Soybean (Glycine max L.) is an important edible-oil crop whose productivity faces threats of rising temperature under climate change, making the identification of heat-tolerant genotypes crucial. This study evaluated 18 soybean genotypes for heat tolerance across five temperatures (25 °C, 30 °C, 35 °C, 40 °C, and 45 °C), focusing on survival rate, shoot and root lengths, and total plant weight. Gepak Kuning, Argomulyo, and Demas 1 showed robust resilience and consistent superiority. The highest broad-sense heritability (H² up to 1.00) recorded was for these traits, underscoring their breeding potential. Correlation showed positive associations among root length, shoot length, and leaf area, suggesting these as tolerance indicators. Heat tolerance index (HTI) classified Gepak Kuning, Argomulyo, and Demas 1 as tolerant; Devon 1, Denasa 1, and Derap 1 as moderately tolerant; and Detap 1, Grobogan, and Dering 3 as susceptible. The study identified promising heat-tolerant genotypes and traits for climate-smart soybean breeding.
Soybean (G. max L.), heat stress, early growth stage, heat tolerance index, thermo-tolerance screening
Soybean (G. max L.) genotypes Gepak Kuning, Argomulyo, and Demas 1 revealed significant heat tolerance at 45 °C with the highest survival rate and heat tolerance index. Positive correlation between root-shoot traits enables integrated selection strategies to enhance plant vigor under tropical heat stress conditions.