Mapping of easy to screen SSR markers for selection of RFLP markers-bracketed downy mildew resistance QTLs in pearl millet

Downy mildew (DM) of pearl millet, caused by fungus Sclerospora graminicola, is the most destructive disease of pearl millet which can cause grain yield losses up to 60%. Also referred to as ‘green ear’, this disease is widely distributed in temperate and tropical areas of the world and is especially important in India and Africa. In an earlier study, quantitative trait loci (QTL) for resistance to Sclerospora graminicola have been reported on linkage groups (LG) 1 and 4 using a F ₂ population derived from the cross of H 77/833–2 and ICMP 451. However, these QTLs were bracketed with labour-intensive restriction fragment length polymorphism (RFLP) markers, thus hampering their use in marker-assisted selection (MAS). The current study reported confirmation of these QTLs using the same cross and phenotypic data generated using seven different pathogen isolates obtained from Africa and India and saturation of the identified genomic regions with easy to screen simple sequence repeat (SSR) markers. The inclusion of SSR markers resulted in a map covering 101.1 cM and 91.4 cM on LG 1 and LG 4 respectively. QTL likelihood maps developed for each of seven Sclerospora graminicola isolates revealed that for most of the isolates, QTLs for DM resistance (DMR) were located either on LG 1 or LG 4, while Niger isolate had QTLs on both the linkage groups and no QTL was located for Mysore isolate. The SSRs can be efficiently utilized in MAS programmes targeting improvement of elite cultivars of pearl millet against this disease.