Indian Agricultural Research Institute, New Delhi-12
**Present Address: Department of Plant Breeding, Punjab Agricultural University, Ludhiana.
*A part of the thesis submitted by M. M. VERMA for Ph.D. degree of the Indian Agricultural Research Institute, New Delhi.
Regression analysis of developmental characters and yield in soybean has revealed that stablity for primary branches, height, maturity and pod number and plasticity for the period flowering to maturity are the main components of stability for yield.
Grouping of varieties into homogenous groups on the basis of deviations from the linear regression has revealed the predominance of non-linear nature of genotype × environment interaction for almost all the characters which may be responsible for the limited adaptation of this crop. The magnitude of the interaction was the highest for yield, specific gravity of seed and synchrony of maturity, the characters manifested in the late growth phase. The interactions are considerable for characters concerned with early growth phase like early vigour and synchrony of flowering. Selection for stability of developmental traits is suggested to minimise the interactions for yield since the instability of yield and developmental traits is found to be related. High interaction for the period from flowering to maturity appear to be an adaptive mechanism.
Asynchrony of flowering is a compensatory mechanism in soybean and dose not seem to be a disadvantage.
