Expression of residual heterosis in f₂ and f₃ generations of soybean (Glycine max L.) for yield and agronomic traits

Soybean (Glycine max L. Merrill) is a vital legume crop valued for its protein-rich seeds and oil content. While heterosis is commonly exploited in cross-pollinated crops, its potential particularly residual heterosis in self-pollinated species like soybean is increasingly recognized. This research aimed to quantify and evaluate residual heterosis in F₂ and F₃ generations derived from twenty-one diverse soybean crosses, developed by line x tester analysis. This study was conducted to evaluate the extent of residual heterosis in the F₂ and F₃ generations of soybean under field conditions at Norman E. Borlaug Crop Research Centre, G. B. Pant University of Agriculture and Technology, Pantnagar for seed yield per plant during kharif season. The experimental material consisted of 21 crosses, 7 lines, 3 testers and 1 check and their corresponding F₃ progenies developed. The experiment was laid out in a randomized complete block design (RCBD) with two replications. Observations were recorded on key agronomic and yield-related traits. For seed yield per plant, the standard parent residual heterosis values varied from-51.67 to 50.12 and-54.56 to-27.58, respectively. Only one F2 cross, PK1029XJS335, demonstrated significant positive residual heterosis over mid parent, better parent, and standard parent for seed yield per plant, while three F2 crosses, PK1029 x JS335, PK1029 x PS1225, and PS1042 x PS1225, out of 21 crosses, demonstrated significant positive residual heterosis. None of the 21 F3 crosses displayed significant positive residual heterosis over the standard parent, but 13 crosses demonstrated substantial positive residual heterosis over the mid parent and seven crosses over the better parent.