Improved host-plant resistance to Phytophthora rot and powdery mildew in soybean (Glycine max (L.) Merr.)

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. 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. Many of the high yielding soybean mega-varieties are highly susceptible to both diseases 1-3. Infections by these pathogens cause severe tissue collapse in host plant that negatively impacts plant growth and productivity. Many of the chemical, cultural and biological methods suggested are practically inadequate to combat these diseases successfully 1,4,5. However, a sustainable approach for combating pathogenesis is to introgress the disease resistant (R-genes) and QTL from the identified soybean lines in to cultivars 5. Although many research groups have successfully introgressed R-genes into an elite variety 6,7 through marker-assisted breeding, there are very few reports of utilizing marker-assisted backcross breeding (MABB) method. Successful MABB was reported in soybean for mobilizing the null allele of β-conglycinin α-subunit 8 and Kunitz trypsin inhibitor 9. Following this example, it will be valuable to introgress the R-gene(s) through MABB to achieve high recurrent parent genome recovery (RPG) while eliminating the linkage-drag effect on target chromosome(s).

Genome-wide association study, haplotype analysis, and genomic prediction reveal the genetic basis of yield-related traits in soybean (Glycine max L.)

“…This classification assisted in the use of these alleles for yield modulation in soybean. To date, the effectiveness of marker-based gene pyramiding strategies in soybean has been demonstrated for soybean mosaic virus ( Wang D. G. et al, 2017 ), Phytophthora rot and powdery mildew resistance ( Ramalingam et al, 2020 ), and rust resistance ( Yamanaka and Hossain, 2019 ). Hence, the elite alleles identified for yield-related traits within six significant SNP markers can be effectively used for developing high-yielding soybean varieties through MAB efforts.…”

Genetic Augmentation of Legume Crops Using Genomic Resources and Genotyping Platforms for Nutritional Food Security

“…Cyst nematode resistant genotypes of soybean have been developed by stacking resistance alleles, from wild to the cultivated varieties of soybean, using MAS and MARC methods [ 141 ]. Ramalingam et al [ 145 ] improved the host-plant resistance to Phytophthora rot and powdery mildew in soybean by the introgression of resistance genes Rps2 ( Phytophthora rot resistance) and Rmd-c (powdery mildew resistance), along with a gene ( rj2 ) linked with nodulation. Three soybean mosaic virus resistance genes—namely, RSC4 , RSC8 , and RSC14Q —have been pyramided in soybean through the MABC programme [ 146 ].…”

Progress and prospectus in genetics and genomics of Phytophthora root and stem rot resistance in soybean (Glycine max L.)

“…In Japan, “Hyogo Prefecture,” the black-seeded PRSR-resistant line, was used as the donor for introgression and for the development of resistant cultivars ( Sugimoto et al, 2010 ). Although plant breeders use MAS-based approaches mainly for transferring Rps genes in soybean ( Li et al, 2010 ; Ramalingam et al, 2020 ), due to high disease pressure, rapid evolution in the pathotypes of P. sojae has been witnessed over the past 3 decades, hence making vertical resistance ineffective. This forced the plant breeders to target partial resistance for the effective and sustainable management of PRSR ( Schmitthenner, 1985 ).…”