Identification and Validation of Quantitative Trait Loci of Mungbean Yellow Mosaic Virus Disease Resistance in Blackgram [Vigna mungo (L). Hepper]

Background: Blackgram [Vigna mungo (L.) Hepper] is an important food legume crop of India. Mungbean yellow mosaic virus (MYMV) disease is the major problem in blackgram. The disease can reduce seed yield upto 100% or even kill a plant infected at an early vegetative stage. The most effective way to prevent the occurrence of this disease is to develop genetically resistant cultivars of blackgram. However, a major difficulty in breeding MYMV disease resistant in blackgram is field screening for the virus disease. Hence identification of QTL followed by Marker-assisted selection (MAS) is highly useful for genetic improvement of crops. With this background, a study was made for identification as well as validation of quantitative trait loci (QTL) for MYMV disease resistance in blackgram.Methods: A total of 112 F2:3 lines were evaluated for MYMV disease resistance along with parents viz., MDU 1 (MYMV disease susceptible) and Mash 1008 (MYMV disease resistant) at the National Pulses Research Centre, Tamil Nadu Agricultural University, Vamban, Tamil Nadu during July-September 2018 under Augmented Design in the field. Each line was sown in one row of 3 m in length with a spacing of 30 cm as between row and 10 cm as within row. Susceptible genotypes CO 5 and MDU 1 were sown as disease spreader rows after every eight rows and also around the plots. The MYMV disease score was recorded on 60 DAS, by using phenotype rating scale from 1 (resistant) to 9 (highly susceptible), as suggested by Singh et al. (1995). The mean of each progeny was calculated and used as phenotypic data. A total of 525 SSR primers were used to test polymorphism between parents MDU 1 and Mash 1008. Genotyping was carried out for 112 F2:3 RILs of the cross MDU 1 x Mash 1008 with 35 polymorphic SSR markers. Linkage and QTL analyses were performed using QTL IciMapping (version 4.1.0.0) (Wang et al. 2016) and QGene 4.4.0 (Joehanes and Nelson 2008) respectively. Two mapping populations MDU 1 x Mash 114 and CO 5 x VBN 6 in F2:3 and F2 generations respectively were used in this study to validate the identified QTL regions.Result: QTL study indicated the presence of two major QTLs for MYMV disease score in LG 2 and LG 10 at 60 DAS with 20.90 and 24.90% of phenotypic variation respectively. Validation of these QTLs in two other mapping population indicated that QTL on LG 10 was validated with high phenotypic variation of 45.40-46.00%. Hence it may conclude that qmymv10_60 may be utilized for MAS/ MABC with assured improvement on MYMV disease resistance in blackgram.