Screening of proso millet (Panicum miliaceum L.) genotypes for heat tolerance using heat susceptibility index under staggered sowing conditions

Abstract

Heat stress is a major constraint to proso millet (Panicum miliaceum L.) productivity, especially in late sowing, where high temperatures during reproductive stages reduce yield and grain quality. Although proso millet is relatively hardy, genetic variability for thermo-tolerance remains underutilized in breeding. A field study was conducted to screen 22 proso millet (Panicum miliaceum L.) genotypes for heat tolerance using Heat Susceptibility Index (HSI) and morpho-physiological traits during kharif 2024 at PGI Farm Baramati, Maharashtra. Sowing was done on three dates (D₁: 14 August, D₂: 5 September, D₃: 27 September) to impose differential heat stress. Observations on phenological, morphological, physiological, and yield traits were recorded, and HSI was computed to assess genotypic tolerance. Genotypes PRO 705, PRO 750, PRO 681, PRO 693, PRO 452, and PRO 792 exhibited low HSI values across key traits such as days to 50% flowering (no.), days to maturity (no.), grain yield/ plant (g), 1000 grain weight (g), canopy temperature depression (℃) and proline content (µg/g FW) indicating superior thermo-tolerance and yield stability. PRO 705 consistently outperformed checks and other genotypes under all sowing conditions. In contrast, PRO 694, PRO 673, PRO 667, PRO 737, PRO 741, and PRO 790 were identified as heat-susceptible. PRO TNAU 202 showed better tolerance than DHPM 2769.The study identified promising heat-tolerant genotypes, particularly PRO 705, suitable for breeding programs targeting thermo-resilience in proso millet.