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.

Rice (Oryza sativa L.) is the second most important cereal crop in Malawi. Rice productivity in the dominant (85%) rainfed ecosystem is very low, with mean yield of only 1.4 t ha-1. Farmers plant traditional landraces that have low yield potential and are susceptible to various stresses such as drought and diseases. Development and introduction of improved rice varieties, with stress tolerance traits from introduced varieties, such as the New Rice for Africa (NERICAs), could significantly increase productivity. Previous attempts to introduce high yielding irrigated varieties into the dominant rainfed ecosystem in Malawi have not been successful because farmers basically did not adopt the varieties, claiming that the varieties were lacking in grain traits that they preferred but that the traits were present in their landraces. The notable traits mentioned, through previous informal surveys, were long grains, medium to slender shape and aromatic grain with intermediate gelatinization temperature. No formal study has been conducted to ascertain the preferences, and the genetic control of the traits, including yield and yield related traits, have not been studied. The objectives of this study were to: 1) confirm farmers’ preferences for grain traits using participatory rural appraisal; 2) determine amount of genetic variability for yield and yield related traits in Malawi rice landraces, 3) determine the genetic control and correlations of grain length, grain shape and 1000-grain weight, 4) determine the inheritance of aroma and gelatinization temperature and, 5) determine the genetic control, correlations and path coefficients of yield and yield related traits, in F2 generations of Malawi rice landraces and NERICA varieties crosses. To confirm the farmers’ preferences for grain traits, a participatory rural appraisal was conducted in 2006 in two villages that were representative of rainfed rice growing areas in Malawi. The villages were Liundi and Nawanga in Machinga and Salima Districts, respectively. Qualitative and quantitative data were collected through questionnaires and discussions with 190 respondents, as well as through observations. To determine variability among Malawi rice landraces, 19 landraces were planted at Lifuwu in a Randomized Complete Block Design with three replicates in 2006. Data on plant height, days to 50% flowering, number of panicles per hill, panicle length, number of filled grains per panicle, 1000-grain weight, panicle weight, grain length and grain yield were collected and analyzed. Four Malawi rice landraces were crossed to four NERICA varieties in 2006 in a North Carolina Design II mating scheme to determine the genetic control of grain size. F1 plants were raised in 2007 and in 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Data on grain length, grain shape and 1000-grain weight were collected and analyzed. To determine the inheritance of aroma and gelatinization temperature, four Malawi rice landraces were crossed to four NERICA varieties in 2006 and F1 plants were raised in 2007. In 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Aroma and gelatinization temperature were evaluated. To determine the gene action of yield and yield related traits, four Malawi rice landraces were crossed to four NERICA varieties in 2006 in a North Carolina Design II mating scheme and F1 plants were raised in 2007. In 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Data on grain yield, the number of panicles per hill, days to 50% flowering, panicle length, panicle weight and 1000-grain weight were collected and analyzed The participatory rural appraisal confirmed that that long, slender or medium shape grains, with aroma and intermediate gelatinization temperature were the key traits preferred by farmers. Therefore the farmer preferred traits of long, slender grains, with aroma and medium gelatinization temperature, must be selected for in any high yielding varieties to be developed for the rainfed rice ecosystem. Results showed that differences were significant (P=0.05) for all the traits that were studied. Heritability estimates were low to moderate: 18.3% for panicle weight, 40.0% for panicles per hill and 56.3% for days to 50% flowering date. The high genetic variability among the landraces could be used in a breeding programme to develop improved varieties for various morphological traits. The number of panicles per hill and 1000-grain weight combined moderate heritabilities with relatively high genetic advance and therefore could be reliable traits for yield improvement. Genetic analysis of grain size showed that Malawi rice landraces were variable for all three grain size characteristics, namely grain length, grain shape and 1000-grain weight. NERICA varieties were variable for 1000-grain weight. Sixteen F2 progenies were variable for all three characteristics, and the variability was significant (P=0.05). Heritability estimates were high (45.4%) for grain length and low for grain shape (12.3%) and for 1000-grain weight (14.3%) suggesting that early generation selection would be effective for grain length. Predominance of additive gene action for grain length and grain shape suggested that early generation selection would be effective for these traits. Selection for 1000-grain weight would be more effective in later generations because of preponderance of non-additive gene action in the control of this trait. The correlation between grain length and grain shape was positive (r=0.769) and highly significant (P=0.01) suggesting that breeders would choose to select for both traits simultaneously, or they would choose one of the traits to develop varieties with long grains and medium shape. Crosses between aromatic and non-aromatic varieties had non-aromatic F1. The F2 progenies segregated into 3:1 ratio for non-aromatic: aromatic suggesting that, in the Malawi rice landraces, aroma was probably simply inherited through a single recessive gene. F1 progenies, between parents with high and intermediate gelatinization temperatures had intermediate gelatinization temperature. F2 progenies segregated into 1:3 ratios for high; intermediate gelatinization temperature in three out of four crosses suggesting control by one dominant gene. The segregation pattern in one cross was not significantly different from 3:13 ratio for high: intermediate suggesting that two dominant genes, one an inhibitor, were controlling the trait. Breeding and selecting for aroma and intermediate gelatinization temperature could be accomplished relatively easily because the traits are simply inherited. The genetic variability for yield and yield related traits was wide and significant (P=0.05) in the F2 populations of Malawi rice landraces and NERICA varieties crosses indicating that the populations would be valuable sources to develop varieties with improved yield. Panicle weight and the number of panicles per hill were positively correlated with, and had high direct effects on grain yield, therefore they could be used to indirectly select for high yield. Grain yield, the number of panicles per hill and plant height were predominantly controlled by additive gene action suggesting that bulk breeding methods would be adopted for these traits. The days to 50% flowering, panicle weight and 1000-grain weight were predominantly under the control of nonadditive gene action suggesting that hybrid development would be profitable for these traits. Faya Mpata, Faya Zidyana and NERICA 3 could be the best parents for improving yield and yield related traits because they had high general combining abilities for the traits. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

This study compared DNA based SSR markers with total seed protein markers, used to evaluate genetic diversity of sunflower. The multiplex-ability, cost effectiveness and applicability of microsatellites as molecular markers for a genetic diversity study were investigated and evaluated based on pedigree data of the sunflower germplasm. A solution for oil and fat interference in ultrathin iso-electric focusing gels was investigated, in order to make imaging and interpretation easier and clearer. Total protein analysis was utilized for the determination of genetic diversity on the same inbred material used for the DNA analysis. Finally a correlation is made between the data obtained on DNA vs Protein compared with phenotype and expected pedigree data. A set of 73 SSR markers with known mapped positions were utilized to determine genetic similarity in a group of sunflower inbred lines. Cluster analysis of genetic similarity revealed an excellent correlation with the breeding background and source information obtained from breeders on all inbred lines used in this study. Cluster analysis gave a clear differentiation between B and R-lines, showing clearly defined heterotic groups of the proprietary set of inbred lines. The most outstanding single-locus SSR markers in the set used for this study were identified and used as a core set. Multiplex assays were designed and optimized for the most cost and time effective method for rapid variety identification. The selected markers produced robust PCR products, amplified a single locus each, were polymorphic among the elite inbred lines and supplied a good, genome-wide framework of completely co-dominant, single-locus DNA markers for molecular breeding. The use of a fluorescent-tailed primer technique resulted in a considerable cost saving. Furthermore, the SSR markers can be multiplexed through optimization, in order to avoid undesirable primer-primer interactions and non-specific amplification. First stage iso-electric focusing of total protein extracts were used to analyze sunflower looking at genetic purity and genetic variety verification on diverse sunflower germplasm. Severe visual interference was visible on most seed storage protein extracts of sunflower. This interference was visible as a distortion in the gel matrix on the anodal end of the gel, and caused important proteins to denature in the presence of heightened field strength and the absence of a uniform matrix. Adjustment of the extraction solutions removed this interference. Total protein profiles were generated with the use ultrathin layer iso-electric focusing (UTLIEF) to assess the level of genetic diversity on the same set of sunflower lines used for the SSR analysis. Finally, the genetic diversity of the sunflower germplasm was analysed by comparing proteomic, genomic and pedigree data from the same germplasm. A total of 295 alleles were amplified with a set of 73 SSR markers with known mapped positions. These were utilized to determine the genetic relatedness of a group of B-lines and R-lines of sunflower. In parallel, a total of 68 protein bands were visualized using protein samples of two types of seed storage proteins derived from exactly the same sunflower lines. Cluster analysis clearly differentiated between the B-lines and R-lines, identifying defined heterotic groups of this proprietary set of lines. The comparison of DNA and protein data for the application of genetic diversity studies is analysed, as well as the general comparison on the use of the two different molecules as markers. / Thesis (Ph.D)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Despite the increasing number of farmers growing cassava in Zambia, yield per hectare has remained low at 5.8 t ha-1. The major constraints contributing to low yields are pests and diseases of which cassava mosaic disease (CMD) caused by East Africa cassava mosaic virus (EACMV), Africa cassava mosaic virus (ACMV) and South Africa mosaic virus (SACMV) is the most important. Breeding of cassava is restricted by limited information on viruses and associated satellites, and farmer preferences. Most of the farmers cannot manage to institute control strategies that require buying of chemicals. The most feasible option remains improving existing cultivars through resistance breeding. The study therefore was conducted to: i) establish farmers’ perception and knowledge of CMD; ii) to identify viruses of cassava occurring in Luapula province; iii) evaluate the performance of local and improved cultivars for agronomic traits; iv) evaluate the performance of F1 progenies for CMD resistance; and v) determine general combining ability and specific combining ability for CMD resistance. The studies were carried out between 2008 and 2011 at different locations in Zambia. The information generated was important in formulating a local breeding strategy for CMD resistance. A participatory rural appraisal and a structured survey was conducted in Mansa, Samfya and Mwense districts in Luapula province involving farmers to ascertain farmers’ perceptions of CMD. The results of the study showed that the majority of the respondents (97.6%) were not aware of CMD. Most of the farmers grew landraces on small pieces of land. Although, the cultivars (local and improved) were widely grown, they were susceptible to CMD. The farmers preferred cultivars with high yielding and early bulking characteristics among others. A CMD survey conducted between April and May 2009 in Samfya, Mansa, Mwense, Kawambwa and Nchelenge districts in Luapula province established East Africa cassava mosaic virus (EACMV), and Africa cassava mosaic virus (ACMV) as the most prominent viruses in the area. Symptoms of satellites were also observed in the farmers’ fields in most of the areas visited. Satellite II and III were detected in leaf samples. The CMD incidence (59.1%) and severity (2.4) was moderate across the districts surveyed. The CMD symptoms on the cassava plants were variable with plants showing mild and severe symptoms characterised with narrowing and reduced leaf blades. The transmission of CMD infections was mainly through cuttings rather than via whitefly infection which means that most of the planting materials used by the farmers were infected. Evaluation of cassava cultivars for CMD resistance was conducted in 2009/2010 and 2010/11 seasons at Mansa Research Station in Luapula province using a 4 x 4 α lattice design. Both introduced and locally grown cultivars had significant (P<0.001) differences in their reaction to CMD. Bangweulu, Namuyongo, Kalaba, Chikula, Mwakamoya, Chila7 and Chila11 were the most susceptible genotypes. Mweru, Tanganyika, and Nalumino were moderately tolerant to CMD. Eight hundred F1 genotypes developed using a North Carolina II mating design were evaluated in a 4 x 5 α lattice design in 2011 at Mansa Research Station, Luapula province to determine combining ability for reaction to CMD, yield and yield components. The plants were harvested 7 months after planting (MAP). Significant (P<0.001) general combining ability and specific general combining ability were recorded for CMD. The SCA effects were more important for CMD than GCA effects suggesting that non-additive gene action was more prominent than the additive gene action in determining CMD reaction. Parent lines with desired significant, negative GCA effects for reaction to CMD were Bangweulu, Kampolombo, Nalumino and TME2. In general, the survey and participatory rural appraisal established CMD as one of the constraints to cassava production and created a basis for the research study. The findings indicate opportunities that exist in creating genotypes with tolerance to CMD. The study identified cassava lines with resistance to CMD. The lines that expressed the above trait should be selected and tested further for release to the farmers in Zambia. Since the clonal evaluation trial was harvested at 7 MAP, there is need to investigate further for earliness trait in best performing lines in different locations. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Participation of farmers in plant breeding programmes has been reported to increase breeding efficiency. Farmers’ participation bridges the gap between variety development and dissemination and provides an opportunity for farmers to select varieties they prefer. The breeders on the others hand learn more about the farmers’ preferences and the environment in which the new varieties will be grown. However, the advantages of participatory breeding can best be realized when farmers’ indigenous technical knowledge (ITK) and experience complement the breeder’s scientific knowledge and skills. Cassava (Manihot esculenta Crantz) is a clonally propagated crop grown in diverse environments by small scale farmers for subsistence. Information on the roles of farmers and breeders at various stages of breeding and their ability to effectively participate in breeding programmes is limited. The objectives of this study were to determine: (1) cassava farmers’ preferences, production constraints and systems; (2) farmers’ selection criteria of cassava varieties; (3) genetic inheritance of farmer preferred traits; (4) how farmers and breeders complement each other at all stages and activities of cassava breeding. Participatory rural appraisal was conducted in three purposefully sampled districts of western Kenya based on ethnicity and agro-ecology. The results reveal that cassava is predominantly grown by small scale farmers with mean land size of 1.6 ha mainly under mixed cropping system for subsistence. The storage roots are eaten either after boiling or processing to flour. The majority of farmers (over 60%) are aware of the improved varieties but adoption rate is low (18% in some districts). The effects of pests and diseases, and the lack of high yielding varieties, capital, land, and disease free planting material are the most important constraints to cassava production. Farmers prefer tall, high yielding varieties that are resistant to diseases and pests, early maturing and long underground storability of harvestable storage roots. The districts surveyed significantly differed in popularity of utilization methods, traits preferences and relative ranking of the production constraints indicative of differences in ethnicity and agro-ecology. Three farmer groups from the three districts selected in western Kenya were used to study farmers’ variety selection criteria based on their own indigenous technical knowledge (ITK). The groups evaluated 15 (10 landraces and five improved) popular cassava varieties with concealed identities on their farms. The results revealed that farmers have effective methods of selecting varieties for most of their preferred traits. However, ITK alone cannot be used to evaluate all the important traits, such as cyanide content. The genetic inheritance of farmer preferred traits was determined through a genetic study. Six landraces and four improved varieties popular in western Kenya were crossed using the North Carolina mating design II to generate 24 full-sib families. The 24 families, represented by 40 siblings each, were evaluated at two sites, Kakamega and Alupe research station farms, in a 24 x 40 a-lattice design. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P<0.05) for all traits evaluated except dry matter content and cyanide content. However, non-additive gene action predominated over additive gene for cassava mosaic disease (CMD) resistance, height to first branching, total number of storage roots per plant and fresh storage root yield in all environments. The best crosses were not necessarily obtained from parents with high general combining ability confirming the presence of non-additive gene action. The best performing parents per se did not necessarily have high GCA effects implying that selection based on the per se performance of parents may not always lead to development of superior hybrids. The clonal evaluation trial (CET) was established at Alupe research station and evaluated by the breeder and farmers from two districts independently. Three selection criteria were tested to determine the most appropriate approach to selection of varieties that meet both farmers’ and breeder’s preferences. The selection criteria were; farmers’ independent selection index (SI) derived from farmers’ selection criteria from each district, breeder’s negative selection and independent SI, and a participatory SI which combines farmers’ and breeder’s selection criteria. There was 14% overlap among the top 100 varieties selected by farmers from all districts and the breeder when independent SI were used. However, there was 49% overlap among the top 100 varieties selected by farmers using participatory SI and the breeder’s SI. The farmers and the breeder have a role to play in the variety development process. Varieties with traits preferred by both the farmers and the breeder are likely to enhance breeding efficiency and effectiveness. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Soybean is emerging as a very important food, market and oil crop in Ethiopia. However, its productivity in Western Ethiopia is constrained by several production constraints, of which soil acidity is one of the most important ones. On acidic soils the availability of several plant nutrients is limited; among which phosphorus is the least available. Thus, development of high yielding and low P tolerant soybean varieties need to be among the top priorities in areas with such problematic soils. Therefore, the objectives of the study were to: 1) conduct a Participatory Rural Appraisal (PRA) study to assess farmers’ perception on various soil fertility, soybean consumption and marketing issues, 2) evaluate soybean genotypes under low and high P regimes, and 3) conduct genetic analysis of soybean performance under low and high P conditions. The PRA was conducted to assess farmers’ perception on various soil fertility, soybean consumptions and market issues. A total of 186 soybean producing farmers across three locations of Western Ethiopia were interviewed using a semi-structured questionnaire. Results from the study indicated that the use of soybean for crop rotation and soil fertility improvement was more important to the farmers than household consumption and marketing of the crop. The study also revealed poor demand for soybean compared to other crops on the local market. The majority of respondent farmers’ recognized that soil fertility has been declining over time and obtaining inorganic fertilizers on time was difficult; mainly due to high price of fertilizer. Though farmers’ cooperative was identified as the major supplier of fertilizer, farmers rated the quality of its service in supplying fertilizer as poor. With deteriorating soil fertility and limited capacity to use inorganic fertilizers, farmers are producing soybean under low soil fertility conditions. Thus, breeding programs need to develop varieties that perform well under low fertility soil. Screening soybean genotypes for response to different P regimes was performed in a field experiment using a split plot design, where the main plots were three levels of applied P (0, 100 and 200 kg ha-1 P), and the sub plots were 36 soybean genotypes (G) planted across three locations (L) with two replications. The extent of genetic variation of the 36 soybean genotypes was assessed under low (0 kg ha-1) and high P (100 kg ha-1) conditions. The analysis of variance revealed significant differences among genotypes for all the traits, except pod number at low P; while all the traits, except root volume, pod number, and number of seeds per pod showed significant differences at high P. Plant fresh weight, root fresh weight and root volume exhibited high genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) under both P conditions. Both principal component and cluster analyses revealed variation in the population. The 100-seed weight, plant height, roots and plant fresh weight combined high heritability and genetic advance estimates indicating that the inheritance of such traits is controlled by additive gene action under both P conditions. In general, the study revealed high genetic variation in the population, which can be exploited to improve performance under both high and low P conditions. The analysis of variance revealed significant genotype X phosphorus (GXP) interaction for number of nodules and total nodule weight at Jimma, and Assossa, and for root weight and root volume at Mettu. Though the GXP and GXPXL interactions showed non-significant difference for across locations analysis, the genotypes displayed significant difference for root fresh weight, root volume, tap root length, and weight of effective nodule. Genotypes: Pr-142 (26), AGS-3-1, SCS-1, AGS 234, and H 3 were identified among the best for root and nodulation characteristics. Yield and yield related traits were also assessed separately in the screening program. The results revealed significant GXP interactions for grain yield only at one site; while the genotypes exhibited highly significant differences for most of the traits in all the sites. G and GXL interaction were significantly different for most the traits. Essex 1, IAC 11, and AGS-3-1 were the best performing genotypes at high P; while genotypes IAC 11, AA 7138, G 9945 and AGS-7-1 displayed tolerance to low P. Genotypes AA-7138, PR-142 (26) and H3 exhibited stable performance across the three P levels. These genotypes have paramount significance in breeding soybean for low P tolerance and stable performance in varying P conditions for resource poor subsistence farmers.The genetic control mechanism for the major quantitative traits for performance under high and low P condition was studied in a nine parent half diallel cross. The results revealed that the GCA effects were highly significant for grain yield, pod length, days to maturity and plant height under low-P conditions. GCA effects were highly significant for grain yield, 100-seed weight, days to maturity, plant height, pod number, and pod length under high P. GCA effects were also significant for number of seeds per pod under high P condition. In addition, the relative contribution of GCA was higher than SCA under both P conditions, except for 100-seed weight at low P. Variety Hardee-1 was the best general combiner for most of the quantitative traits under both P conditions, indicating that it can be used in breeding programs to improve soybean for better genetic response to low and high P. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Groundnut (Arachis hypogaea L.) is an important food and cash crop in Mozambique and production has been constrained by lack of high-yielding cultivars and disease infection. Objectives of this study were: 1) to identify farmers’ major groundnut production constraints and their preferences for cultivars; 2) to determine genotypic variation among landraces for agro-morphological traits and resistance to groundnut rosette disease; 3) to determine agronomic performance and resistance to groundnut rosette disease among advanced groundnut lines; and 4) to determine the inheritance of resistance to groundnut rosette disease. The study was conducted in northern Mozambique from 2008/2009 to 2010/2011. In attempt to identify farmers’ major groundnut production constraints and their preferences in cultivars, a participatory rural appraisal (PRA) was conducted in Namuno and Erati districts in northern Mozambique. Results from the PRA showed that farmers were aware of the constraints affecting groundnut production and productivity in the study area. The major constraints included groundnut rosette disease, insect pests, lack of seeds and improved cultivars, low soil fertility and lack of infra-structure. Groundnut rosette disease was ranked the most important constraint, and it was widespread in the region. Selection criterion for groundnut cultivars used by women differed from that used by men within village and across villages. However, high yield and oil content were the most important traits preferred by farmers followed by pod and seed size, earliness, disease and insect pest resistance. Fifty-eight groundnut landraces were collected from northern Mozambique (Nampula, Cabo Delgado, Niassa and Zambezia) and evaluated for variation in agro-morphological traits and resistance to groundnut rosette disease. The landraces showed high phenotypic diversity in agro-morphological traits. Clustering by nearest neighbour method indicated that the genotypes could be grouped into six clusters, indicating that agro-morphological diversity exists. The highest yielding genotypes were Pambara-4, Pambara-2, Pambara-6, lle-1, Imponge-1-Tom and Gile-5. There was considerable genetic variability for resistance to groundnut rosette disease among the landraces. Four landraces (PAN-4, Imponge-4, Pambara-3, Metarica Joao) were classified as resistant. No significant correlation was observed between seed yield and groundnut rosette incidence. Thirty-two improved lines were evaluated for performance in two growing seasons across three locations in northern Mozambique (Nampula, Namapa and Mapupulo). The results indicated that the highest yielding genotype was 23A and the highest yielding location was Namapa. There was a significant and negative correlation between seed yield and groundnut rosette disease indicating that the seed yield was negatively influenced by the disease. The results on stability analysis indicated that genotype 35B was the most stable across environments since it had coefficient of regression around unity (bi=1.024), high coefficient of determination (R2=0.999), and small variance deviation (var-dev=162.8), and 13 % above average seed yield. It is, therefore, concluded that genotype 35A could be recommended for cultivation on diverse environments of northern Mozambique. A trial was conducted using the parents and F2 populations derived from a 7 X 7 diallel cross. The test materials were infected with groundnut rosette disease using the spreader-row technique. The results indicated that no genotype was immune to disease. The mean squares due to both general combining ability (GCA) and specific combining ability (SCA) were significant indicating that additive and non-additive gene actions were involved in the expression of resistance to groundnut rosette disease. The general predictability ratio (GCA:SCA) was 0.97, indicating the predominance of additive over non-additive gene action in the inheritance of the disease. The study also found that groundnut rosette disease was controlled by two recessive genes. However, some genetic modifiers may also be present and influence disease expression. In general, the study revealed that breeding opportunities do exist, incorporating farmers preferred traits and major groundnut production constraints into new groundnut cultivars. Improving cultivars for resistance to groundnut rosette disease will be a major breeding focus, while selection for other traits and constraints will not be ignored. Resistance has been identified from local landraces. Advanced lines with high yields across environments were identified that can be recommended for release. The high significant additive effects observed for groundnut rosette disease implied genetic advance could be effective in the F2 and later generations through selection, although modifiers could slow the progress. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Sorghum [Sorghum bicolor (L.) Moench] is one of the most important cereal crops grown in arid and semi-arid regions of the world. The North Eastern regions of Ethiopia are known for its high sorghum production and genetic diversity, and proneness to moisture stress. Globally, moisture stress is one of the major sorghum production constraints limiting genetic gain through breeding. Although, the importance of Ethiopia’s sorghum germpalsm has been widely recognized both nationally and internationally, the genetic potential of the germplasm has not yet been fully assessed and exploited in breeding programmes. Therefore, the objectives of this study were: (1) to evaluate sorghum production systems and patterns, major production constraints and cropping mechanisms, varietal diversification, farmers’ criteria for choosing varieties over time and space, and adoption of improved varieties, (2) to assess the agro-morphological and molecular diversity and population structure of lowland sorghum landraces collected from different geographic origins using morphological and SSR markers, (3) to assess the performance of sorghum landraces under moisture stress conditions and identify promising lines, and (4) to determine heterosis and combining ability of lowland sorghum landraces for grain yield, yield components and drought tolerance and to identify suitable parents for future hybrid cultivar development for the North Eastern Ethiopia or similar environments. A survey was conducted in the North Eastern Ethiopia sampling three Administrative Zones, six Districts and 12 Peasant Associations. Data was gathered from a total of 171 farmers and analyzed using SPSS statistical package. The results suggest that the performance of sorghum was generally poor mainly due to moisture stress, pests, diseases, weeds, farmland fragmentation due to demographic pressure, poor soil fertility, and poor performance of the local varieties. The productivity of sorghum was also largely hindered by the use of inherently poor yielding local landraces as farmers were forced to abandon their high yielding, big-headed and late maturing sorghum varieties due to the prevalence of recurrent moisture stress. The survey found that the region is as a rich source of genetic diversity and more than 70 distinct sorghum landraces were identified. The majority of the farmers grew their local landraces, despite the accessibility and availability of many improved sorghum varieties and production packages. Farmers were willing to adopt the improved varieties if they had farmers preferred attributes such as as red seed colour, tall with high biomass yield. To benefit the most from the available improved technologies, farmers have to be part of the breeding process right from the very beginning. Lowland sorghum accessions which exhibited farmer-desired traits were selected from the entire landrace germplasm collection at the national gene bank of Ethiopia. Field evaluations of the selected 278 landraces together with checks were held at Sirinka and Kobo agricultural research stations for 12 qualitative and 10 quantitative traits under stress and non-stress conditions. Two hundrad landraces were selected on the basis of their morphological distinctiveness and drought tolerance, in terms of earliness and yield stability. Molecular level diversity assessment was conducted using 30 SSR markers. Considerable magnitude of variation was observed among landraces between and within geographic origin for most of the traits studied. The morphological variability was also complemented by high molecular markers diversity. Thirty two pure lines were selected for inclusion as parents in the sorghum breeding programme for yield and drought tolerance. The selected lines were then crossed to four cytoplasmic male-sterile lines that had different cytoplasm systems (A1 to A4) using a line x tester mating design scheme. The 32 parents, together with the 128 hybrids and 4 check varieties were evaluated for grain yield, yield components traits and drought tolerance under stress and non-stress environments. Data were analysed using GenStat statistical package following a fixed effects model. Non-additive gene action was predominant in controlling plant height, grain yield, above ground biomass, grain filling duration, 100-seed weight and panicle weight, whereas additive gene action was found more important in controlling days to 50% anthesis and panicle length. Novel landraces with high GCA effects were selected including 214838-A, 242039-B, 75454, 73056-B, and 242050-A which will serve as potential parents for cultivar development. Similarly, the study identified new experimental hybrids i.e. ICSA 749 x 242039-B, ICSA 756 x 242049-B, ICSA 756 x 75454, ICSA 756 x 73059 and ICSA 756 x 214855 with high SCA effects and heterosis for grain yield which will be forwarded for further stability analysis and farmers participatory selections at representative growing environments. In general, the study identified invaluable sorghum germplasm and candidate hybrids useful for further breeding and conservation strategies. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Sorghum (Sorghum bicolor) is the third most important cereal food crop in Uganda. However, the parasitic weed Striga hermonthica severely constraints its production. The use of Striga resistant sorghum varieties may be one of the most feasible ways of managing the Striga problem. A series of studies were carried out with the overall objective to develop new sorghum genotypes that are resistant to Striga and high yielding in Eastern Uganda. Initially, a participatory rural appraisal (PRA) was carried out with the main objectives to study the current constraints faced by farmers in sorghum production and determine their preferences for new sorghum varieties. Secondly, fifty different African sorghum accessions were evaluated to determine phenotypic and genotypic variability for Striga resistance and identify suitable parents to be used in breeding for new Striga resistant and high yielding sorghum genotypes. Thirdly, a genetics study was conducted to determine gene action responsible for Striga resistance and sorghum yield in new sorghum genotypes. Finally, laboratory studies were carried out to identify specific mechanisms of Striga resistance available in new sorghum genotypes and their parents. During the PRA, Striga was identified as the main constraint limiting sorghum production in Eastern Uganda, followed by insect pests. Farmers indicated preference for red gain sorghum with erect and compact heads, a plant height of 1.5m and a maturity period of around three months, as well as Striga resistance and drought tolerance. From farmers’ own assessments, the individual field surveys and soil seed bank analyses that were carried out, the degree of Striga infestation in farmers’ fields was found to be high. Both phenotypic and genotypic factors contributed significantly to the variability observed among the African sorghum accessions with respect to Striga resistance and sorghum crop performance indicating that Striga resistance can be improved through selection. However, techniques that minimise environmental effects need to be employed in order to improve on heritability. The values for genetic coefficient of variation (GCV) and genetic advance (GA) indicated that genetic gain for Striga resistance could be achieved by selection based on area under Striga severity progress curve (AUSVPC), area under Striga number progress curve (AUSNPC) and individual Striga emergence counts. The sorghum accessions SRN39, Brhan, Framida, Gubiye, Wahi, P9407 and N13 were found to be resistant to Striga hermonthica. These accessions consistently showed low AUSNPC, AUSVPC, and individual Striga emergence, Striga vigour and severity indices. These accessions could be used as sources of Striga resistance genes when breeding for Striga resistance in sorghum. In the study to determine gene action responsible for Striga resistance and sorghum yield, significant genetic variation for Striga resistance and sorghum yield parameters was observed among the new sorghum genotypes and their parents. The sorghum parental lines: Brhan, SRN39, Hakika and Sekedo consistently had negative GCA effects for AUSNPC and AUSVPC, while SRN39 and Hakika additionally had negative GCA effects for Striga vigour, indicating that they were effective in transferring Striga resistance into their progeny. The new genotypes: SRS1608, SRS3408, SRS2408, SRS4609, SRS3108, SRS2908, SRS2609, SRS609 and SRS1708 had negative SCA effects for AUSNPC, AUSVPC and Striga vigour meaning that they were resistant to Striga. Sorghum parental lines: Sekedo, Brhan, Framida and Hakika had positive GCA effects for head length, meaning that they increased head length in their crosses. The genotypes: SRS3408, SRS5309, SRS1608 and SRS2908 derived from the above parents had the longest heads compared to other progenies, which were on average, 20% longer than their parents. The genotypes: SRS609, SRS1408, SRS2608 and SRS3408 were the highest grain yielders and yielded 11-51% better than the highest yielding parent (Sekedo) under the non Striga environment. The parental lines; Sekedo, Brhan and Framida had positive GCA effects for grain yield indicating that they could act as sources of genes for grain yield increase. The genotypes; SRS609, SRS4609 and SRS2908 had large positive SCA effects for grain yield. The relative contributions of GCA effects to the observed genotypic variances were 80.5%, 43.3%, 65%, 92.6% and 53.2% for AUSNPC, AUSVPC, Striga vigour, sorghum head length and plant height respectively. This shows that additive gene action was important in controlling Striga resistance, sorghum head length and plant height in the present sorghum populations. Laboratory studies aimed at investigating the specific mechanisms of Striga resistance available in new sorghum genotypes found that two new sorghum genotypes, SRS1608 and SRS1208 expressed both the low germination stimulant character and low haustoria initiation as mechanisms of resistance to S. hermonthica. The sorghum genotypes, SRS2808 and SRS1108, and two fixed lines, Brhan and Hakika expressed only the low germination stimulant character, while the genotypes, SRS608, SRS3408, SRS4109 and SRS2308 expressed only the low haustoria initiation mechanism. The inheritance patterns of the low germination stimulant character in the present sorghum genotypes varied. In some genotypes, it appeared to be controlled by a single gene while in others; it appeared to be controlled by more than one gene. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Pigeonpea (Cajanus cajan (L.) Millsp.) is cultivated by many farmers in the semi-arid areas of Kenya as a source of food and cash. However, the yields have remained low, ranging between 500 to 800 kg haˉ¹. Apart from drought, fusarium wilt is reported to affect yield. Breeding pigeonpea hybrids, using cytoplasmic male sterile (CMS) lines, hybridized with the local improved germplasm, have the potential for increasing yield and improve income for smallholder farmers. The objectives of the study were to: 1) examine the various stakeholders of the pigeonpea value chain and their core functions and identify characteristics of the pigeonpea varieties preferred by the market to be considered in the hybrid breeding programme, 2) evaluate cytoplasmic male sterile lines of Indian origin for stability across several environments in Kenya, 3) screen pigeonpea genotypes for general resistance to Fusarim udum Butler and 4) evaluate pigeonpea hybrids for grain yield and earliness across sites and seasons in Kenya. The stakeholder analysis established that the main players in the pigeonpea value chain were farmers, traders/processors, International Crops Research Institute for the Semi-Arid Tropics, Kenya Agricultural Research Institute, Kenya Plant Health Inspectorate Services, and Ministry of Agriculture. White seed, large seed size and medium maturity were the preferred traits by farmers and processors/exporters for both domestic and export markets. The unavailability of quality seed in sufficient quantities of high yielding varieties was cited as the main factor negatively affecting pigeonpea production. The stakeholder analysis approach, used for the first time in a breeding programme, demonstrated that it can be an important tool that can be used to diagnose crop production constraints, and define opportunities available for setting up a breeding programme that is highly client-oriented. Two CMS lines, ICPA2043 and ICPA2039 were the most stable across sites with 100% and 99% pollen sterility respectively. Screening for the presence of physiologic races of F. udum based on morphological and cultural characteristics on PDA identified three distinct isolate groups named ISO-A, ISO-B, and ISO-C. Studies under controlled conditions using the three isolates identified seven pigeonpea genotypes (ICPB2043, ICP12012, ICP13092, ICPA2039xICP13092, ICPA2043xICP12012, ICPA2043xICP13092, ICPA2043xICP9135) resistant to the three F. udum isolates. In the field evaluation, seven genotypes (ICPA2039xICP13092, ICPA2039xAsha, ICPA2043x12012, ICPA2043xICP13092, ICPA2043xICEAP557, ICPB2043 and Maruti) were found to be moderately resistant. The variances due to GCA and SCA were significant, showing that both additive and non-additive gene actions were important. The resistant hybrid, ICPA2043xICP12012 had the highest negative SCA that was highly significant for all the isolates and in the field indicating general resistance. The CMS (A) line ICPA2043 was found stable across environments and highly resistant to the three F. udum isolates. Therefore, it can be evaluated further for commercial hybrid seed production in Kenya. Evaluation of the pigeonpea genotypes across environments indicated that the highest yielding environment was Kiboko, with average and maximum yield of 2,249 kg haˉ¹ and 4,234 kg haˉ¹ respectively. Most hybrids were in the medium duration maturity group with days to maturity ranging from 147 to 186. Overall, the highest yielding hybrids were A2043xTZ26 and ICPA2039xTZ24 with mean yields 2,803 kg haˉ¹ and 2,527 kg haˉ¹ respectively. Mean yields for the best performing parents were 2,036 kg haˉ¹ for ICP12012 and 1,629 kg haˉ¹ for Asha. For specific sites, the highest yielding hybrids in Kabete, Kiboko and Leldet were A2039xTZ24 (2,057 kg haˉ¹), A2043xTZ26 (2,803 kg haˉ¹), and A2043xUG8 (1,708 kg haˉ¹) respectively. Mean heterosis for yield varied from -35% (A2039xA2043) to 50% (A2043xUG8). In Kenya, the potential for production and commercialization of hybrid pigeonpea is feasible due to high hybrid vigour recorded, and the stability of the CMS lines. Hybrids also have greater uniformity in grain size a factor which is important for the market. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.