Tagging of cassava mosaic disease resistance gene in cassava (Manihot esculenta Crantz) using simple sequence repeat (SSR) markers

Cassava mosaic disease (CMD) is a major viral disease that causes severe yield loss in cassava cultivation in India. The host plant resistance breeding for CMD is the important strategy to control the disease spread. To understand the nature of disease resistance and identification of simple sequence repeat (SSR) markers closely associated with CMD resistance is important. To study the nature of resistance, seedling and clonal population developed by crossing Sree Jaya (Susceptible) and 9S127 (Resistant) and self-pollinating 9S127 parent were done and the population was evaluated for CMD disease scoring (1-5 scale) at 5 and 8 months after planting. The disease segregate in 1:1 ratio in the F1 and C1F1generation of Sree Jaya × 9S127 cross and 3:1 in the S1, C1S1 self-pollinated progenies of 9S127 parent. It confirms the gene in the resistant parent is heterozygous (Rr) and single dominant gene (RR) is controlling the resistance. In this mapping population, Sri Lankan Cassava Mosaic Virus (SLCMV) is prevalent in all the samples. A total of 14 CMD associated SSR markers were screened in the progenies using bulk segregant analysis (BSA) method. Out of 14 markers, two markers SSRY28, NS158 co-segregate with CMD resistance in the population. These markers can be used for marker assisted selection (MAS) for CMD screening in the seedling population to identify true resistant lines for further breeding trials.