Molecular Marker-Assisted Backcrossing of Anthracnose Resistance Genes into Common Beans (<i>Phaseolus vulgaris</i> L.) Varieties

Abstract

Anthracnose, caused by Colletotrichum lindemuthianum , is a major disease of common bean and results in high yield loss. Due to the high degree of pathogenic variability of the fungus and the continual emergence of new races, genetic resistance in the host is not durable. Gene pyramiding using Marker Assisted Selection (MAS) is proposed as a viable approach to improve the durability of major genes conditioning resistance to anthracnose. In this study a common bean line Urugezi x AND 1062 susceptible to anthracnose but already improved for Pythium root rot resistance was improved for anthracnose resistance through a backcross breeding program. Genotypic selection was done in Rubilizi laboratory in Kigali, Rwanada whereas phenotypic selection was conducted in an anthracnose hotspot at Rwerere, a research Centre of the Rwanda Agricultural and Animal Resources Development Board (RAB). Analysis of variance for effect of bean varieties and anthracnose isolates on disease expression showed significant differences (p < 0.001) among varieties and isolates and for the interaction between isolates and varieties. Developed BC 2 F 1 plants were 41% of them resistant and 59% susceptible to anthracnose. However, the observed proportion of 26 resistants and 37 susceptible in BC 2 F 1 plants didn’t fit the goodness of fit of the expected proportion of 75 resistants to 25 susceptible. Only 41% of BC 2 F 1 plants inherited the resistance genes and were phenotypically resistant. Presence of SCAR-markers, SAB3 and SBB14, in the developed resistant lines h suggested successful resistance transfer of anthracnose resistance genes.