Research Projects

Soybean (Glycine max L. Merrill) is one of the most important oilseed crops for India, contributing significantly to edible oil and protein production. However, soybean rust caused by Phakopsora pachyrhizi remains a major constraint to productivity, with yield losses reported up to 80% under favorable conditions (Sarbhoy and Pal, 1997; Rosa et al., 2015). In India, rust has emerged as a recurring threat, particularly in major soybean-growing regions like Karnataka, Maharashtra, Manipur, Nagaland, and Meghalaya. Past breeding efforts using resistant donor lines EC 241778 and EC 241780 resulted in the release of rust-resistant cultivars such as DSb21, DSb23, and DSb34 (Patil et al., 2004; Basavaraja et al., 2012). However, recent reports indicate a significant reduction in resistance levels, largely due to evolving pathogen populations and the emergence of new rust pathotypes. The soybean line PI 200487, known to carry resistant alleles at Rpp3 and Rpp5 loci (Yamanaka et al., 2023). Preliminary screening showed that the line PI 200487 has shown reduced percent disease index of 18.52% (77.78% in DSb23), sporulation of 0.83 × 10⁴/ml (7.67 × 10⁴/ml in DSb23), an average of 2.23 uredinia per lesion (12.23 in DSb23), and a lesion density of 36.33 per cm² (116 per cm² in DSb23) to prevalent pathotypes under hotspot conditions at Dharwad. Pyramiding these loci with existing Rpp1b and Rpp2 genes present in DSb23 offers a promising strategy for developing soybean varieties with broad-spectrum, durable rust resistance. This project proposes to: 1. To introgress Rpp3 and Rpp5 loci into DSb23 and development of segregating population 2. To identify rust resistant segregants based on rust phenotyping and marker-assisted selection in F2 generation 3. To advance and evaluate segregating generations for rust resistance The novelty lies in utilizing the line PI 200487, donor of Rpp3 and Rpp5. The strategy integrates field phenotyping under hotspot conditions with MAS for efficient identification of resistant segregants. Rapid generation advancement (two generations/year) will ensure rapid generation advancement to develop durable, broad-spectrum rust-resistant lines. Expected outcomes include the development of resistant soybean lines with enhanced durability, reduced production costs for farmers, improved yield stability, and lower reliance on fungicides. The project supports national priorities of increasing oilseed self-sufficiency, enhancing farmer income, and promoting environmentally sustainable agriculture. The project will also register improved breeding lines with NBPGR, ensuring genetic conservation and future breeding use. Therefore, through integration of conventional breeding, MAS, and field validation in rust hotspot locations, this proposed project offers efficient and environmentally safe way to manage soybean rust disease through development of durable resistance, thus strengthening India's soybean sector and contributing to national edible oil security.