Abstract
Soybean is an important oilseed cum vegetable crop, susceptible to various biotic stresses which is attributed to recent decline in crop productivity. The emergence of virulent biotypes/strains of different plant pathogens necessitates the development of new crop varieties with enhanced host resistance mechanisms. Pyramiding of multiple disease-resistant genes is one of the strategies employed to develop durable disease-resistant cultivars to the prevailing and emerging biotypes of pathogens. The present study, reports the successful introgression of two major R-genes, including Rps2 (Phytophthora rot resistance), Rmd-c (complete-powdery mildew resistance) and effective nodulating gene (rj2) through functional Marker-Assisted Backcross Breeding (MABB) in the genetic background of well-adapted and high yielding soybean varieties, CO 3 and JS 335. We have identified several promising introgressed lines with enhanced resistance to Phytophthora rot and powdery mildew. The improved soybean lines have exhibited medium to high level of resistance against powdery mildew and Phytophthora rot as well as displayed effective nodulation capacity. Our study has proven the generation of resistant genotypes to realize the potential of MABB for achieving host plant resistance in soybean. The improved lines developed can greatly assist the soybean breeding programs in India and other soybean growing countries for evolving disease-resistant varieties.
Highlights
Phytophthora root and stem rot and powdery mildew are the widespread diseases of soybean crop affecting all major plant parts including seeds, stems, leaves, and roots
Polymerase Chain Reaction (PCR)-based markers developed based on BAC end sequences, and linked SSR markers with Rps2/Rmd-c/rj[2] gene in the J linkage group were tested for polymorphism
Parental polymorphism survey through molecular markers revealed the distinct banding pattern of the genes/alleles to be introgressed into susceptible recipient parent, i.e., CO 3 and JS 335 from resistant donor parent, i.e., CNS (91F11L: Rps2 + Rj2 + Rmd-c) (Fig. 2)
Summary
Phytophthora root and stem rot and powdery mildew are the widespread diseases of soybean crop affecting all major plant parts including seeds, stems, leaves, and roots. CNS is the source of resistance to powdery mildew disease and controlled by a single allele (Rmd-c), was shown to offer resistance throughout the entire life cycle of p lant[14] Another gene, RpsUN2 different from Rps[2] was mapped in this region and is located approximately 0.8 cM downstream of Rj2, and the genetic distance between RpsUN2 and Rps[2] is between 3.0 and 3.4 cM15. Development of well-adapted Phytophthora rot and powdery mildew resistant cultivars as well as with effective nodulation ability may offer a source material for the soybean breeding program in India and elsewhere
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