Dissertations / Theses on the topic 'Improved varieties'

The International Potato Center (CIP) and Peruvian National Agricultural Research Institute (INIA) have invested a substantial amount of resources towards the development of improved potato varieties in Peru. These varieties are adaptable to the agro-ecologies of the Andes and have specific biotic and abiotic attributes. These efforts have led to the release of several prominent varieties including Canchan-INIA, Amarilis, Unica, Serranita and others. A 2013 household survey conducted by CIP was used to describe the diffusion of improved potato varieties in Peru. These data were also used to identify specific constraints to their adoption and dis-adoption. The assessment focused on a two-step adoption model, adoption and dis-adoption, by utilizing a Heckman Probit model to demonstrate two-steps of the adoption process. The Heckman Probit model was used to analyze variables affecting adoption and dis-adoption of improved varieties. Results suggest that adoption is region specific, time dependent, and in some cases relies on informal transmission methods. Risk to food insecurity and recurrent natural phenomena affect adoption and sometimes dis-adoption. Additionally, factors affecting a farmer's exposure to risk, such as information constraints and household head age, wealth, and social network were found to affect the adoption and dis-adoption of improved varieties.
Master of Science

Public agricultural research has been conducted in Africa for decades and has generated numerous crop technologies, while little is understood on how agricultural research affects the poor and vulnerable groups such as children, and how farmers' perceptions affect their adoption decisions. This dissertation helps fill this gap with three essays on adoption and impacts of improved maize varieties in rural Ethiopia. The first essay estimates poverty impacts. Field-level treatment effects on yield and cost changes with adoption are estimated using instrumental variable techniques, with treatment effect heterogeneity fully accounted for in marginal treatment effect estimation. A backward derivation procedure is then developed within an economic surplus framework to identify the counterfactual income distribution without improved maize varieties. Poverty impacts are estimated by exploiting the differences between the observed and counterfactual income distributions. Improved maize varieties have led to 0.8-1.3 percentage drop in poverty headcount ratio and relative reductions in poverty depth and severity. However, poor producers benefit the least from adoption due to their small land holdings. The second paper assesses the impacts on child nutrition outcomes. The conceptual linkage between maize adoption and child nutrition is first established using an agricultural household model. Instrumental variable (IV) estimation suggests the overall impacts to be positive and significant. Quantile IV regressions further reveal that such impacts are largest among the most severely malnourished. By combining a decomposition procedure with estimates from a system of equations, it is found that the increase in own-produced maize consumption is the major channel such impacts occur. The third paper explores how farmers' perceptions of crop traits affects their willingness to adopt improved maize varieties. Under a random utility framework, a mixed logit procedure is implemented to model farmer's adoption intention, where perceptions of key varietal traits are first identified, and then instrumented using a control function approach to account for potential endogeneity. Perceived yield is found to be the most important trait affecting farmers' adoption intention. Further, yield perceptions among previous adopters appear to be affected by within-village peer effects rather than the real crop performance.
Ph. D.

"Maize is the most important food crop in Mozambique. However, maize production is low and is cyclically impaired due to abiotic stresses such as recurrent droughts (particularly in the arid and semi-arid areas), soil infertility, floods, and cyclones events. Biotic stresses, such as pests and diseases, also affect food production. Altogether, these constraints lead to food insecurity and the need for humanitarian food aid from local and international communities. (...)"
N/A

Cassava is the main staple crop in Nigeria. Using primary data from four south eastern states in Nigeria, the study assessed the gender impacts of improved cassava varieties. Comparative statistical analysis reveals that total female labor is higher than total male in cassava production, processing and marketing. Women spend more labor days than males for planting, weeding, harvesting, marketing and processing. The total female family labor is higher for adopters of new improved cassava varieties. There is however lower family labor input for both male and female adopters for clearing and plowing which are normally done by men. Significant determinants of female labor supply are number of children in the household, percent of females in the household providing labor on the farm, area under improved cassava varieties and total land area. There is a positive unexpected relationship between total female labor supply and number of children. For each of the decision making variables, there is a significant association between the gender of the spouse and the decision made except for the decision on family labor allocation. Probit results show a significant decrease in the probability that the wife makes the decision for family labor allocation, what inputs to buy and borrowing and traditional cassava income control with adoption. Results indicate that both men and women spend their income on services directly linked to the householdâ s welfare. More than half of the women ranked food as number one.
Master of Science

Common beans are one of the most important food and cash crops for most Malawians. The insufficient production of the crop in the country coupled with low yields has made scientists give much interest to the crop so that they can address the constraints to the productivity problems. In this regard, breeders have been engaged in the development and release of improved varieties of common beans which in most cases are disease resistant, high yielding, drought resistant, and fast cooking. Therefore it is the interest of this study to find the reasons why productivity of the crop is still low despite the release of the improved varieties. The study adopted contingent valuation (CV), a method frequently used to assess willingnessto- pay of people for non-market goods or services and this was applied to assess farmer’s willingness-to-pay for the new improved bean seed varieties which are high yielding. Double bounded dichotomous choice with an open ended follow-up format was used to obtain the household’s willingness-to-pay. In addition; the study reviewed the existing dissemination channels of bean seed to make recommendations with regard to seed supply. Descriptive statistics from the 132 households interviewed shows that the structural constraints to seed acquisition are compounded by farmers’ poverty. Otherwise, most farmers are aware of the existence of improved varieties of common bean seed and perceive that with the use of this seed, productivity can improve hence willing to pay for the good. The study is 95% confident that mean price farmers are willing to pay for improved common bean seed is between MK 527.78 and MK 591.92. Three major existing informal dissemination channels of bean seed were discovered in the study areas. Therefore there is a need for government to work in collaboration with NGOs towards ensuring a formal supply system of bean seed characterised by vertically organised production and dissemination of tested and approved seed varieties, and using strict quality control rules, so that farmers can be assured of accessing improved seed varieties. This will increase the nation’s food security.
Dissertation (MSc Agric)--University of Pretoria, 2013.
gm2014
Agricultural Economics, Extension and Rural Development
unrestricted

Cooperation-88 (C88) is a late blight resistant potato variety that was formally released in China in 2001 and has become popular in China's Yunnan Province. The International Potato Center (CIP) and Yunnan Normal University collaborated to produce the variety, which is one of CIP's most successful varieties. C88 is popular due to its high quality and taste, and it is used commonly in China's expanding potato chip processing market. The purpose of this study is to examine adoption of C88 in the Yunnan Province, its value chain, and economic impacts. The analysis indicates that C88 is still popular with 16.8% of the potato area in Yunnan devoted to this variety in late spring 2015. To examine factors affecting household decisions to adopt and the intensity of their adoption, village adoption, household adoption, and household intensity of adoption were assessed. A village's proximity to a metropolitan county was the most important factor explaining adoption and intensity of adoption. Households in villages closer to a metropolitan county disadopted at higher rates than those farther away. To quantify the economic benefits of C88 adoption, an economic surplus analysis was conducted. Total surplus changes ranged from $2 to 3 billion indicating significant economic benefits to consumers and producers in Yunnan.
Master of Science

The current world population is over 7.4 billion and expected to exceed 9 billion in 2040, causing a 70% increase in food demand. Global environmental degradation, in the form of salinization, pollution and global warming, has also reduced the availability of suitable arable land and water sources, contributing to promote crop improvement in order to increase the potential yields. Rice (Oryza sativa) is the most widely consumed staple food for a large proportion of the world population. Classical rice breeding programs use its natural variability to create new allelic combinations which are screened for selecting those presenting superior agronomic traits such as improved yield. Those improved lines are stabilized through inbreeding to maintain the phenotype in their progeny. Certified seed producers systematically select and propagate registered varieties year by year in order to maintain their uniformity and the original registered cultivar traits, since natural mutations, spontaneous breeding between varieties and alien grain contamination can introduce undesirable variability at this stage. Nowadays biotechnology is used to drive the improvement of rice traits such as increased yield and grain quality. Moreover it helps to rapidly bestow tolerance to biotic (diseases and insects) and abiotic (drought, salinity, cold temperatures, nutrients deficiency) factors. Some of the available biotechnological techniques applied for crop improvement are i) the genetic engineering, which allows the addition of foreign genes in the rice genome although being controversial due to the social and environmental concerns, ii) the anther culture, which fasten and improves the selection of new breeding lines, and iii) the Targeting Induced Local Lesions IN Genomes (TILLING) which combines the production of large mutant populations with the detection of mutants in genes of interest through molecular screening. The main aim of the thesis is to study different biotechnological tools and their applications to the improvement of Mediterranean rice varieties. To achieve this biotechnology is used to study the pollen dispersion of a genetically engineered rice line, to accelerate the stabilization process through anther culture technique and to introduce new variability using a mutagenesis protocol followed by molecular detection of mutants. In this thesis we first studied the pollen-mediated gene flow between wild rice, conventional rice and an herbicide resistant transgenic rice line in order to determine gene flow rates in relation to the distance and the prevailing wind speed and direction. Results showed that pollen dispersal is dramatically effected by the distances between rice plants and the speed and direction of the prevailing wind. Furthermore, the enhanced pollen dispersal capability of weedy rice can also play an important role in transgenic pollen dispersal, which unfortunately had been underestimated. Then, we adapted an anther culture protocol in order to efficiently obtain commercial dihaploid lines from a Mediterranean japonica variety. Furthermore, we described the greenhouse and field trials used to select the best lines for registration which are now being successfully commercialized. Finally, we developed a fast protocol for obtaining mutants with agronomic interest. This protocol is based on ethyl methanesulfonate mutagenesis of seed-derived calli. The in vitro regenerated mutant population plants were directly screened for senescence-related genes, allowing to shorten in more than eight months the common seed mutagenesis protocol. The molecular screening protocol was also optimized and several potential delayed senescence mutants were identified and tested.

In the breeding of grain sorghum (Sorghum bicolour L. Moench) towards improved nutrition and agronomic performance, new methodologies are required to increase genetic diversity and lower the inputs required to track and screen breeding populations. Near-infrared calibration models were developed by partial least squares (PLS) and test-set validation on 364 sorghum samples to predict crude protein and moisture content on whole-grain and milled flour samples. Models using milled flour spectra were more accurately predictive than those from whole grain spectra for all constituents (eg. Protein: R2 = 0.986 on flour vs R2 = 0.962 on whole grain). Discriminant calibrations were established to classify grain colour using partial least squares discriminant analysis (PLS-DA) based upon CIE L*a*b* reference values and visual ranking. Preliminary calibrations were developed for quantities of 18 amino acids, fat and apparent metabolisable energy (AME) on 40 samples using cross-validation, highlighting potential for reliable calibration for these parameters in sorghum. An investigation into the potential of 12C6+ heavy-ion beam mutagenesis of sorghum seed was undertaken by treatment at RIKEN Accelerator Research Facility (Saitama, Japan) and subsequent breeding at Ukulinga research farm and analysis at the Department of Plant Pathology, University of KwaZulu-Natal, Pietermaritzburg, South Africa. Dosage rates of 75, 100 and 150 Gy were compared in seven sorghum varieties to establish optimal dose treatments as determined by germination and survival rates, visible morphological changes and field data over two seasons of field trials. Crude protein variation within the M2 generation was analysed to compare dose rate effects. The need for higher dose rates was indicated by few quantified differences between treatments and control although good correlations between protein deviation and treatment dose rate were elucidated. Differences in varietal response suggest a need to optimize dose rate for specific varieties in future endeavours. In addition, all mutagenized populations were screened for crude protein content using near-infrared spectroscopy (NIRS). Significant differences in protein levels and standard deviations were observed between treated self-pollinated M2 generations and untreated control populations. Individual plants displaying significantly different protein levels were isolated.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Cowpea yields in Mozambique can be increased through breeding farmers’ accepted cultivars with drought tolerance and stability across environments. A study was conducted in the southern region of Mozambique to: (1) determine farmers perceptions on major constraints limiting cowpea production and identify preferences regarding cultivars and traits, (2) determine the variability of selected cowpea germplasm for drought tolerance, (3) determine the gene action controlling drought tolerance, yield and yield components in cowpea, and (4) assess the genotype × environment interaction and yield stability of cowpea genotypes under drought-stressed and non-stressed conditions. The study on farmers’ perceptions about the major constraints limiting cowpea production and preferences regarding cowpea cultivars and traits established that cowpea was an important crop, cultivated for its grain, leaves and fresh pods for household consumption and the market. The study revealed that cowpea grain and leaves were equally important across the three districts in the study. Differences in accessibility to markets between districts influenced the ranking of grain and leaves among districts. Grain was more important in Bilene and Chibuto districts which are situated far from the major urban centre, Maputo, while leaves were more important in Boane district which is near the major market of Maputo. Fresh pods were important in Bilene district which is situated along the major highway connecting Maputo and other provinces. Drought was the most important production constraint followed by aphids, bruchids and viral diseases. The criteria used by farmers to select cowpea varieties included high grain and leaf yield, large seed size, earliness, smoothness of the testa and potential marketability of the variety. The implication of this study is that different types of varieties need to be developed for different areas. Dual-purpose or grain-type varieties need to be developed for areas situated far away from the major markets while varieties for leaf production need to be bred for areas near major markets. During the breeding process, a selection index needs to be adopted whereby drought tolerance, high grain and leaf yield, large seed size, smooth testa, earliness, aphids and bruchids resistance should be integrated as components of the index. High grain yield should receive high weight for varieties developed for areas located far from major markets while high leaf yield would receive high weight for varieties developed for areas located near major markets. The study on variability of cowpea germplasm collections for drought tolerance revealed wide genotypic variability among the tested germplasm. Biplot displays indicated that the genotypes could be grouped into four categories according to their drought tolerance and yielding ability as indicated below: high yielding-drought tolerant (group A), high yielding-drought susceptible (group B), low yielding-drought tolerant (group C), and low yielding-drought susceptible (group D). Examples of high yielding-drought tolerant genotypes were Sh-50, UC-524B, INIA-24, INIA-120, IT96D-610 and Tete-2. Stress tolerance index was the best criterion for assessing genotypes for variability in drought tolerance because it enabled the identification of high yielding and drought tolerant genotypes (group A). The assessment on gene action controlling drought tolerance (stay-green), yield and components indicated that both additive and non-additive effects were involved in controlling all of these traits. Additive gene action was more important than non-additive gene affects in controlling stay-green, days to flowering, number of pods per plant, number of seeds per pod and hundred seed weight. Under no-stress conditions, additive gene action was more important than non-additive gene action while under drought-stressed conditions, non-additive gene effects were more important than additive gene effects. Stay-green can easily be assessed visually in early segregating populations while yield and yield related traits cannot. Hence, selection for drought tolerance using the stay-green trait would be effective in early segregating generations while selection for yield and number of pods per plant would be effective in late segregating generations. Selection for yield could be conducted directly under no-stress conditions and indirectly using the number of pods per plant under drought stress conditions. Genotype INIA-41 would be the most desirable to use as a parent for drought tolerance and IT93K-503-1 would be the most desirable to use as a parent for drought tolerance and yield. The assessment on genotype × environment interaction and cowpea grain yield stability for forty-eight (48) cowpea genotypes grown under drought-stressed and non-stressed conditions indicated that cross-over genotype × environment interactions were present for yield indicating that genotypes responded differently to varying environmental conditions. Genotypes adapted to specific environmental conditions could be identified. Genotypes IT-18, INIA-51, INIA-51A and Nhavanca were adapted to non-stressed environments that were either drought stressed or non-stressed while VAR-11D was adapted to low yielding, stressful environments. Genotypes INIA-23A, INIA-81D, INIA-24, INIA-25, INIA-16 and INIA-76 were high yielding and stable while genotypes IT-18, INIA-51, INIA-51A, Nhavanca and VAR-11D were high yielding and unstable. Genotypes Bambey-21, INIA-36, INIA-12 and Monteiro were consistently low yielding and stable except INIA-12 that was consistently unstable. Chókwè was a high yielding environment and suitable for identifying high yielding genotypes but not ideal for selection because it was not representative of an average environment while Umbeluzi was low yielding and not ideal for selection. Overall, the study revealed that genetic improvement of drought tolerance and yield would be feasible. Potential parents for genetic improvement for yield and drought tolerance were identified. However, further studies for assessing yield stability of cowpea genotypes are necessary and could be achieved by including more seasons and sites to get a better understanding of the genotype × environment interaction and yield stability of cowpea in Mozambique.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

碩士
國立屏東科技大學
熱帶農業暨國際合作系
104
Domesticated chili peppers (capsicum spp) have been developed by breeders through crosses and produce abundant varieties. This study aimed to investigate the growth characters and contents of capsaicinoid in different collected lines of chili pepper capsicum. Their F1 crosses sets were also investigated. The genetic variance on heritability of agronomic traits and pungency will be determined. In first experiment; we conducted morphological character identification from six commercial varieties. Estimation of broad sense heritability on all character suggested that fruit width (h2=0.195) and seed length (h2 = 0.179) were potentially better breeding indexes. Hybridization crosses between “Chicken heart green and Indian ghost” varieties based on their distinct agronomic traits was also carried out. We collected successful five F1 replicates and investigated their pollen fertility and yield potential on each summer and winter. Results from F1 replicates showed best months to do hybridization in (NPUST) Taiwan, is in June and July during summer season. Secondly, we conducted morphological character identification from four AVRDC lines. The results of estimation of broad sense heritability showed that fruit weight per plant (h2=0.332) and days of fruiting (h2=0.983) were potentially better in breeding indexes as well. Third, we identified all tested materials on their pollen viability under in vitro germination. The results showed that the best time for collect viable pollen is at 9 to 11 am during sunny day. For final experiment we performed a reciprocal diallel crosses to all commercial chili pepper capsicum, based on their genetic variations to identify their F1 correlation to the parents on all characters together with capsaicin contents. The results showed that within diallel cross between “Chicken heart green” and “Devil scorpion” had highest successful fruit set (28.3%) and two varieties that showed best fruit set in reciprocal are “chicken heart green” and “chicken heart yellow”. Diallel to conduct correlation and heritability were 20 quantitative. The results of estimation of broad sense heritability showed that days of fruiting (h2=0.305) followed by fruit weight (h2=0.195) were best traits to consider on selection. Part of F1 performances, showed lower than parents (27-54 cm) in plant height (17-24 cm) and higher in fruit height (3.1 – 4 cm) better than parents (2-3 cm). F1 showed earlier than parents in matured day (54 ) which parent matured day (60-61).The result capsaicin analysis showed that F1 of “Chicken heart green” cross between “Indian ghost” (14,805.61ppm) and F1 of “Chicken heart green” cross between “Chicken heart yellow” (3,793) indicated the potential as a good source of food, income, good breeding material and bio control for pest. Therefore, all selection results could be based on traits that adapted to (NPUST) Taiwan environment among (commercial lines, AVRDC lines and diallel including pollen test viability. Potentially, breeder should obtain, observed and understand the plants genes and environment in order to do better selection.

碩士
國立中興大學
農藝學系所
105
Straw is a by-product of rice after harvest, it is majorly consisted of lignocelluloses and is difficult to be degraded in the soil. The brittle culm mutants have mutation related with decreased secondary cell wall thickness and maybe easier for degradation. IR64 and TNG67 mutation pools were developed by sodium azide in our previous breeding programs. There were 21 and 23 brittle mutant lines selected from IR64 and TNG67 mutant pools. The brittle lines have differences in brittleness score from 0 to 5. IRB3 is a brittle culm mutant of IR64, it showed a Score 3 brittleness and easily to fracture by finger-bending. Bacterial blight disease is an important disease in rice, IRB3 was crossed with TN11/IRBB66 BC2F4 harboring with four bacterial blight resistant genes (xa5/Xa7/xa13/Xa21) to breed a variety with both blight resistance and brittle culm. In marker-assisted selection, the simple sequence repeat (SSR) markers linked to four Xa genes were applied in the breeding program. In phenotyping selection, plants were inoculated with Xoo-F2 and XF89-b strains by leaf-clipping method and investigated the disease lesion on leaves. The brittleness of IRB3 was controlled by a single recessive gene (non-brittle: brittle; 3: 1; χ2 = 0.223). The brittle gene of IRB3 was mapped on the chromosome 10 in a region of 666 kb between RM271 and RM5392 markers using a F2 population of IRB3 cross TN11/IRBB66 BC2F4. Using bioinformatics, seven candidate genes including the OsCesA7, which relates to the cellulose synthesis may control the brittle culm trait. Further study will be conducted to identify the gene responsible for the brittleness and to develop the functional marker for MAS to introduce the brittleness trait through MAS.

In South Africa, a shortage of litchi cultivars to expand the very short harvesting period has seriously threatened the viability of the local export orientated Litchi Industry. Only two cultivars have dominated commercial plantings for more than a century, namely ‘HLH Mauritius’ and ‘McLean’s Red’. The marketing period of litchis from South Africa coincides with large export volumes from competitor countries such as Madagascar, resulting in lower returns for local growers. To address this situation, the late season cultivar ‘Wai Chee’ was imported amongst others from Australia. ‘Wai Chee’ is harvested at a time in South Africa when there is a gap in worldwide litchi production, making the cultivar potentially very profitable. However, its potential and subsequent use in the industry is affected by small fruit size and questionable internal quality. As the South African Litchi Industry is export orientated and the qualities of ‘HLH Mauritius’ fruit currently dictate export requirements, solutions need to be found to improve fruit size and fruit quality in ‘Wai Chee’ litchi. In this study, a number of horticultural manipulation techniques were investigated with the aim of enhancing yield, fruit size and quality in ‘Wai Chee’ litchi. The use of chemical applications of foliar nutrients and plant growth regulators were found to improve certain fruit characteristics in ‘Wai Chee’. Foliar nutrient applications of nitrogen, potassium and calcium during the early stages of fruit set and -development improved fruit set and subsequently yield, and also increased fruit mass, fruit size and flesh mass. Treatments with potassium nitrate (KNOз), calcium nitrate (CaNOз) and calcium metalosate proved to be the most enhancing nutrient applications. Applications of synthetic auxins and auxin-like substances during the 2-3g stage of fruit development improved fruit size, fruit mass and flesh mass in ‘Wai Chee’. The combination treatment of Tipimon® (2,4,5-TP), applied at the 2-3g stage, followed by Maxim® (3,5,6-TPA) a week later, yielded the best results in this regard. With biological practices, pollination was found to have an influence on litchi tree- and fruit characteristics. Pollen source proved to have an influence on fruit set and fruit retention at harvest in ‘Wai Chee’. Initial fruit set was lower when using cross-pollination compared to the use of self-pollination in female flowers of ‘Wai Chee’, whereas final fruit retention was higher with the use of cross-pollinators when compared to retention of fruit with self-pollination. Although some beneficial effects with different pollen donors on fruit characteristics were observed, these effects were not significant, and would therefore necessitate further investigation. Pollen donor effect on quality parameters such as Titratable acid (TA)- and Total Soluble Solid (TSS) content of fruit was not significant. Cultivar differences regarding fruit characteristics and maturation rate were detected with the use of cultural practices such as bunch covering materials in ‘HLH Mauritius’ and ‘Wai Chee’. Beneficial effects on fruit size were obtained with thicker covering materials with nominal mass of 70 and 80 g/m² respectively on ‘HLH Mauritius’, while with ‘Wai Chee’, thinner covering materials (60 and 65 g/m²) showed enhancing effects. Maturation rate was significantly delayed only on ‘Wai Chee’ with the use of thicker covering materials (70 and 80 g/m²). Differences in colour were detected amongst different covering materials, but these should be verified with chromameter technology. Covering of fruit bunches for better fruit size and a later harvest date would, especially for ‘Wai Chee’ as a late season cultivar, be beneficial, since better prices are realised towards the end of the season.
Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.