Description

A poster presented at the 2012 Global Pulse Researchers Meeting, Kigali, Rwanda- “Transforming Grain-Legume Systems to Enhance Nutrition and Livelihoods”. Abstract: Common bean (Phaseolus vulgaris L.) plays an essential role in sustaining livelihoods of smallholder farmers and their families in Africa but they are attacked by several diseases leading to poor yields. Deploying multiple disease resistant varieties (MDRVs) is probably the cheapest means of managing this problem. The overall objectives of this study is to contribute to the development of MDR varieties through the development of multiple disease resistance parents (MDRPs) by pyramiding of key disease resistance genes in a common background. Molecular markers that are tightly linked to resistance genes allow for indirect selection of resistance and ensure that useful genes are not lost during selection. Molecular markers linked to resistance genes to three fungal and one viral disease were utilized. The genes and sources of resistance used were: the I and bc- 3 genes for Bean Common Mosaic Virus (BCMV) and its necrotic strain Bean Common Mosaic Necrotic Virus (BCMNV) from variety MCM5001; Co-4, Co-5 and Co-7 genes for anthracnose resistance from G2333; Prr gene for Pythium root rot resistance from MLB-49-89A, and the phg gene for angular leaf spot resistance from MEX54. Single crosses between these parents were conducted and screening of up to 1500 F2 plants per cross was done using markers. Plants positive for 2 to 3 gene combinations were selected and double crosses were conducted between plants with differing combinations. Over 3000 plants of the F2 progeny of the double cross are being screened to select at least 500 and a maximum of 800 progeny of the root genotype with a 7-gene combination of I, bc-3, Co-4, Co-5, Co-7, Prr, phg. Currently over 580 F1 seeds of the four parent cross [(MLB-49-89A x MEX 54) x (MCM5001 x G2333)] have been obtained. We aim to use the root genotypes to develop ideotypes with fixed multiple resistance genes that can be utilized by our partners in their national bean breeding programs. Using MDRPs could speed up the process of developing MDRVs as compared to use of single disease resistance sources.