Marker-assisted introgression lines of elite Indian mustard (Brassica juncea) cultivars for resistance against white rust (Albugo candida)

White rust caused by Albugo candida is a major biotic constraint responsible for significant yield loss in mustard production across all mustard-growing regions. This experiment was conducted with the aim of developing WRR lines of Indian mustard using the MABB approach. The elite mustard cultivars of Brassica juncea viz., DRMR150-35, DRMRIJ-31 and NRCDR-02 were used as the recurrent parent, whereas BioYSR, BEC-144 and Donskaja were taken as donors. A parental polymorphism survey using 315 microsatellites (SSR) was done among recurrent and donor parents. To confirm introgression of white rust resistance gene foreground selection was performed using Arabidopsis-derived IP markers that are linked to the white rust loci AcB1-A5.1 (At2g36360) for Donskaja and Bio YSR and AcB1- A4.1 (At5g41560) for BEC-144 coupled with background selection and phenotypic selection for highest recurrent parent genome recovery. Finally, 19 BC₃F₃ lines were obtained, which led to the identification of 5 highly white rust-resistant lines with RPG recovery percentage of >90%. These selected improved lines showed a resistance response with mean %WR severity (100 DAS) below 5% and possess the agro-morphological characters at par to their respective recurrent parent. These lines have good potential for future release and demonstrated MABB as a valuable tool for expediency, enrichment and precision in accelerating the development of new disease- resistant Indian mustard varieties.