Breeding for resistant varieties has been shown to be the most suitable method to control bean anthracnose caused by Colletotrichum lindemuthianum though the method is challenged by the existence of many races of the pathogen. This work focused on characterizing races of C. lindemuthianum from potential bean agro ecological zones of Tanzania using a set of differential bean cultivars. From 144 anthracnose infected bean samples collected, 50 pure isolates were obtained and characterized whereby 42 races were identified. The most virulent race identified was race 3610 from the Southern Highland zone of Tanzania while the least virulent was characterized as race 0. Race 2 was the most widely spread (4.2 %) found in Northern, Southern highland and in Eastern zones of Tanzania. The work confirms that G2333 can still be used as a potential donor of resistant genes to varieties that are to be grown in Northern, Eastern and Lake zones but not for the varieties from Southern Highland and Western zones of Tanzania since isolates from these zones overcame resistant genes Co-4 2 , Co-5, Co-7 in G2333. 95% of all races which were identified are new and were not specific to either Mesoamerican or Andean origin common bean.

Common bean (Phaseolus vulgaris) is a rich source of protein, vitamins, and micronutrients and is an important crop for food security throughout Latin America, Asia, and Africa. Among tropical and subtropical regions of the world, where the majority of beans are grown, yield losses due to the pathogenic fungus Pseudocercospora griseola, causing angular leaf spot (ALS), can be as high as 80%. The strategic use of marker-assisted selection (MAS) to pyramid multiple resistance genes into a single genetic background with preferred morphological and cooking characteristics is being implemented by six research groups throughout East Africa that make up the African Bean Consortium (ABC). Identifying unique markers that are polymorphic among multiple parents is a major source of marker attrition. In this study, an illustration of how 22 DNA sequences physically linked to the Phg-2 ALS resistance locus were identified using the PhaseolusGenes marker database and checked for amplification and polymorphism among 16 ABC breeding parents are given. Only three polymorphic markers could be identified following this procedure; one (g796), showed a polymorphism present only in the ALS resistance donor, Mexico 54. The PCR protocol developed to identify the g796 polymorphism was validated among five laboratories. Furthermore, co-segregation analysis of the marker and ALS resistance phenotype in a population of 100 F 2 individuals from the cross between French bean (that is, green bean) genotype Amy and ALS resistance donor Mexico 54 showed the marker is genetically linked (3 cM) to the Phg-2 locus, in addition to being physically linked. This study suggests that in the near future, genetic resequencing data of diverse common bean accessions, compiled within an easily accessible database, will facilitate identification of markers for MAS, marker/trait association, and candidate gene identification.

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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Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola and Bean common mosaic and necrosis virus (BCMV/BCMNV) are important diseases of common bean in Tanzania that can cause severe yield reduction when uncontrolled. This study was conducted to incorporate resistant genes for ALS and BCMV/BCMNV diseases into adapted, market class and farmers and consumers preferred bean genotype using marker assisted selection. The parents Mexico 54 and UBR(25)95 donor of Phg-2 and I/bc-3 genes for ALS and BCMV/BCMNV, respectively were used for the recipient being Kablanketi. In selection, SCAR markers SNO2, ROC11 and SW13 linked to Phg-2, bc-3 and I gene, respectively were used. A parallel backcrossing (modified double cross) procedure was used. The F 1 , F 2 and backcrosses from single crosses were characterized. The Chi square values for ALS were 0.081 (P<0.776) and 0.017 (P<0.896) and for BCMNV were 1.609 (P<0.205) and 1.2 (P<0.273) for molecular and phenotypic screening, respectively. The resistance to ALS and BCMNV was found to be monogenic and the genes involved are dominant and recessive, respectively. The heritability of ALS was found to be high (0.772) implying that selection for ALS can be done early in segregating populations. High correlation values, r = 0.741 and 0.624 for ALS and BCMNV, were obtained between phenotypic and molecular data, indicating high reliability for markers. In selection, it was possible to select lines with multiple disease resistances. This work signified the use of MAS for multiple gene screening.

Angular leaf spot disease (ALS) caused byPseudocercospora griseola is one of the most important bean diseases in Tanzania. The bean landraces Beti-10, Nanka, Nanavala and Nkanamna used in this study have been identified as resistant to ALS but the nature of inheritance and mechanisms of resistance against ALS in those potential sources has not been elucidated. This information is crucial and a necessary first step for a successful breeding programme. The objective of this work was to study the inheritance of ALS resistance in those landraces and to identify the mechanisms of genetic resistance using Simple Sequence Repeat (SSR) markers. Crosses were made between resistant bean landraces and a susceptible bean cv Kablanketi. The parents, F 1 , F 2 and backcrosses derived plants were used for inheritance studies and for molecular marker screening using 30 SSR markers. Results indicate that, a single dominant gene control resistance against ALS in each of the four landraces; also the SSR marker Pv-ag004 was found to be polymorphic between Beti-10 and Kablanketi and linked to the disease resistance. The resistance were validated by checking the F 2 population of the cross between Kablanketi × Beti-10. Therefore, since marker Pv-ag004 is polymorphic and linked to ALS resistance, the Beti-10 landrace might be a potential source of ALS resistance. However, a detailed study with more markers need to be done on these landraces with a view to opening the possibilities of identifying new markers linked to ALS resistance and mapping of genes associated with resistance to ALS.

The agricultural sector is challenged to fulfill the nutritional requirements of ever-increasing population. Rates of growth in crop productivity have declined, among many reasons is due to climate change and the decline of water and land resources. Dependence by 50% on few cereal crops like wheat, maize and rice for total food intake and calorie requirements has countersigned loss of biodiversity and decline in crop productivity. The genetic diversity of traditional crop varieties offers resilience to environmental risks, socioeconomic shocks, adaptation and mitigation to climate change which is crucial for crop production. Traditional African Vegetables (TAVs) are an integral constituent of the diets of many rural and urban communities. They are important sources of essential macro and micro-nutrients. In addition, they offer a source of livelihood when marketed, and also contribute to crop biodiversity. Tanzania needs to conserve the Traditional African vegetables and their genetic resources against stressful conditions and increased selection pressures which causes loss of genetic variation and a decrease in fitness by a process called genetic erosion. Conservation and use alleviate genetic drift and inbreeding depression, then, is critical to guarantee TAVs persistence in rural areas. This review explores agrobiodiversity of traditional African vegetables (TAV) from livelihood of Tanzanian rural communities’ perspectives and how the country has managed to conserve these species.