Abstract

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 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 F₁, F₂ 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.

Key words: Common bean, Pseudocercospora griseola, marker assisted selection, genotype, inheritance.