Literatura académica sobre el tema "Rice – Varieties – Niger"

This research was carried out to evaluate the health and quality of rice seed. The germination of seed and presence of rice seed related fungi were recorded and used to evaluate the effect of seed dressing chemicals on germination and vigor index over untreated rice seeds. Seven cultivars commonly grown in Kano, Kano State, Northwestern Nigera “FARO 52” (WITA), “FARO 44” (SIPI), “FARO 60” , (improved varieties), “Kwandala” , “Jamila” , Ex-china, and “JIF” (local varieties) were used in this study. The seed dressing chemicals used were Apron Star 42 WS, Dress Force 42WS and ZEB-Care 80%WP. This study was performed under three main tests, i.e dry inspection, blotter tests, agar plate and microscopic examination. The highest number of healthy seeds (94.16%) was recorded from “JIF” variety and lowest (64.77%) from “Jamila” . The highest number of deformed seeds was observed from variety “FARO 44” whereas the lowest noted on “JIF” . The identified fungi were Fusarium spp., Bipolaris oryzae, Aspergillus flavus, Curvularia lunata, Aspergillus niger, and Nigrospora oryzae., Rhizoctonia spp. and Rhizopus spp. Highest seed infection was recorded for A. flavus, A. niger, and Fusarium spp., and the least with C. lunata and N. oryzae. Treated seeds with Zeb-care (Mancozeb 80% WP), increased their vigor index over untreated by 62.78% and can be recommended as seed dressing chemical for optimun control of rice seed- borne pathogens.

A total of 20 rice varieties of BRRI dhan 56 to BRRI dhan 75 were collected from Bangladesh Rice Research Institute (BRRI) for seed quality analysis, detection and identification of fungi associated with seeds of selected rice varieties. Dry inspection indicated that the percentage of pure seeds ranged from 90 - 100. The highest percentage of pure seed was found in BRRI dhan 66 and BRRI dhan 70 (100) and lowest in BRRI dhan 68 (90). A total of 21 fungal species were isolated from the selected rice varieties following “Blotter and Tissue Planting” methods. They were Alternaria padwickii, A. tenuissima, Aspergillus flavus, A. fumigatus, A. niger, A. ochraceus, A. clavatus, A. terreus, Bipolaris sorokiniana, B. spicifera, Chaetomium globosum, Curvularia lunata, Drechslera oryzae, Fusarium sp.1, Fusarium sp. 2, Nigrospora sp., Penicillium sp., Pestalotiopsis guepinii, Rhizopus stolonifer, Syncephalastrum racemosum and Trichoderma viride. Among them Penicillium sp., Drechslera oryzae, Aspergillus ochraceus, A. flavus, A. fumigatus, A. niger and Fusarium sp.1 were predominant in most of the rice varieties. In Tissue Planting method Drechslera oryzae showed the highest mean per cent frequency (6.69) and lowest was in the Bipolaris sorokiniana (0.41). Maximum total fungal association was recorded in variety BRRI dhan 61 (156.79%) and minimum in BRRI dhan 66 (24.69%). In Blotter method Penicillium sp. showed the highest mean per cent frequency (7.56) and lowest was in Rhizopus stolonifer (1.71). Maximum total fungal association was recorded in BRRI dhan 63 (147.37%) and minimum in BRRI dhan 65 (19.21%). Germination percentage of seeds was highest in BRRI dhan 66 (88) followed by BRRI dhan 67 (82), BRRI dhan 74 (80) and lowest in BRRI dhan69 (24). The percentage of seedling mortality was highest in BRRI dhan 63 (42) and lowest in BRRI dhan 74 (8.0) followed by BRRI dhan 67 (10). Correlation coefficient and regression analysis indicated that prevalence of fungi has significant effect on seed germination and seedling mortality. The present research work suggests that out of 20 BRRI rice varieties, BRRI dhan 65, BRRI dhan 66, BRRI dhan 67 and BRRI dhan 74 showed better performances on the basis of percentage of pure seed, fungal association, seed germination and seedling mortality. Asiat. Soc. Bangladesh, Sci. 44(1): 79-89, June 2018

Twenty five fungal species, representing 13 genera were found to be associated with seeds of 20 varieties of rice (BRRI dhan 56 to BRRI dhan 75). Fungi were isolated following "Tissue planting" method and "Blotter method". The isolated fungi were Alternaria alternata, A. tenuissima, Aspergillus flavus, A. fumigatus, A. niger, A. ochraceus, A. terreus, Bipolaris multiformis, B. oryzae, B. sorokiniana, Chaetomium globosum, Curvularia lunata, Fusarium equiseti, F. fugikuroi, F. oxysporum, F. proliferatum, Microdochium fisheri, Nigrospora oryzae, Penicillium sp., Pestalotiopsis oxyanthi, Phanerochaete chrysosporium, Rhizopus stolonifer, Sarocladium oryzae, Syncephalastrum racemosum and Trichoderma viride. Dhaka Univ. J. Biol. Sci. 29(1): 75-86, 2020 (January)

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae represents a severe threat to rice cultivation in Mali. Characterizing the pathotypic diversity of bacterial populations is key to the management of pathogen-resistant varieties. Forty-one X. oryzae pv. oryzae isolates were collected between 2010 and 2013 in the major rice growing regions in Mali. All isolates were virulent on the susceptible rice variety Azucena; evaluation of the isolates on 12 near isogenic rice lines, each carrying a single resistance gene, identified six new races (A4 to A9) and confirmed race A3 that was previously reported in Mali. Races A5 and A6, isolated in Office du Niger and Sélingué, were the most prevalent races in Mali. Race A9 was the most virulent, circumventing all of the resistance genes tested. Xa3 controlled six of seven races (i.e., 89% of the isolates tested). The expansion of race A9 represents a major risk to rice cultivation and highlights the urgent need to identify a local source of resistance. We selected 14 isolates of X. oryzae pv. oryzae representative of the most prevalent races to evaluate 29 rice varieties grown by farmers in Mali. Six isolates showed a high level of resistance to X. oryzae pv. oryzae and were then screened with a larger collection of isolates. Based on the interactions among the six varieties and the X. oryzae pv. oryzae isolates, we characterized eight different pathotypes (P1 to P8). Two rice varieties, SK20-28 and Gigante, effectively controlled all of the isolates tested. The low association observed among races and pathotypes of X. oryzae pv. oryzae suggests that the resistance observed in the local rice varieties does not simply rely on single known Xa genes. X. oryzae pv. oryzae is pathogenically and geographically diverse. Both the races of X. oryzae pv. oryzae characterized in this study and the identification of sources of resistance in local rice varieties provide useful information to inform the design of effective breeding programs for resistance to bacterial leaf blight in Mali.

Mycotoxigenic fungi and relative mycotoxins contamination were monitored in Italian paddy rice samples both in field during the growing season and the first five months of storage. Three experimental fields, nine rice varieties and three sowing densities were considered; then, different lots of paddy rice were stored in warehouses at different temperature regimes. Fusarium spp. and Aspergillus spp. were found to be the fungi most likely to produce mycotoxins throughout the growing season. In particular, A. flavus and A. niger were found only rarely both in field and in post-harvest, while A. versicolor was always present although in low concentrations. Penicillium spp. strains were isolated sporadically and were found to be irrelevant in Italian rice fungal contamination. Sterigmatocystin (STC) was the main mycotoxin found in Italian rice, while aflatoxin (AFB1), deoxynivalenol (DON) and ochratoxin A (OTA) were rarely detected. Contamination generally increased from post-flowering to ripening; considering rice varieties, significant differences (p ≤ 0.01) were found in fungal contamination and STC production; no differences were observed between sowing densities. During storage, an increase in STC content was observed in higher temperature regimes, while all the other considered mycotoxins remained unchanged. These results indicated that contamination by STC, an emerging mycotoxin not legislatively regulated by the European Union, can be relevant in rice.

Seeds of rice were treated with Garlic (Allium sativum) clove extract @ 1:0, 1:1, 1:2 dilutions in water, allamanda (Allamanda cathartica) leaf extract @ 1:1, 1:2, 1:3 dilutions in water and Provax-200 @ 0.3% for controlling seed borne fungi, where the seed samples of three rice varieties viz. Katharee, Gutee Aus and Kalijira were collected from farmer’s storages of Bangladesh. The seed germination under control ranged from 64 to 77%, where treatments resulted up to 100% germination. The identified seed borne fungi of rice were Bipolaris oryzae, Curvularia oryzae, Fusarium oxysporum, F. moniliforme, Nigrospora oryzae, Aspergillus flavus, Aspergillus niger and Penicillium sp., where prevalence of Bipolaris oryzae (7.5%) and Fusarium moniliforme (8.3%) were the maximum. All the treatments significantly reduced the seed borne fungi up to 100% over the control, where Provax was found best and was statically similar to garlic (1:1) extract against seed borne pathogen of rice.DOI: http://dx.doi.org/10.3329/agric.v10i1.11064The Agriculturists 2012; 10(1): 46-50

Seeds of 15 hybrid rice varieties viz. Durber, Agomoni, Meghna, Hybrid super, Moyna, Tia, Gold, Aloron, Jagoron, Suborno, Safollo, Hira-1, Hira-2, Hira-4 and Hira-6 were collected from five different seed producing companies of Bangladesh. BAU-Biofungicide (3%), extracts of Garlic (1:1), Allamanda leaf (1:1) Bavistin (0.3%), Thiovit ( 0.3%) and Provax (0.3%) were used for treating seeds to improve quality of hybrid seeds of rice. The moisture content of seed samples ranged 12.20% to 14.37%, where highest moisture content was found in variety Meghna and lowest in variety Moyna. 1000-seed weight of seed samples ranged from 20.00 to 26.00g, where highest weight was recorded in Hira-4 and lowest was recorded both in Aloron and Hira-1. Seed health test revealed 11 different seed borne fungi viz. Bipolaris oryzae (0.0 to 25.5%), Fusarium moniliforme (0.00 to 3.0%), Fusarium oxysporum (0.0 to 18.0%), Aspergillus flavus (0.00 to 11.0%), Aspergillus niger (0.00 to 5.0%), Aspergillus candidus (0.00 to 15.0%), Penicillium spp. (0.0 to 7.0%) , Alternaria padwickii (0.0 to 1%), Alternaria tenuis (0.0 to 11.0%), Curvularia lunata (0.0 to 40.0%) and Nigrospora oryzae (0.0 to 4.0%) . Germination test resulted normal seedlings from 26.00 to 97.00%, where highest was recorded in variety Jagoron that treated with BAU-Biofungicide resulting highest increase in number of normal seedlings by 239.28% over untreated control. BAU-Biofungicide significantly decreased (upto 90.00%) formation of abnormal seedlings over untreated control. Moreover, BAU-Biofungicide increased up to 713.78% Vigor index over untreated control.Asian J. Med. Biol. Res. December 2015, 1(3): 406-415

The Earth's temperature is rising as a result of increased atmospheric concentrations of greenhouse gases. As the Earth warms, currently wet regions are expected to receive more rainfall, and currently dry regions receive less. Nigeria and indeed Northern Nigeria is not an exception. Crop production is one of the most vulnerable systems and heavily affected by climate change in Nigeria and more particularly in the Northern part of the country where the presence and prevalence of drought is mostly felt. Crops are mostly flooded and are rendered less productive by flood, in addition to extensive dependence on rainfed farming coupled with high poverty level of the people of the region. Major crops cultivated in the region include groundnuts, beans, cotton, soybeans, sesame, cashew nuts, mango, cassava, yam, gum arabic, maize (corn), melon, millet, , plantains, rice, sorghum, bananas, yams, pepper, coffee, carrots, sugarcane, soybeans, with major producing states of soybeans as Kaduna, Niger, Kebbi, Nasarawa, Kwara, Jigawa, Taraba, Borno, Benue, Bauchi, Sokoto, Plateau, Zamfara and Abuja FCT are now facing yield depreciation. Most of these crops are facing problems such as flower abortions, wrong flowering and fruiting time and generally low yields due to the effects of climate change. As rainfall becomes more variable, farmers no longer are able to rely on their knowledge of the seasonality of climatic variables. It is recommended that, series of awareness in terms of seminars, symposiums, farmers field days should be conducted to the farmers to enlighten them on the knowledge of modern techniques of crop production, such as the use of early maturating seeds, drought resistance varieties and more especially the use of irrigation in order to boost crop production in the region. Weather focused information should be made available to the farmers in the form of short message (SMS) in addition to informing them on weather both in print media.

<p style="text-align: justify;">Experimental conditions for leaf protoplast isolation and culture were optimised for <em>in vitro</em> plants deriving from shoot culture of two Tunisian grape varieties, Sakasly and Muscat d’Alexandrie (<em>Vitis vinifera</em> L.). The best yields were obtained from leaves of 4 to 5 weeks old <em>in vitro</em> plants, digested for 13 hours under 25 rpm agitation with an enzymatic mixture containing 0.25 % cellulase of <em>Aspergillus niger</em>, 0.25 % cellulase of <em>Penicillium funiculosum</em>, 0.5 % cellulysin of <em>Trichoderma viridae</em>, and 0.2 % macerozyme R-10 of <em>Rhizopus</em> sp. More than 50 % of the purified protoplasts had a diameter of 30-40 μm and were rich in chloroplasts. Best aptitude for cell division was found in protoplasts immobilised in sodium alginate layers at a density of 0.5x10⁶ cell/ml, cultivated in CPW-13 medium containing 4 mg/l of NOA and 0.88 mg/l of TDZ. The variety Muscat d’Alexandrie gave better yield whereas Sakasly showed better cell division rates. Formation of micro and macrocallus have been obtained, but the oxidation of the medium has to be solved in order to promote plant regeneration.</p>

Introduction: Rice (Oryza sativa L.) is the second best essential cereal crop of the world as well as of Pakistan. There are various fungal pathogens that attack on rice and cause various rice diseases. Methods: Therefore, the present experiments were done to isolated different fungi associated with seeds, stems, and leaves of commercially grown rice varieties and of mainly isolated species. Results: Several fungi, namely, Magnaporthe oryzae, Curvularia lunata, Helminthosporium oryzae, Fusarium moniliforme, Alternaria alternata, Nigrospora oryzae, and Aspergillus niger were isolated from seeds, stems, and affected leaves of rice. Conclusion: In our research, the frequency of fungal mycoflora on rice has been calculated and the maximum isolates of Fusarium spp. have been found.

Rice is a staple food in many West African countries, including Niger. However, both regional and national rice production have failed to meet demand due to several constraints, among which is the Rice yellow mottle virus (RYMV). Moreover, attempted intensification of rice cultivation and the introduction of modern cultivars are encouraging farmers towards abandoning local landraces for high yielding, but often susceptible varieties. The study was primarily oriented towards rice pre-breeding, and identifying priorities for rice breeding in Niger in relation to farmers' preferences and their environment. A secondary aim was the development and evaluation (for release at the regional level) of new breeding lines with resistance to RYMV. This study aimed to: 1) Establish farmers' perception of rice varieties as well as the main constraints on rice production in Niger and particularly those posed by RYMV; 2) Create a collection of rice species from Niger for ex- situ conservation, and to determine the phenotypic variability within this collection; 3) Determine the genetic diversity and population structure of the collection; 4) Screen the collection for resistance to RYMV, so that new sources of resistance could be detected; 5) Improve five elite varieties from West Africa for resistance to RYMV using marker-assisted selection (MAS). The germplasm collection and PRA of this study were conducted in 2008 and 2009 in Niger, while the field and the laboratory researches were conducted in 2008 and 2009 at the Africa Rice Center (AfricaRice) in Benin. For the PRA, data was obtained from a semi-structured group discussion carried out in 14 villages, individual questioning of 153 farmers and visits to farmers' field and storage facilities. The local farmers' union was the only formal seed dissemination system. Seed exchanges between farmers and the use of seeds from previous harvests were important. The RYMV and the bacterial leaf blight (BLB) were cited as the prevalent biotic stresses in the irrigated agrosystem, where the varieties IR1529-680-3 and Waihidjo were found to be the most popular. Flood, birds and hippopotamus were the most damaging agents in the lowland cropping system, and the landrace Degaulle/ D5237 was the preferred variety. Apart from the yield, farmers preferred varieties with good grain quality (milling quality and good taste), high market value, stress tolerance (drought, flood, disease, birds, rodents), and those recommended by the local farmers' association. These findings should be included in breeding goals, seed production and dissemination systems. During collection, a total of 270 rice accessions were assembled, comprising the two cultivated rice species Oryza sativa L. and O. glaberrima Steud. and its two wild relatives Oryza barthii A. Chev. and O. longistaminata Chev. et Roehr. The region of the Niger River and its tributary (the Dallol Maouri) provided the majority (80.7%) of the accessions. Apart from a few wild O. barthii accessions, the accessions found around Lake Chad and the Komadougou river (South-East) were also collected in the Niger River area. Farmers' naming and ecological classification of rice varieties was generally consistent. Three major phenotypic groups were found during the field trials, and the overall phenotypic variability of the collection (as measured by the Shannon-Weaver Diversity Index) was relatively high. There was no significant difference in diversity between the main eco-geographical zones of collection, as well as between the identified phenotypic groups, suggesting a high level of germplasm exchange between the regions in Niger. From the collection, 264 accessions were genotyped from the collection using 18 well distributed SSR markers and two main genetic compartments were detected, comprising O. sativa subsp. indica varieties and O. glaberrima and its wild relative O. barthii and O. longistaminata. The O. sativa group in Niger was divided into irrigated and floating rice, bound by lowland rice. The wild progenitor O. barthii was widespread but without any clear genetic differentiation from O. glaberrima, probably due to the presence of admixtures within the collected samples of O. barthii. Allelic diversity was relatively high, despite the geographical distance from the centre of domestication of African rice, and the points of entry of Asian rice to Africa. The findings reflect the underuse of Niger's rice landraces genetic potential for rice breeding, given that all the "improved" varieties released during the last 25 years in Niger were clustered together on the dendrogram. The response of a set of the rice collected from Niger and some accessions from Mali to inoculation by RYMV was evaluated using five different virus isolates from Niger (3), Benin (1) and Burkina Faso (1). All rice varieties were susceptible to the disease. However, depending on the virus strain, a few O. glaberrima accessions displayed partial resistance, similar to the highly resistant TOG5681. Allelic research based on primers derived from the RYMV1 gene revealed one accession with allele rymv1-3, and two accessions with allele rymv1-4, and one accession with a different resistance gene. The implications of the finding were discussed and a strategy proposed for breeding varieties with a comprehensive resistance to RYMV. After three generations of backcrossing, the major resistance gene of the variety Gigante was successfully introgressed into five elite rice varieties of West Africa by Marker-Assisted Backcross (MABC). The newly developed BC3F3 progenies were screened for resistance to RYMV in farmers' fields in Guinea and Mali and also under controlled conditions in a screenhouse in Benin. As shown by low virus content and level of disease incidence, low tiller number and plant height reduction, the transferred gene was fully functional in the new genetic background. Moreover, some lines also displayed a high level of resistance to rice blast (Pyricularia oryzae) and stem borer infestation in Guinea. Four of those lines are in the second year of multi-location trial in seven West African countries. Therefore, effective deployment of the newly developed varieties, coupled with good cultural practices, should reduce the damaging effects of RYMV in lowland and irrigated rice cropping systems and thereby increase the income of small scale farmers from rice cultivation.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.