Common bean production in Tanzania is constrained by soil phosphorus which is mainly due to inherently low phosphorus content, soil erosion, and fixation by oxides in acidic soils. A study was conducted to evaluate bean genotypes in a screen house pot experiment for their ability to thrive and produce on low phosphorus soil. Assessment of shoot biomass, root biomass, shoot P concentration, P uptake, and yield components was done using three phosphorus levels and seven bean genotypes. Phosphorus levels, namely, control (P0), medium P (40 mg P/kg), and high P (160 mg P/kg), were the main plot factor, while the genotypes were the subplot in split plot structure, arranged in a completely randomized design. Shoot and root biomass as well as P uptake increased significantly with increase in phosphorus levels. There was varying response of genotypes in performance in terms of shoot biomass P uptake, and yield in a treatment without P addition. Genotypes MILENIO, BAT477, and A785 were outstanding in terms of root and shoot biomass, P uptake and grain yield under low P treatment. Therefore, those genotypes can be recommended for use in low-phosphorus environment as well as breeding materials.

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Alectra vogelii (benth) is parasitic weed which causes significant yield reductions in cowpea (Vigna unguiculataWalp) in Africa. The objective of this study was to identify the type of gene action controlling the trait for resistance to Alectra vogelii in cowpea and estimate the heritability of the trait. Seven genotypes of cowpea were mated in half diallel and their F 2 progeny, including parents, were evaluated for reaction to Alectra vogelii infection in the field in two locations at Ilonga and Hombolo Agriculture Research Stations. Highly significant (P < 0.001) differences were found for Alectra emergency and infestation at Ilonga. General combining ability (GCA) and specific combining ability (SCA) effects for Alectra shoot emergency and infestation were significant (P < 0.05). The estimate of Baker's ratio for Alectra shoot emergency and infestation were 0.62 and 0.66, respectively. This indicates that both additive and non-additive gene actions influenced the trait for resistance to Alectra emergency and infestation. Narrow sense heritability estimates were 41.28 and 44.39 for shoot and emergency, respectively. These results imply that introgression of a desirable trait in an elite genotype would involve careful crossing with a resistance genotype, accompanied by selection in the advanced population.

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A study was conducted to evaluate common bean (Phaseolus vulgaris L.) genotypes for drought tolerance in the Southern Highlands of Tanzania. Treatments included 18 genotypes laid out in a 3×18 split plot arranged in randomized complete block design with three replications. The data on yield under water stress and non-water stress treatments were used to calculate indices that can be used for predicting tolerant genotypes. This was accomplished by ranking the yield indices within the selection indices. Results showed that, selection index, YI, identified BFS60, KG104-72 and SER16 as the most tolerant genotypes, while STI, MP and GM identified SER16, BFS60 and KG104-72. Another index, SSPI, identified RCB266, 41-EX-VAM and SER83 as most sensitive genotypes to water deficit while HM showed BFS60, SER16 and KG104-72 as genotypes tolerant to drought. In contrast, SSI discriminated 41-EX-VAM, RCB266 and PASS as most susceptible genotypes under drought. Ranking the means of yield indices, genotypes SER16, BFS60 and KG104-72 were identified as the most drought tolerant genotypes. Correlation analysis showed that Yp were highly significant (p < 0.001) and positively correlated with STI, SSPI, MP, HM, and GM while Ys were highly significant (p<0.001) and positively correlated with YI, STI, MP, HM and GM. The findings suggest that these indices are effective for discriminating genotypes with higher yields under non stress and stress conditions, respectively. Genotypes, SER16, BFS60 and KG104-72 are among the most tolerant to drought conditions therefore are recommended for cultivation in drought prone environments and subsequently as parental materials in breeding for drought tolerance.

Angular leafspot (ALS), caused by the fungus, Pseudocercospora griseola, is one of the most important disease of common bean in Tanzania. Breeding for resistance to this disease is complicated by the variable nature of the pathogen. In Tanzania, a thorough analysis of the variability of this pathogen is lacking which limits breeding for durable resistance. This work aimed at characterizing P. griseola in relation to its host in Tanzania. A sample collection of both P. griseola and common bean was conducted in the 2013 and 2014 growing seasons from nine regions. Single spore isolation was performed for P. griseola isolates and DNA was extracted from both P. griseola mycelium and bean leaves from which the pathogen was collected. For characterization of the gene pool origin of the host, Phaseolin DNA marker was evaluated and for the pathogen, the Internal Transcribed Spacer region (ITS) and the Actin gene sequences were evaluated. Phylogenetic analysis showed the presence of 69.7% Andean and 30.3% Mesoamerican strains of P. griseola in Tanzania. The common bean host genotypes showed a similar distribution with 84.2% Andean and 15.8% Mesoamerican. In both cases, Andean strains of the pathogen and Andean bean genotypes outnumbered Mesoamerican. In relation to the common bean genotypes, Andean genotypes were more susceptible to ALS as compared to Mesoamerican genotypes. There were few strains that were of Andean origin but were pathogenic on Mesoamerican common bean genotypes, a group that has previously been termed Afro-Andean. Geographically, most of the regions of Tanzania had only Andean strains except for Kagera where 60% were Mesoamerican strains, and in Arusha and Tanga, where 50 and 33% were Mesoamerican, respectively. Only three regions, Kagera, Mbeya and Rukwa, were found to grow Mesoamerican beans. The findings of this study are important in setting basic objectives for breeding for angular leaf spot disease in Tanzania.

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