Microsatellite-based association mapping for agronomic traits in mungbean (Vigna radiata L. Wilczek).

Mungbean (Vigna radiata L. Wilczek) is one of the most important warm season food legumes which contributes significantly towards nutritional security and environmental sustainability. Marker-trait association (MTA) for agronomic characters offer opportunities to deploy marker-assisted breeding for genetic amelioration of crops. This investigation was carried out with an objective to decipher population genetic structure of diverse Vigna accessions and detect microsatellite loci linked to major agronomic traits for mungbean improvement. The study was initiated with 290 diverse Vigna accessions including wild and cultivated accessions. A mungbean yellow mosaic India virus (MYMIV)-resistant association mapping panel was constructed to minimize the effect of yellow mosaic disease on crop performance. Among these, 117 accessions including 55 cultivated and 63 wild accessions were found highly resistant to MYMIV. After multi-environment phenotyping, a panel of 70 MYMIV-resistant mungbean accessions was subjected to analysis for assessing the population genetic structure as well as MTA for important agronomic traits. There was sufficient genetic variation among the 70-mungbean genotypes as depicted by 91 microsatellite markers. Population genetic structure analysis grouped the genotypes into five subpopulations. The locus GMES0162 (LG4) was strongly associated with days to first flowering, whereas loci CEDG 035 (LG8), DMB SSR001 (LG6), DMB SSR008 (LG4) and CEDG 168 (LG11) were associated with pod number. These marker-trait associations will be helpful in genetic improvement of mungbean through molecular breeding.

Marker-assisted introgression of resistance to fusarium wilt race 2 in Pusa 256, an elite cultivar of desi chickpea.

Fusarium wilt caused by F. oxysporum f. sp. ciceris causes extensive damage to chickpea (Cicer arietinum L.) in many parts of the world. In the central part of India, pathogen race 2 (Foc 2) causes severe yield losses. We initiated molecular marker-assisted backcrossing (MABC) using desi cultivar, Vijay, as a donor to introgress resistance to this race (Foc2) in Pusa 256, another elite desi cultivar of chickpea. To confirm introgression of resistance for this race, foreground selection was undertaken using two SSR markers (TA 37 and TA110), with background selection to observe the recovery of recurrent parent genome using 45 SSRs accommodated in 8 multiplexes. F1 plants were confirmed with molecular markers and backcrossed with Pusa 256, followed by cycles of foreground and background selection at each stage to generate 161 plants in BC3F2 during the period 2009-2013. Similarly, 46 BC3F1 plants were also generated in another set during the same period. On the basis of foreground selection, 46 plants were found homozygotes in BC3F2. Among them, 17 plants recorded >91% background recovery with the highest recovery percentage of 96%. In BC3F1 also, 14 hybrid plants recorded a background recovery of >85% with the highest background recovery percentage of >94%. The identified plants were selfed to obtain 1341 BC3F3 and 2198 BC3F2 seeds which were screened phenotypically for resistance to fusarium wilt (race 2) besides doing marker analysis. Finally, 17 BC3F4 and 11 BC3F3 lines were obtained which led to identification of 5 highly resistant lines of Pusa 256 with Foc 2 gene introgressed in them. Development of these lines will help in horizontal as well as vertical expansion of chickpea in central part of India.