DEVELOPMENT OF STRESS TOLERANT VERSIONS OF POPULAR RABI SORGHUM VARIETIES USING BACKCROSS BREEDING APPROACH

Abstract

Rabi sorghum (Sorghum bicolor (L.) Moench) is an important food and fodder crop cultivated under the post-rainy season in the semi-arid regions of India, where productivity is frequently constrained by major biotic and abiotic stresses. The present investigation aimed to develop stress-tolerant versions of popular rabi sorghum cultivars through conventional backcross breeding by introgressing resistance to stem borer, aphid, shoot bug, rust and terminal drought, and to evaluate advanced BC₂F₄ backcross-derived lines for agronomic performance, physiological efficiency and stress tolerance. Nineteen BC₂F₄ backcross-derived lines, developed using six elite recurrent parents and seven trait specific donor parents, were evaluated during Rabi 2024–25 at the Centre on Rabi Sorghum, ICAR–Indian Institute of Millets Research, Solapur, in a randomized complete block design with three replications. Advanced backcross derived lines were further screened for stem borer resistance across four hotspot locations, rust resistance under natural epiphytotic conditions and terminal drought tolerance using a gravimetric lysimeter facility at ICAR–IIMR, Hyderabad. Significant genetic variability was observed among the BC₂F₄ lines for agronomic and physiological traits. Field evaluation identified BC2F4-4 {(BJV-44 × SLR-31) × BJV-44} as the best-performing genotype, recording the highest grain yield (57.93 g plant⁻¹), panicle weight (73.40 g), harvest index (54.92%) and SPAD value (67.68). Likewise, BC2F4-14 {(SPV-2217 × SLR-10) × SPV-2217} and BC2F4-15 {(CSV-29R × SLR-10) × CSV-29R} exhibited superior grain yield and desirable agronomic performance, whereas BC2F4-18 {(Parbhani Jyoti × RNTN 13-37) × Parbhani Jyoti}, BC2F4-12 {(SPV-2217 × RSV-2121) × SPV-2217} and BC2F4-19 {(BJV-44 × RNTN-13 37) × BJV-44} showed improved physiological performance with higher relative water content and chlorophyll retention. Multi-environment screening further validated the breeding programme, with S24007RV and S24005RV exhibiting superior stem borer resistance, S24009RV and S24010RV expressing stable rust resistance, and S24003RV recording the highest transpiration efficiency (10.84), total water use (13.24 kg plant⁻¹) and grain yield under drought stress (70.25 g plant⁻¹). The study demonstrated that conventional backcross breeding effectively combined superior agronomic performance with resistance to major biotic and abiotic stresses, resulting in elite BC₂F₄ introgression lines that constitute valuable genetic resources for developing high-yielding, climate-resilient rabi sorghum cultivars adapted to post-rainy season environments.