Genotype – Pathogen Characterization And Markers Identification For Angular Leaf Spot Disease Resistance In Common Bean In Tanzania

EXTENDED ABSTRACT

This work aimed at characterizing Angular Leaf Spot (ALS) and Pseudocercospora griseola in relation to its host and characterization of resistant genotypes amongst the locally adapted genotypes. A survey was conducted in nine regions where disease severity was established and samples of pathogen and genotypes collected for variability study based on molecular and pathogenicity characteristics. Resistant genotypes were characterized based on their response to ALS in field and screen house. The inheritance pattern, allelic relationship and maternal influence were elucidated and further, molecular markers linked to ALS disease resistance in the selected genotype were identified. The results showed that, ALS disease is distributed in all bean-growing regions with the highest severity of seven in Mbeya and Kagera, and lowest of four in Manyara and Rukwa. Molecular characterization showed the presence of 69.7% Andean and 30.3% Mesoamerican strains of P. griseola and 84.2% Andean and 15.8% Mesoamerican host genotypes where in both cases Andean gene pool out-numbered Mesoamerican gene pool with Andean genotypes being more susceptible to ALS as compared to Mesoamerican genotypes. In the identification of resistant genotypes, results indicated significant variations (P ≤ 0.01) on the response of different genotypes to the disease. Beti-10 and line RJRILS135 were suggested as potential resistant parents with disease scores not different from the resistant controls Mexico 54 and CAL 143. In characterizing Beti-10, segregation results for F2-Kablanketi/Beti-10 (P = 0.806) and F2-Beti-10/Kablanketi (P = 0.052) indicates that, single dominant gene is responsible for resistance to ALS disease in Beti-10 with no maternal influence. Further there was no allelic relationship between Beti-10 and Mexico 54 which indicates independence of resistant genes in these genotypes. Among the SCAR markers used, PF13(Phg109898) and SN02(Phg-2) were found to be linked to the locus responsible for resistance in Beti-10 in repulsion and coupling phase respectively ii and have 80% and 95% reliability for use in marker assisted selection. In this study, ALS pathogen is reported to be highly variable, genotypes that are resistant to ALS have been identified and characterized and markers linked to disease resistant loci identified of which their use will enhancing ALS resistance