi.org/10.1016/j.agsy.2021.103246.
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Venter, S. L., E. Van den Heever, J. Allemann, and J. Viljoen. "POTENTIAL VEGETABLE AND MEDICINAL USES OF TRADITIONAL CROPS IN SOUTH AFRICA." Acta Horticulturae, no. 523 (May 2000): 25–28. http://dx.doi.org/10.17660/actahortic.2000.523.2.
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McDonald, Alexander, Hendrika Fourie, and Gideon Loots. "Plant-parasitic nematodes in field crops in South Africa. 6. Soybean." Nematology 3, no. 5 (2001): 447–54. http://dx.doi.org/10.1163/156854101753250773.
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AbstractTwelve plant-parasitic nematode genera and 25 species were identified in soil and root samples collected from 17 localities in the soybean production areas of South Africa during the 1995/96 season. Predominant endoparasites found included Meloidogyne incognita, M. javanica, M. hapla, M. ethiopica, Pratylenchus zeae and P. brachyurus. Meloidogyne species occurred in 91% of all root samples, P. zeae in 87% and P. brachyurus in 33%. The occurrence of the three predominant endoparasites was not restricted to sandy soil, but they were also prevalent in soils with high clay contents. Other endoparasitic nematode species were Pratylenchus crenatus, P. teres, P. neglectus, P. thornei, Rotylenchulus parvus and Ditylenchus africanus. Nematodes found in soil included Helicotylenchus dihystera and Scutellonema brachyurus, which occurred in 78 and 71%, respectively, of all soil samples. Other nematodes found in soil samples were Helicotylenchus pseudorobustus, H. digonicus, H. microcephalus, Scutellonema truncatum, Rotylenchus unisexus, Mesocriconema sphaerocephalum, Paratrichodorus minor, Longidorus pisi, Xiphinema vanderlindei, X. elongatum and Tylenchorhynchus goffarti. Highest prominence values (PV) for Meloidogyne species were recorded on cultivars Prima, Bakgat, Tamboti, Hutcheson and Knap and the lowest on cultivars PAN812, SCS1, Nyala, Gazelle and A7119. Eight nematode genera and 19 species extracted during this study are reported for the first time in association with soybean in South Africa.
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Monteiro, Rodrigo Otávio Câmara, Jokastah Wanzuu Kalungu, and Rubens Duarte Coelho. "Irrigation technology in South Africa and Kenya." Ciência Rural 40, no. 10 (October 29, 2010): 2218–25. http://dx.doi.org/10.1590/s0103-84782010005000175.
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This paper reviews various irrigation technologies in both South Africa and Kenya that enable improvements in their socio-economic conditions. The two countries are located in semi-arid areas that experience extreme fluctuations in the availability of rain water for plant growth. Population growth exceeds the ability to produce food in numerous countries around the world and the two countries are not an exception. This experiment examined the constraints that farmers face and the role of government and nongovernmental organization in the uptake of modern technologies for irrigation. Detailed mechanisms and options to secure sustainable irrigation which are economically viable are considered. Despite the higher production of cereals and grains, fruits, and flowers also thrive in the two countries. Total irrigated area, crops grown and irrigation systems used in the two countries are discussed.
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Ganesh, S. P., I. P. Mohammad, A. K. Meena, and R. Swaminathan. "Diversity and seasonal incidence of insect pest complex of tropical tuber crops in South-Western Rajasthan." Journal of Entomological Research 41, no. 1 (2017): 85. http://dx.doi.org/10.5958/0974-4576.2017.00014.7.
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Prayudyaningsih, Retno, and Nursyamsi Nursyamsi. "DIVERSITY OF TUBER CROPS AND ARBUSCULAR MYCORRHIZAE FUNGI (AMF) UNDER COMMUNITY FOREST STAND IN SOUTH SULAWESI." Jurnal Penelitian Kehutanan Wallacea 4, no. 1 (April 30, 2015): 81. http://dx.doi.org/10.18330/jwallacea.2015.vol4iss1pp81-92.
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Truter, M., and F. C. Wehner. "Anastomosis Grouping of Rhizoctonia solani Associated with Black Scurf and Stem Canker of Potato in South Africa." Plant Disease 88, no. 1 (January 2004): 83. http://dx.doi.org/10.1094/pdis.2004.88.1.83b.
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Rhizoctonia disease (black scurf of tubers and stem canker) of potato (Solanum tuberosum L.) caused by Rhizoctonia solani Kühn was first recorded in South Africa in 1918 (3). Although the sclerotial form on tubers is one of the most common potato diseases in the country, it is not known which anastomosis groups (AGs) of R. solani are involved. Between 1999 and 2001, R. solani was isolated from 28 plant and 56 soil samples collected in 7 (Eastern Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, Northern Cape, and Sandveld) of the 14 potato-production regions of South Africa and screened for hyphal anastomosis with tester strains of R. solani AG-1 to AG-10 according to Carling et al. (1). Of the 411 isolates from tubers with black scurf symptoms, 408 were AG-3 and three were AG-5. Symptomless tubers yielded two AG-3 isolates and three AG-5 isolates. Of 39 isolates from symptomatic stems and roots, 32 were AG-3, five were AG-4, and two were AG-5. Of the 127 isolates obtained from soil, 86, 28, 7, 3, and 3 were AG-3, AG-4, AG-5, AG-7, and AG-8, respectively. More than one AG was isolated from five of the seven regions. Virulence of 40 isolates representative of the above AGs was determined in triplicate on sprouts growing from seed tubers of potato cultivar Up-to-Date in a sand/soil mixture as described by Carling and Leiner (2) but using cultures grown in cornmeal/sand instead of colonized agar disks as inoculum. Damage to sprouts (lesions, girdling, and death) was assessed after 28 days at 16 to 28°C according to the 0 to 4 rating scale (2). Chi-square analysis of the data indicated that AG-3 was the most virulent, with isolates from sclerotia on tubers and lesions on stems more aggressive than those from symptomless tubers or soil. AG-4 and AG-5 caused significantly less disease than AG-3, but none of the AG-7 and AG-8 isolates showed any virulence to potato sprouts. References: (1) D. E. Carling et al. Phytopathology 77:1609, 1987. (2) D. E. Carling and R. H. Leiner. Phytopathology 80:930, 1990. (3) E. M. Doidge. S. Afr. Fruit Growers 5:6, 1918.
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Moodley, Vaneson, Augustine Gubba, and Paramu L. Mafongoya. "A survey of whitefly-transmitted viruses on tomato crops in South Africa." Crop Protection 123 (September 2019): 21–29. http://dx.doi.org/10.1016/j.cropro.2019.05.018.
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Muthoni, Jane, and Hussein Shimelis. "Heat and drought stress and their implications on potato production under dry African tropics." SEPTEMBER 2020, no. 14(9):2020 (September 20, 2020): 1405–14. http://dx.doi.org/10.21475/ajcs.20.14.09.p2402.
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The two most important abiotic factors affecting potato productivity in many areas of the world and especially in the dry African tropics are drought and high temperature. The situation is worsened by global warming. High temperature and drought reduce not only yields but also quality of potatoes. The effects of drought depend on the genotype, timing, duration and severity of the stress; plant emergence and tuberization are two critical periods when water stress most affects the final tuber yield. The susceptibility of potato crops to high temperature largely depends on genotype, development stage and stress duration; tuber initiation and bulking are critical stages. High temperature, particularly high night temperature, is reported to delay tuber induction, prolong tuber setting, and delay the onset of rapid tuber growth. The optimum soil temperature range for tuber initiation and tuber growth is 15–20 0C, and the colder the soil temperature, the more rapid the initiation of tubers and the greater the number of tubers formed. At high temperature more photoassimilates are partitioned to the vegetative parts than tubers resulting in acceleration of haulm growth and inhibition of tuber initiation and growth. In tropical Africa, potato production is moving to the dry mid and low altitudes due to high population pressure in the moist highlands. In these dry areas, potato production is facing the double tragedy of high temperature and water stress. This has led to low yields and poor quality since there is no available commercial potato variety which is tolerant to high temperature and water stress. Breeding for heat and drought tolerance in potatoes is hard because in most cases, especially in dry tropics, these two conditions occur concurrently. In addition, the two traits are polygenic with low inheritance making conventional breeding difficult; more progress could be achieved through molecular breeding and/or genetic engineering.
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Moodley, Vaneson, Augustine Gubba, and Paramu L. Mafongoya. "Emergence and Full Genome Analysis of Tomato Torrado Virus in South Africa." Viruses 12, no. 10 (October 15, 2020): 1167. http://dx.doi.org/10.3390/v12101167.
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Emerging pests and diseases are a major threat to food production worldwide. In a recent survey, Tomato torrado virus (ToTV) was identified on tomato crops in the Limpopo province of South Africa and a first report of the disease was published. In this follow-up study, the full genome sequence of a tomato-infecting isolate of ToTV from South Africa was elucidated. High-throughput sequencing was used to generate the full genome of ToTV infecting tomato crops in South Africa. The longest contig obtained for the RNA-1 and RNA-2 genome of ToTV was comprised of 7420 and 5381 nucleotides (nt), respectively. Blast analysis of the RNA-1 sequence of ToTV from South Africa (ToT-186) matched 99% to a Spanish and Polish isolate; the RNA-2 segment of ToTV from South Africa (ToT-186) matched 99% to ToTV isolates from Italy and Poland, respectively. The information presented in this study will go a long way towards better understanding the emergence and spread of ToTV and devising sustainable management of ToTV diseases.
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Siwela, Muthulisi, Kirthee Pillay, Laurencia Govender, Shenelle Lottering, Fhatuwani N. Mudau, Albert T. Modi, and Tafadzwanashe Mabhaudhi. "Biofortified Crops for Combating Hidden Hunger in South Africa: Availability, Acceptability, Micronutrient Retention and Bioavailability." Foods 9, no. 6 (June 21, 2020): 815. http://dx.doi.org/10.3390/foods9060815.
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In many poorer parts of the world, biofortification is a strategy that increases the concentration of target nutrients in staple food crops, mainly by genetic manipulation, to alleviate prevalent nutrient deficiencies. We reviewed the (i) prevalence of vitamin A, iron (Fe) and zinc (Zn) deficiencies; (ii) availability of vitamin A, iron and Zn biofortified crops, and their acceptability in South Africa. The incidence of vitamin A and iron deficiency among children below five years old is 43.6% and 11%, respectively, while the risk of Zn deficiency is 45.3% among children aged 1 to 9 years. Despite several strategies being implemented to address the problem, including supplementation and commercial fortification, the prevalence of micronutrient deficiencies is still high. Biofortification has resulted in the large-scale availability of βcarotene-rich orange-fleshed sweet potatoes (OFSP), while provitamin A biofortified maize and Zn and/or iron biofortified common beans are at development stages. Agronomic biofortification is being investigated to enhance yields and concentrations of target nutrients in crops grown in agriculturally marginal environments. The consumer acceptability of OFSP and provitamin A biofortified maize were higher among children compared to adults. Accelerating the development of other biofortified staple crops to increase their availability, especially to the target population groups, is essential. Nutrition education should be integrated with community health programmes to improve the consumption of the biofortified crops, coupled with further research to develop suitable recipes/formulations for biofortified foods.
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Vereijssen, J., A. M. Barnes, N. A. Berry, G. M. Drayton, J. D. Fletcher, J. M. E. Jacobs, N. Jorgensen, et al. "The rise and rise of Bactericera cockerelli in potato crops in Canterbury." New Zealand Plant Protection 68 (January 8, 2015): 85–90. http://dx.doi.org/10.30843/nzpp.2015.68.5871.
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Tomato potato psyllid (TPP) Bactericera cockerelli (Scaron;ulc) (Hemiptera Triozidae) was first recorded in the North Island of New Zealand in 2006 Three years later the insect was found in the Oamaru area (South Island) Over the years there has been a rise in TPP numbers trapped in potato crops in Canterbury (South Island) Recently increased prevalence and severity of foliar and tuber symptoms related to plant infection with Candidatus Liberibacter solanacearum (CLso) vectored by TPP have been observed in trials and in commercial potato crops Moreover in the 201314 season the resulting zebra chip disease was observed for the first time in tubers at a processing plant in Canterbury It is concluded that Canterbury has a landscape where hosts are available yearround and a climate that does not seem to hinder TPP development The aim of this paper is to present a stocktake of TPP in Canterbury
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Cheteni, Priviledge. "Smallholder farmers’ awareness of biofuel crops in the Eastern Cape Province, South Africa." Environmental Economics 7, no. 3 (October 21, 2016): 75–80. http://dx.doi.org/10.21511/ee.07(3).2016.09.
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In this study, 157 smallholder farmers from the OR Tambo and Chris Hani district municipality in South Africa were purposively sampled to participate in a survey. The objective was to identify the factors that influence smallholder farmers’ awareness of biofuel crops. Using a binary logistic model, it was found that the variables: gender, household income, membership in association, land utilization and qualification were statistically significant in influencing farmers’ awareness of biofuel crops. Therefore, it is recommended that the South African government should identify the smallholder farmers targeted for the biofuel program by their social status, as pointed in this study. Keywords: awareness, binary model, biofuel industrial policy, energy, shared growth initiative, smallholder farmers. JEL Classification: Q1, Q2, Q4, Q5
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Okonya, Joshua, Walter Ocimati, Anastase Nduwayezu, Déo Kantungeko, Nicolas Niko, Guy Blomme, James Legg, and Jürgen Kroschel. "Farmer Reported Pest and Disease Impacts on Root, Tuber, and Banana Crops and Livelihoods in Rwanda and Burundi." Sustainability 11, no. 6 (March 15, 2019): 1592. http://dx.doi.org/10.3390/su11061592.
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Biotic constraints cause major crop losses and, hence, food insecurity in sub-Saharan Africa. This study documented the popularity, production constraints, pests and diseases, farmers’ perceptions on the severity of biotic constraints and the impact of related crop losses on household food security for the key root, tuber and banana (RTB) crops (cassava, potato, sweetpotato and banana). Farmer interviews were conducted in 2014 covering 811 households in Rwanda and Burundi. Farmers were asked to list their RTB crop production constraints, name insect pests and diseases of RTB crops, estimate crop loss due to pests and diseases, and mention if their household experienced any form of food insecurity due to pests and diseases. Cutworms and late blight in potato, banana weevils and banana Xanthomonas wilt in banana, cassava whitefly and cassava mosaic disease in cassava, sweetpotato weevils, and sweetpotato virus disease in sweetpotato were the most predominant pests and diseases reported. Crop losses due to pests and diseases for sweetpotato, banana, potato and cassava were estimated at 26%, 29%, 33%, and 36%, respectively, in Rwanda and 37%, 48%, 38%, and 37% in Burundi. Pests and diseases reduce the profitability of RTB crops, threaten food security, and constitute a disincentive for investment. Sustainable and affordable integrated pest management packages need to be developed.
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Schwinghamer, M. W. "Survey of New South Wales Potato Crops for Potato Spindle Tuber Viroid with Use of a32P-DNA Probe." Plant Disease 70, no. 8 (1986): 774. http://dx.doi.org/10.1094/pd-70-774.
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Kfir, Rami. "Prospects for biological control of Chilo partellus in grain crops in South Africa." International Journal of Tropical Insect Science 21, no. 04 (December 2001): 275–80. http://dx.doi.org/10.1017/s1742758400008353.
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Abidoye, Babatunde O., and Edward Mabaya. "Adoption of genetically modified crops in South Africa: Effects on wholesale maize prices." Agrekon 53, no. 1 (January 2, 2014): 104–23. http://dx.doi.org/10.1080/03031853.2014.887907.
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Cloete, P. C., and E. F. Idsardi. "Consumption of Indigenous and Traditional Food Crops: Perceptions and Realities from South Africa." Agroecology and Sustainable Food Systems 37, no. 8 (September 14, 2013): 902–14. http://dx.doi.org/10.1080/21683565.2013.805179.
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Visagie, Melissa, Charlotte M. S. Mienie, Mariette Marais, Mieke Daneel, Gerrit Karssen, and Hendrika Fourie. "Identification of Meloidogyne spp. associated with agri- and horticultural crops in South Africa." Nematology 20, no. 4 (2018): 397–401. http://dx.doi.org/10.1163/15685411-00003160.
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Jaars, K., J. P. Beukes, P. G. van Zyl, A. D. Venter, M. Josipovic, J. J. Pienaar, V. Vakkari, et al. "Ambient aromatic hydrocarbon measurements at Welgegund, South Africa." Atmospheric Chemistry and Physics Discussions 14, no. 4 (February 17, 2014): 4189–227. http://dx.doi.org/10.5194/acpd-14-4189-2014.
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Abstract. Aromatic hydrocarbons are associated with direct adverse human health effects and can have negative impacts on ecosystems due to their toxicity, as well as indirect negative effects through the formation of tropospheric ozone and secondary organic aerosol that affect human health, crop production and regional climate. Measurements were conducted at the Welgegund measurement station (South Africa) that is considered to be a regionally representative background site. However, the site is occasionally impacted by plumes from major anthropogenic source regions in the interior of South Africa, which include the western Bushveld Igneous Complex (e.g. platinum, base metal and ferrochrome smelters), the eastern Bushveld Igneous Complex (platinum and ferrochrome smelters), the Johannesburg–Pretoria metropolitan conurbation (>10 million people), the Vaal Triangle (e.g. petrochemical and pyrometallurgical industries), the Mpumalanga Highveld (e.g. coal-fired power plants and petrochemical industry) and also a region of anti-cyclonic recirculation of air mass over the interior of South Africa. The aromatic hydrocarbon measurements were conducted with an automated sampler on Tenax-TA and Carbopack-B adsorbent tubes with heated inlet for one year. Samples were collected twice a week for two hours during daytime and two hours during night-time. A thermal desorption unit, connected to a gas chromatograph and a mass selective detector was used for sample preparation and analysis. Results indicated that the monthly median total aromatic hydrocarbon concentrations ranged between 0.01 to 3.1 ppb. Benzene levels did not exceed local air quality standards. Toluene was the most abundant species, with an annual median concentration of 0.63 ppb. No statistically significant differences in the concentrations measured during daytime and night-time were found and no distinct seasonal patterns were observed. Air mass back trajectory analysis proved that the lack of seasonal cycles could be attributed to patterns determining the origin of the air masses sampled. Aromatic hydrocarbon concentrations were in general significantly higher in air masses that passed over anthropocentrically impacted regions. Interspecies correlations and ratios gave some indications of the possible sources for the different aromatic hydrocarbons in the source regions defined in the paper. The highest contribution of aromatic hydrocarbon concentrations to ozone formation potential was also observed in plumes passing over anthropocentrically impacted regions.
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Mufungizi, A. A., W. Musakwa, and T. Gumbo. "A LAND SUITABILITY ANALYSIS OF THE VHEMBE DISTRICT, SOUTH AFRICA, THE CASE OF MAIZE AND SORGHUM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2020 (August 21, 2020): 1023–30. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2020-1023-2020.
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Abstract. Sustainable development goals (SDGs) 1 and 2 stand for “No poverty” and “Zero hunger” respectively. Achieving these goals cannot be separated from promoting sustainable agriculture and ensuring livelihoods, especially for rural communities. This study sought to determine the suitability of land for the cultivation of maize and sorghum crops in Vhembe District, South Africa. The study applied the Analytical Hierarchy Process (AHP) and the Weighted Linear Combination (WLC), multi-criteria decision-making techniques, for criteria weights calculations and suitability maps calculations respectively within a Geographic Information System (GIS) environment. Six criteria were used; Soil pH, Soil Structure, Rainfall, Maximum Temperature, Minimum Temperature and Elevation. A consistency ratio (CR) of 0.035 was obtained for maize criteria weights and 0.036 for sorghum criteria weights. The results revealed that only limited portions of the whole district are highly suitable for the cultivation of Maize with 15.01% and Sorghum with 19.39 of the land arable for farming. This suggests lower maize and sorghum crops yields in the district and the paper recommends more cultivation of other drought resistant crops other than maize and sorghum.
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Devaux, A., and A. J. Haverkort. "The Effects of Shifting Planting Dates and Mulching on Late Blight (Phytophthora infestans) and Drought Stress of Potato Crops Grown under Tropical Highland Conditions." Experimental Agriculture 23, no. 3 (July 1987): 325–33. http://dx.doi.org/10.1017/s001447970001721x.
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SUMMARYPotatoes (Solanum tuberosum L.) in central Africa are often grown between two rainy seasons to avoid late blight infection. The influence of planting date and setaria mulch treatment on soil temperature, soil humidity, late blight development, ground cover with green leaves, intercepted radiation and tuber yield of potato was studied in crops grown at 1850 m above sea level in Rwanda.The planting dates towards the end of the rainy season resulted in the best yields and these were considerably increased by mulching which retained soil moisture and reduced soil temperature so resulting in a better ground cover. Increased yields in the mulched plots seemed to be due to increased radiation interception rather than to better radiation use efficiency.
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Ebert, A. W., and A. J. G. van Gastel. "WEST AFRICA SEED DEVELOPMENT UNIT (WASDU): STRENGTHENING THE PRODUCTION AND MARKETING OF HEALTHY PLANTING MATERIALS OF ROOT AND TUBER CROPS." Acta Horticulturae, no. 517 (March 2000): 39–48. http://dx.doi.org/10.17660/actahortic.2000.517.4.
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