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.

The importance of maize in sub-Saharan Africa and the potential of quality protein maize (QPM) to alleviate the nutritional gap caused by lack of access to adequate protein rich foods were highlighted. Frustrations from complex inheritance systems of the QPM trait leading to calls for more information on the inheritance and stability of the QPM trait, fear of total loss of the QPM trait due to the recessive nature of the opaque-2 gene to the wild type gene in normal endosperm maize when QPM and normal endosperm maize coexist, lack of information on the nutritional value of contaminated QPM grain, and poor linkages with the smallholder farmers were all cited as drawbacks in the promotion and adoption of QPM. Therefore the objectives of the study were: 1) To solicit the participation of smallholder farmers in the development and setting up of QPM breeding goals, objectives and dissemination strategies; 2) To estimate general combining ability (GCA), specific combining ability (SCA) and reciprocal cross effects on anthesis days, quality traits and grain yield among the publicly available elite QPM inbred lines; 3) To compare experimental QPM hybrids with selected check cultivars, and normal endosperm maize hybrids for grain yield performance and kernel endosperm modification scores; 4) To evaluate QPM hybrids for grain yield and kernel endosperm modification scores in selected sub-Saharan Africa target environments. 5) To determine the level of normal endosperm maize pollen contamination that can occur in quality protein maize without loss of nutritional superiority; 6) To estimate the average levels and the patterns of foreign maize pollen contamination in QPM crops coexisting with normal endosperm maize varieties. The contribution of smallholder farmers in setting breeding goals and dissemination strategies for QPM was solicited. One major finding was that the kernel endosperm qualities of landrace “Hickory King” need to be incorporated into new QPM varieties so as to encourage adoption. Farmers preferred getting information on QPM varieties through their local Agricultural Research and Extension (AREX) officers. A diallel study of 36 F1 QPM hybrids and their reciprocals was conducted across seven environments for agronomic traits and three environments for nutritional value traits. There were significant differences for all traits analysed using Griffing Method 3 model 1. General combing ability effects were significant and important in the control of anthesis days, kernel endosperm modification, protein content, tryptophan content, and Quality Index (QI). Specific combining ability effects were highly significant and important in the control of grain yield. There were significant SCA effects for anthesis days and QI but the proportions were lesser than the corresponding GCA effects in both traits. Kernel endosperm modification had significant GCA effects and nonsignificant SCA effects. Reciprocal-cross differences were significant for anthesis days, tryptophan content and QI. Nonmaternal effects were significant for tryptophan content whilst both maternal and nonmaternal effects were significant for QI and anthesis days. Nonmaternal effects were relatively more important than maternal effects in all the cases where there were significant reciprocal-cross differences. The cross with the highest SCA effects for grain yield was CZL03016/CML144. The most desirable cross with the lowest anthesis days was CZL03016/CML144 whilst the most desirable inbred line with the lowest anthesis GCA effects was CZL03016. The inbred line with the most desirable GCA effects for protein content, tryptophan content and QI was CML264Q. Inbred line CML264Q crossed to CZL03016 had significant SCA effects for QI. The most desirable GCA effects for kernel endosperm modification were associated with inbred line CZL03016 followed by CZL01006. Maternal effects for both tryptophan content and QI were associated with inbred line CML264Q. Genotype by environment interaction effects across all the seven environments were significant for grain yield and kernel endosperm modification. Check hybrids performed better than experimental hybrids for grain yield but were not different for kernel endosperm modification. The normal endosperm maize hybrids were significantly better for both grain yield and kernel endosperm modification. However, in all the comparisons the best check or normal endosperm maize hybrid was not significantly better than the best experimental or QPM hybrid, respectively. The most desirable score for kernel endosperm modification was from the cross of CZL01006 to CZL03016 though not significantly different from the check hybrid with the best score. AMMI1 was the best model for kernel endosperm modification scores and AMMI2 was suitable for grain yield. Both environments and hybrids were diverse. Grain yield of most hybrids was not stable with specific adaptation to environments. The most stable hybrid with no specific adaptation was CML176/CML181f with a mean yield of 6.51t ha-1. The putative nutritional superiority of normal endosperm maize pollen contaminated QPM as measured by the QI depended on the environmental conditions. The moisture stressed environment (CIMMYT Harare) had a lower QI value (0.858) and a lower tolerance to pollen contamination of 15.3% whereas the grain produced under near to optimum growing conditions (ART farm) had a higher QI value (0.915) and a higher tolerance to pollen contamination of 31.9% before total loss of nutritional superiority. Thus contaminated QPM grain had nutritional superiority up to a certain point before total loss of nutritional superiority. Geostatistical analysis was used to determine the levels and patterns of pollen contamination that occur when QPM and normal endosperm maize crops coexist under conditions minimising both temporal and geographical isolation to the lowest possible levels for the two independent crops. Higher pollen contamination levels were restricted mostly to the sections of the QPM crop proximal to the rows of normal endosperm maize crop, with the central parts of the QPM crops experiencing relatively low levels of contamination. For the four experiments (QCS200711, QCS200712, QCS200721 and QCS200722) in which the thresholds to nutritional superiority were determined, 87.9%, 94.8%, 62.2% and 65.6% of the crop areas passed for superior QPM grain, respectively. Estimates for average contamination levels of homogenous mixtures of grain from each of the nine experiments were below 20% contamination. The contamination levels were far less than previously thought. “Hickory King” kernel quality attributes were important in breeding QPM varieties for the smallholder farmers. Parents of the 72 hybrids were diverse for the agronomic characters studied and three of the experimental hybrids were found to be adapted and comparable to the check varieties. Quality protein maize tolerance to foreign pollen contamination without loss in nutritional superiority depended on growing conditions. The coexistence of QPM and normal endosperm maize without total loss of QPM nutritional superiority was feasible. / Thesis (PhD.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

There are few maize varieties that are drought tolerant in semi-arid eastern Kenya and farmer perceptions of drought tolerant maize cultivars have not been studied in this region. Farmers in this region use maize landraces that have not been studied for their potential future hybridization. The main objectives of this study were therefore to: (i) study farmer perceptions of drought and preference for maize varieties, (ii) improve drought tolerance in maize populations in the semi-arid eastern Kenya using S1 family recurrent selection, and (iii) classify maize landraces according to their heterotic patterns. A participatory rural appraisal (PRA) was conducted in Machakos and Makueni districts in semi-arid eastern Kenya. A total of 175 farmers were involved in focus group discussions. An open ended questionnaire and a checklist were used to guide the farmers during the discussion sessions. Scoring and ranking techniques were used to assess farmers’ preferences of maize varieties and constraints to maize production. The farmers grew maize as their major crop followed by beans. Nearly 60% of the farmers grew local maize landraces, whose seed they recycled from season to season; 40% grew improved varieties, but mainly composites rather than hybrids. The key farmers’ criteria for choosing a maize variety in order of importance were drought tolerance, early maturity, high yield, and disease resistance. The major constraints to maize production were drought, lack of technical know-how, pests, poor soils, and inadequate seed supply. Maize traits preferred by farmers in a drought tolerant variety included high yield, recovery after a dry spell and the stay green characteristic. Two maize landrace populations MKS and KTU from semi-arid eastern Kenya and three CIMMYT populations V032, ZM423, and ZM523 were subjected to two cycles of S1 progeny recurrent selection for drought tolerance in yield and traits indicative of drought tolerance were measured during flowering and grain filling from February 2005 to September 2007. Evaluation to determine selection gains was done in one trial replicated five times. It was laid out as a 4x4 lattice design and drought was imposed at reproductive stage by withholding irrigation one week before flowering and resumed during grain filling. The trial was repeated under well-watered conditions which served as a control experiment. After two cycles of selection under drought stress conditions, KTU population had a realized gain in yield of 0.2 t ha-1, MKS population 1.2 t ha-1 and ZM423 0.4 t ha-1, whereas in V032 and ZM523, grain yield reduced by 1.1 t ha-1 and 0.6 t ha-1, respectively. Under well watered conditions, the realized gains in grain yield were positive in all the populations except V032, where there was a reduction of 0.1 t ha-1. Selection increased the genetic variability and heritability estimates for yield in S1 lines of MKS and ZM423 populations, but decreased in KTU, V032 and ZM523 populations. The research to identify heterotic patterns was undertaken using ten maize landraces from the semi-arid eastern Kenya, six maize landraces from coastal Kenya, and three maize populations from CIMMYT. These populations were planted at Kiboko Research Farm during the short rains of October-December 2005 and crossed to two population testers, Embu 11 and Embu 12. The evaluation of the test crosses was done during the long rains of March-June 2006. Percentage heterosis for yield ranged from -17.7% to 397.4%, -79.4 to 22.2% for anthesis-silking interval, -23.9% to 29.2% for ear height, -0.1 to 1.1 for ear diameter, -7.1 to 21.2% for ear length and -5.9% to 30.3% for plant height. iii General combining ability (GCA) effects were significant (p=0.05) for all the traits, while specific combining ability (SCA) effects were not significant (p>0.05), implying that variation among these crosses was mainly due to additive rather than nonadditive gene effects. Since SCA was not significant (p>0.05) for yield, maize populations were classified based on percentage heterosis for yield alone. The maize populations therefore, were grouped into three different heterotic groups P, Q and R. Twelve landrace populations and two CIMMYT populations showed heterosis with Embu 11 and no heterosis with Embu 12 were put in one group P. Two landrace populations that showed no heterosis with either tester were put in group Q. Two landrace populations and one CIMMYT population showed heterosis with both testers were put in group R. None of the populations showed heterosis only with Embu 12 and no heterosis with Embu 11. The main constraint to maize production was drought and the farmers preferred their landraces whose seed they recycled season to season. After two cycles of recurrent selection, the landrace populations showed improved progress in yield. Thus, further selection will be beneficial in the populations where genetic variability increased. Therefore, these populations can further be improved per se and released as varieties and/or incorporated into the existing maize germplasm to broaden their genetic base, given that their heterotic patterns have been identified. Considering that farmers recycle seed, breeding should be towards the development of open-pollinated varieties which are drought tolerant. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

In Southern Africa and Mozambique, tropical lowland accounts for 22% and 65%, respectively, of area under maize production, but grain yield is compromised by downy mildew disease (DM, which is caused by Peronosclerospora sorghi (Weston and Uppal) Shaw), and lack of appropriate varieties, especially hybrids. Among other factors, productivity can be enhanced by deploying DM resistant hybrids, which are higher yielding than open pollinated varieties. Development of a viable hybrid-breeding programme requires knowledge of genetic effects governing yield and DM resistance in inbreds, and effective germplasm management requires heterotic groups and heterotic patterns to be established. In addition, knowledge of farmer-preferred traits is required. Currently, such information is not available to the hybrid-breeding programme in Mozambique. The objectives of this study were, therefore; i) to identify farmers’ preferred variety traits and major production constraints, ii) to determine combining ability effects of inbred maize S4 lines for grain yield and DM resistance, iii) to determine heterotic groups and heterotic patterns among the elite inbred maize lines, and iv) to investigate gene effects governing resistance to DM in breeding source inbred maize lines from the breeding programme in Mozambique. During 2007/08, 142 households were involved in a survey conducted in three districts representing two maize agro-ecological zones in Mozambique. Formal surveys and informal farmer-participatory methods were employed and data subjected to analysis in the SPSS computer programme. Results indicated that there was a low utilization of improved varieties, especially hybrids, with grain yield estimated at 0.7 t ha-1. Farmers were aware of the major production constraints and could discriminate constraints according to their importance for their respective communities. For the lowland environment, farmers identified downy mildew, drought, and cutworm and stem borer damage as the main constraints. In contrast, for the high altitude environments, they ranked ear rot, seed and fertilizer availability, turcicum leaf blight, grey leaf spot diseases and low soil fertility among the major constraints limiting productivity. The most important variety selection criteria were grain yield, short growth cycle, white and flint grain with stress tolerance to drought, low soil fertility, diseases, and grain weevils. These afore mentioned traits, would be priority for the breeding programmes for the lowland and mid altitude environments in Mozambique. To determine combining ability for downy mildew resistance, heterotic groups and heterotic patterns, two testers (open-pollinated varieties) ZM523 (Z) and Suwan-1 (S), were crossed with 18 lines to generate 36 top crosses for evaluation. Crosses were evaluated at two sites under DM. Preponderance of GCA effects indicated that additive gene effects were more important than non-additive gene effects in governing both grain yield and downy mildew resistance in the new maize lines. Based on specific combining ability (SCA) data, lines for yield were classified into two heterotic groups, S and Z; whereas based on heterosis data, lines were fitted into three heterotic groups (S, Z and SZ). Further heterotic patterns and gene action for yield were determined by subjecting nine inbred lines and the two testers, S and Z, to an 11 x 11 diallel-mating scheme. The diallel crosses, three hybrid checks and the two testers were evaluated in six environments in Mozambique. Results revealed that non-additive gene effects were predominant for yield components. In addition, high levels of heterosis for yield was observed and three heterotic groups identified (Z, S and S/Z), and five exceptional heterotic patterns among the inbred elite maize lines were observed. Topcrosses with yield levels comparable to single cross hybrids were also identified, and these would be advanced in the testing programme with potential for deployment as alternative cheaper and sustainable technology to conventional hybrids for the poor farming communities in Mozambique. To determine gene effects for downy mildew resistance in potential breeding lines, two maize populations were derived from crosses between downy mildew susceptible line LP67, and resistant lines DRAC and Suwan-L1. To generate F2 and backcross progenies (BCP1 and BCP2), F1 progenies were self-pollinated and simultaneously crossed to both inbred parents (P1 and P2). All the six generations (P1, P2, F1, F2, BCP1, and BCP2) of the populations were evaluated at two sites under downy mildew infection. A generation mean analysis was performed in SAS. It was revealed that downy mildew resistance was influenced by genes with additive and dominance effects, plus different types of epistatic effects such as additive x additive, and dominance x dominance. Overall results indicated that genes with predominantly non-additive effects controlled resistance in DRAC, whereas resistance in Suwan-L1 was largely influenced by additive gene effects. These findings have serious implications on the effective use of these downy mildew resistance sources in breeding programmes that aim to generate varieties with downy mildew resistance. Overall, results suggested that inbreeding and selection within heterotic groups, followed by hybridization between inbreds within and across heterotic groups would be effective to generate new hybrids. The breeding programme will consider development of conventional hybrids, such as single crosses and three way crosses, and top crosses. Implications of the findings of the study and recommendations are discussed. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Abstract not available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Quality protein maize (QPM) has high nutritional value, but production is threatened by downy mildew (DM) and maize streak virus disease (MSVD) among other constraints. There are few studies of DM and MSVD resistance in QPM cultivars. The objective of this study was to improve resistance to DM and MSVD in three QPM populations. This was realized through ascertaining farmers’ key production constraints and special preferences for cultivars; determining the utility of recurrent selection method for improvement of three QPM populations (SussumaS2, ZM521Q and Pop62SRQ); and determining grain yield potential. The study was conducted in Mozambique for DM and in Zimbabwe for MSV, during 2003 to 2006. Surveys were conducted in Manica and Angonia districts in Mozambique to ascertain farmers’ perceptions and preferences for maize varieties, especially QPM. Participatory rural appraisal tools that included semi-structured questionnaires and focus group discussions were used to collect data. Results showed that farmers predominantly grew open pollinated varieties and fewer normal maize hybrids (non-QPM), and grain yield was estimated to be very low (0.2 to 0.6 t ha-1). Results showed that drought and insect pests were the dominant constraints to maize productivity in Mozambique, while diseases were ranked third. Downy mildew disease and MSVD were considered to be the most important diseases reducing maize productivity. Farmers also showed high preference for high yielding and early maturity cultivars in all areas. Predominantly, farmers were still using their local landraces because of sweet taste, particularly for home consumption and flint grain for storage. Farmers’ access to improved cultivars was limited due to high seed prices on the local market. Research priorities as perceived by the farmers included breeding for resistance to drought, grain weevils and diseases and sweetness. Generally, farmers showed little knowledge of QPM varieties and the importance of this trait, but they observed that the few QPM varieties they knew had some weaknesses such as poor storability and susceptibility to DM and MSVD which required improvement. These results should be considered in breeding new cultivars, both normal and QPM. To improve DM and MSV disease resistance in QPM varieties, S1 recurrent selection was conducted in three QPM populations, Sussuma, ZM521Q and Pop62SRQ at Umbeluzi Research Station in Mozambique and at CIMMYT-Harare Research Quality protein maize (QPM) has high nutritional value, but production is threatened by downy mildew (DM) and maize streak virus disease (MSVD) among other constraints. There are few studies of DM and MSVD resistance in QPM cultivars. The objective of this study was to improve resistance to DM and MSVD in three QPM populations. This was realized through ascertaining farmers’ key production constraints and special preferences for cultivars; determining the utility of recurrent selection method for improvement of three QPM populations (SussumaS2, ZM521Q and Pop62SRQ); and determining grain yield potential. The study was conducted in Mozambique for DM and in Zimbabwe for MSV, during 2003 to 2006. Surveys were conducted in Manica and Angonia districts in Mozambique to ascertain farmers’ perceptions and preferences for maize varieties, especially QPM. Participatory rural appraisal tools that included semi-structured questionnaires and focus group discussions were used to collect data. Results showed that farmers predominantly grew open pollinated varieties and fewer normal maize hybrids (non-QPM), and grain yield was estimated to be very low (0.2 to 0.6 t ha-1). Results showed that drought and insect pests were the dominant constraints to maize productivity in Mozambique, while diseases were ranked third. Downy mildew disease and MSVD were considered to be the most important diseases reducing maize productivity. Farmers also showed high preference for high yielding and early maturity cultivars in all areas. Predominantly, farmers were still using their local landraces because of sweet taste, particularly for home consumption and flint grain for storage. Farmers’ access to improved cultivars was limited due to high seed prices on the local market. Research priorities as perceived by the farmers included breeding for resistance to drought, grain weevils and diseases and sweetness. Generally, farmers showed little knowledge of QPM varieties and the importance of this trait, but they observed that the few QPM varieties they knew had some weaknesses such as poor storability and susceptibility to DM and MSVD which required improvement. These results should be considered in breeding new cultivars, both normal and QPM. To improve DM and MSV disease resistance in QPM varieties, S1 recurrent selection was conducted in three QPM populations, Sussuma, ZM521Q and Pop62SRQ at Umbeluzi Research Station in Mozambique and at CIMMYT-Harare Research. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Low soil nitrogen (N) and drought impede maize production in the small-scale farming sector in Zambia; and adoption of new cultivars with improved tolerance might enhance production. This study: a) assessed farmer preferences for maize cultivars; b) determined genotype x environment interaction effects among popular maize cultivars under contrasting soil fertility levels and; c) investigated landraces for tolerance to low N and drought using S1 selection. The study was carried out in Zambia from 2004-07. Farmer preference influencing the adoption of maize cultivars was investigated using both formal and informal surveys in Luangwa, Chibombo and Lufwanyama rural districts representing the three agro-ecological regions of Zambia. Focus group discussions and personal interviews were used to collect data on issues that affected maize production in these areas. It has been found that although farmers perceived landraces to be low yielding, they believed that they were superior to improved cultivars for: tolerance to drought; tolerance to low soil fertility; grain palatability; grain storability; and poundability. The need for food security, their inability to apply fertiliser, and their need for drought tolerant cultivars significantly (p ≤ 0.05) influenced farmers in adopting cultivars. The farmers would readily adopt cultivars that address these concerns. The predominant use of certain landraces (76%) reflected their superiority in meeting some of these needs. The performance of nine popular cultivars (three for each of hybrids, OPVs and landraces) under contrasting levels of soil fertility, across six environments (ENVs) in the three agro-eological regions, was evaluated. An ENV was defined as season x location combination. The fertilizer treatments were full fertilization, basal dressing, top dressing and nil fertilization. The cultivars exhibited significant non-crossover type of genotype x fertilisation interaction effects at three ENVs, while the genotype x fertilisation interaction effects, were non-significant at the other three ENVs. The cultivars exhibited dynamic stability by increasing grain yield (GY) when fertilization was increased. Landraces yielded higher than all open pollinated varieties and were generally higher yielding than two hybrids. Based on average rank for GY, the five highest yielding cultivars were MRI724, Gankata, MM603, Kazungula and Pandawe. Superiority of landraces revealed their genetic potential for GY under low soil fertility and they should be used as germplasm in developing cultivars targeting such environments. Ninety-six local landraces were selfed to generate S1 lines (2004/05 season) which were crossed to a tester (2005/06 season). Testcrosses were evaluated under optimal, low N, and drought conditions (2006/07 season). Data on GY, anthesis-silking interval, number of ears per plant, leaf senescence, leaf rolling, tassel size and grain texture were recorded in all the trials during the study period. Testcrosses, their S1 parents and landraces that were superior under low N, drought, optimal conditions and across environments were identified; these should be used to develop varieties targeted to a particular environment. Selection for tolerance to drought also selected for tolerance to low N. Selection for low N tolerance also selected for GY under drought and optimal conditions. Therefore, in selecting for tolerance to abiotic stresses, use of optimal and managed stress environments was effective. The following landraces were superior at 10% selection intensity: LR38, LR84 and LR86 (optimal, low N and drought conditions); LR11, LR35 and LR76 (low N and drought conditions); LR12 (optimal and drought conditions); LR40 and LR93 (low N conditions only); LR79 (drought conditions only) and; LR74 and LR85 (optimal conditions only). These landraces should be used as source germplasm targeting respective environments. Significant (p ≤ 0.05) positive general combining ability effects for GY under both low N and drought conditions were found implying that additive gene action conditioned GY under the abiotic stresses. The heritability for GY under low N (0.38), and drought (0.17) conditions, was low suggesting that selection based on GY alone was not effective. The genetic correlation for GY between optimal, and either low N (rG=0.458), or drought (rG = 0.03) environments, was low (rG < 0.5) suggesting that indirect selection would not be effective either. Therefore, use of secondary traits for selection is discussed. The study established that most farmers depended on local landraces for seed and would adopt low input improved varieties that yield higher than the landraces. Some landraces were found superior to some improved cultivars under contrasting fertilisation regimes. The study also found that landraces had genetic variation for tolerance to low N and drought. Landraces, S1 lines and testcrosses superior under low N, drought, optimal conditions and across environments were selected and they should be used to develop cultivars targeting respective environments. Policy implications of these results are discussed. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Maize (Zea mays L.) is the principal crop of Southern Africa but production is threatened by gray leaf spot (Cercospora zea-maydis L.) and phaeosphaeria leaf spot (Phaeosphaeria maydis L.) diseases, drought and the use of unadapted cultivars, among other constraints. There are few studies of gray leaf spot (GLS) and Phaeosphaeria leaf spot (PLS) resistance, drought tolerance, yield stability and maize cultivar preferences in Southern Africa. The objective of this study was to: a) determine farmers’ preferences for cultivars; b) investigate the gene action and heritability for resistance to GLS and PLS, and drought tolerance; and c) evaluate yield stability and its relationship with high yield potential in Southern African maize germplasm. The study was conducted in South Africa and Zimbabwe during 2003 to 2004. A participatory rural appraisal (PRA) established that farmers preferred old hybrids of the 1970s because they had better tolerance to drought stress. Farmers also preferred their local landrace because of its flintier grain and better taste than the hybrids. The major prevailing constraints that influenced farmers’ preferences were lack of appropriate cultivars that fit into the ultra short seasons, drought and low soil fertility. Thus they preferred cultivars that combine high yield potential, early maturity, and drought tolerance in all areas. However, those in relatively wet areas preferred cultivars with tolerance to low soil fertility, and weevil resistance, among other traits. A genetic analysis of 72 hybrids from a North Carolina Design II mating revealed significant differences for GLS and PLS resistance, and drought tolerance. General combining ability (GCA) effects accounted for 86% of genetic variation for GLS and 90% for PLS resistance indicating that additive effects were more important than non-additive gene action in controlling these traits. Some crosses between susceptible and resistant inbreds had high resistance to GLS suggesting the importance of dominance gene action in controlling GLS resistance. Resistance to GLS and PLS was highly heritable (62 to 73%) indicating that resistance could be improved by selection. Also large GCA effects for yield (72%), number of ears per plant (77%), and anthesis-silking interval (ASI) (77%) under drought stress indicated that predominantly additive effects controlled hybrid performance under drought conditions. Although heritability for yield declined from 60% under optimum to 19% under drought conditions, heritability for ASI ranged from 32 to 49% under moisture stress. High heritability for ASI suggested that yield could be improved through selection for short ASI, which is positively correlated with high yield potential under drought stress. The stability analyses of the hybrids over 10 environments indicated that 86% had average stability; 8% had below average stability and were adapted to favourable environments; and 6% displayed above average stability and were specifically adapted to drought stress environments. Grain yield potential and yield stability were positively correlated. In sum, the study indicated that farmers’ preferences would be greatly influenced by the major prevailing constraints. It also identified adequate genetic variation for stress tolerance, yield potential and yield stability in Southern African maize base germplasm, without negative associations among them, suggesting that cultivars combining high yield potential, high stress tolerance and yield stability would be obtainable. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Maize (Zea mays L.) production is constrained by a number of stresses, amongst the most important are gray leaf spot (GLS) caused by a fungus Cercospora zeaemaydis Tehon and E.Y. Daniels and Phaeosphaeria leaf spot (PLS) caused by Phaeosphaeria maydis (Henn.). The diverse germplasm comprising farmer collections and exotic material used in the medium and highland altitudes maize breeding programmes in western Kenya has not been improved for resistance to the two diseases. Heterotic patterns of germplasm from this region have also not been studied. Therefore, the objectives of this study were to (i) assess the prevalence, importance, and farmers’ perceptions of GLS and PLS, (ii) characterize maize germplasm collections into their heterotic groups and (iii) improve four maize populations for GLS and PLS resistance through recurrent selection. The participatory rural appraisal (PRA) was conducted at three sites in western Kenya during the 2005/2006 cropping season. Data was generated using a checklist in group discussions with 109 male and 123 female farmers as well as key informants. Constraints were identified and prioritised. The five most limiting, in order of importance, were low soil fertility, poor varieties and seed, drought, Striga, pests and diseases (GLS and PLS). Gray leaf spot and PLS were reported in all sites but farmers did not know the causes of these diseases. Farmers preferred local varieties Tiriki, Anzika and Kipindi due to their greater resistance to diseases than commercial hybrids. Farmer criteria for variety selection were low fertilizer, Striga and disease resistance, drought tolerance, closed tips, and high yield potential. Due to the high cost of hybrid seed farmers selected and planted their own seed from advanced generations from previous seasons. Across all the sites, yield gap between on-farm and expected yield potential was estimated as ranging from 4.73t ha-1 to 5.3t ha-1 mainly due to the identified constraints. Therefore maize breeding should focus on addressing important maize production constraints and farmers’ preferences identified in this study in developing varieties that will increase maize yields on-farm. During 2005/2006, seventy 77 testcrosses were developed through crossing 47 germplasm collections with four population testers, Kitale synthetic II (KSII), Ecuador 573 (EC 573), Pool A and Pool B. Crosses and testers were evaluated at Kakamega during 2006/2007 in a 9 x 9 triple lattice design. Significant (p < 0.05) differences in grain yield, ear height, days to 50% anthesis, GLS and PLS resistance were observed. Both general and specific combining ability effects (GCA and SCA, respectively) were significant (p < 0.01), with SCA accounting for more than 50% of the variation for GLS, PLS and yield and less than 50% for ear height, days to 50% anthesis and silk. This indicated that both additive and non-additive gene effects were important but non-additive gene effects were more important in conditioning these traits. High SCA effects indicated high heterosis between collections and populations. Both yield heterosis and SCA were used to study heterotic patterns, but percentage yield heterosis data was used to classify these materials into heterotic groups. Based on significance (p < 0.05) of percentage yield heterosis as a primary factor for classification, seven collections were classified to Pool A, 17 to Pool B, 12 to KSII and 6 to EC 573 heterotic groups. The study indicated that germplasm collections belong to distinct heterotic groups therefore they can be infused into these populations (Pool A, Pool B, KSII and EC 573). Four populations, KSII, EC 573, Pool A and Pool B were subjected to one cycle of reciprocal recurrent selection (RRS) and two cycles of simple recurrent selection (SRS) during the 2004-2006 cropping seasons at Kakamega. Response to selection was assessed by evaluating C0, C1 and C2 and four commercial checks in a randomised complete block design in three replications at Kakamega and Kitale during 2007. All cycles except C0 of Pool A were more resistant to GLS than the three checks, H623, KSTP94 and PHB3253. Response to selection for GLS was significant (p < 0.01) in the desired direction. Gains ranged from -32.2% to 6.4% cycle-1 for RRS and 0.0% to -61.3% cycle-1 for SRS. Heritability estimates of between 59% and 76.3% for GLS and 39% and 80% for PLS were observed indicating that both GLS and PLS can be improved through selection. Significant negative correlations between GLS and yield were observed in Pool A C0 (r = -0.947, p < 0.01) and between yield and PLS in Pool A C0 (r = -0.926, p < 0.01). These indicated gain in yield as GLS and PLS were selected against. Generally, SRS out performed RRS method both in genetic gain and time, as indicated by gain of -61% for SRS and -32.2% for RRS, respectively. Two cycles of selection were achieved in two years with SRS as compared to only one with RRS. These results clearly demonstrated that it is possible to improve for GLS resistance using simple and reciprocal recurrent selection methods. The main constraints to maize production in Western Kenya were low soil fertility, Striga, drought, lack of seed and diseases. Farmers preferred varieties that can do well under the constraints mentioned. Local collections belonged to distinct heterotic groups with good resistance to GLS and PLS and were highly heterotic to four maize population testers with both SCA and GCA effects being important in conditioning GLS and PLS resistance. Recurrent selection methods were found to improve maize resistance to GLS and PLS. Breeding should therefore, focus in development of hybrids and improvement of populations using these local collections by employing SRS and RRS selection methods with identified constraints and farmer preferences in mind. / Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2007.

Maize (Zea mays L.) yields in the smallholder (SH) farming sector in Southern Africa have remained low. despite the availability of many improved varieties. Among the major constraints contributing to tow yields and threatening food security in the region are diseases which include grey leaf spot (GLS). common rust, northern corn leaf blight (NLB) and Phaeosphaeria leaf spot (PLS). These diseases are highly unpredictable in their occurrence every season, making them difficult to control. In addition, the majority of SH farmers cannot afford to control the diseases due to limited access to chemicals. Therefore, maize cultivars with high levels of disease resistance and tolerance to abiotic stresses would provide a long-term solution to addressing the problem of low yields, especially in the smallholder-farming sector. The objectives of this study were therefore to: i) establish farmers' perceptions on diseases, key limiting production constraints and preferred traits of maize cultivars. ii) screen germplasm adapted to tropical environments for resistance to PLS, iii) determine gene action for resistance to PLS and GLS, iv) estimate combining ability effects for resistance to PLS, GLS, NLB and common rust diseases, and v) determine grain yield stability of F, hybrids derived from crosses among selected tropical advanced maize inbred lines. These studies were conducted from 2006/7 to 2008/9 seasons at various sites in South Africa, Zimbabwe, Zambia and Uganda. Structured surveys and participatory rural appraisal (PRA) conducted in Obonjaneni. Busingatha and Okhombe villages of Amazizi district in the Northern Drakensberg established maize as the principal crop grown in the area. All the farmers who participated grew the local variety (landrace) they called Natal-8- row or Is/Zulu. The adoption of hybrids and improved open pollinated varieties (OPVs) was tow. Farmers preferred the local variety ahead of hybrids and improved OPVs mainly for its taste, tolerance to abiotic stresses and yield stability. Characteristics of maize varieties preferred by the farmers included: inexpensive seed, high yield, early maturity and tow input costs. Pests/d is eases and drought were not ranked highly, as farmers planted early to escape diseases and drought. Abiotic stresses were amongst the top four constraints faced by the farmers. The local varieties exhibited high yield potential and genetic variability fordisease resistance. Evaluation of maize germplasm adapted to tropical and subtropical environments of Africa for PLS resistance indicated significant (PS0.05) variation among the inbreds. populations and hybrids. In general, 63% of the inbreds/populations were resistant to PLS. Regionally important inbred lines; SC and N3 and CIMMYT's most successful lines such as CML395. CML444. CML202. CML312. and CML488 were resistant to PLS. Fifty- four percent of the single-cross experimental hybrids were also resistant to PLS. Correlation coefficients for area under disease progress curve (AUDPC) values for disease severity with PLS final disease severity scores were significant (P<0.001) and positive, implying that ranking of the genotypes for AUDPC and final PLS disease severity score was by and large similar. Forty five F, hybrids generated by crossing ten advanced maize inbred lines in a half diallel mating scheme were evaluated in two to six environments to determine combining ability, gene action and heterosis estimates for grain yield and resistance to PLS. GLS. NLB and common rust diseases. Highly significant (PS0.001) general combining ability (GCA) and specific combining ability (SCA) effects were observed for PLS. GLS. NLB. common rust, grain yield and other agronomic traits. The GCA effects were more important than SCA effects, indicating the predominance of additive over non-additive gene action for all the traits studied in these inbred lines. The inbred lines with good GCA for PLS resistance were: A12204, N3. A16. MP18 and CML488. and for GLS resistance were A1220-4. CZL00009. CZL00001. CML205 and CML443. Lines A16 and CML443 had good GCA for NLB and common rust resistance, lines A1220-4, N3, CML205, A16, and CML443 contributed towards high yield. Lines A1220-4 and A16 were late maturing, whereas CZL00009 displayed eariy maturity. High mid-parent and better-parent heterosis for high grain yield and resistance to all the diseases were observed. Generation mean analysis was used to deteimine the inheritance of PLS and GLS resistance in populations involving six tropical advanced maize inbred lines. Reciprocal crosses and backcross progenies were generated among inbreds A1220-4, A15, B17 (resistant. R), CML445 (moderately resistant. MR). CML441 and CZL00001 (susceptible. S) for PLS inheritance, and among inbreds A1220-4. A15, CML441 (resistant. R). and N3 and B17 (susceptible. S), for GLS inheritance. Results indicated highly significant additive effects (P<0.001) for PLS and GLS resistance, with dominance effects accounting forSH%of the variation in all the crosses for PLS and only A15 x B17 cross for GLS. Epistasis and cytoplasmic gene effects in favour of PLS resistance in F, crosses when the more susceptible parent was used as female were significant. For GLS resistance, epistasis was observed only in CML441 x N3 and A1220-4 x B17 crosses, while no cytoplasmic gene effects were detected. Resistance for PLS was medium to highly heritable and conditioned by less than four genes which exhibited incomplete dominance. In general resistance to GLS was controlled by two to three genes exhibiting zero to partial dominance and was moderate to highly heritable. Stability analysis of the hybrids was done over 11 environments using the additive main effects and multiplicative interaction (AMMI) and the genotype and genotype by environment (GGE) biplot analyses. Both AMMI and GGE biplot analyses selected hybrids H21 (CZL00009 x A16). H14 (A1220-4 x A16). S63 (SeedCo hybrid check). N72 (MP72/N3) and H26 (CZL00001 x A16) as stable and high yielding. Hybrids H1 (CML445 x A1220-4), H44 (CZL00009 x CML443) and H18 (CZL00009 x CZL00001) were identified by both methods as unstable but high yielding. AMMI and GGE biplot analyses identified ZAM08, C108, RAO9 and C09 as the most representative environments which were high yielding and relatively stable. In general, the study has revealed that based on the farmers ranking of the constraints in their area, breeding opportunities do exist for incorporating tolerance to both biotic and abiotic stresses in their varieties. It also identified maize lines resistant to the main foliar diseases, with good combining ability and heterosis for resistance and high grain yield. Hybrids with wide adaptation and high yields across environments were also observed. The experimental hybrids that exhibited high levels of resistance can be recommended for further testing and release. On the whole, highly significant additive effects and moderate to high heritability estimates observed for all the diseases and grain yield implied progress would be made through selection, although significant epistasis and dominance could slow progress. Dominance effects towards resistance and high yield could be exploited in developing single cross maize hybrids among these inbreds when only one parent is resistant. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.