Division of Genetics, Indian Agricultural Research Institute, Delhi-12
*Proceedings of 22nd Annual Conference of Indian Society of Agricultural Statistics, Patna, Feb., 1968.
The stability of performance of some high yielding improved varieties and hybrid derivatives representing the indica and japonica races of rice was examined to detect the genetic differences among them for wide adaptability over a number of locations and two fertility levels during rabi and kharif seasons from 1965–67. Stability was measured in terms of three parameters, viz., phenotypic index (P), phenotypic stability (b) and deviations from linearity (σ2). Phenotypic index, a new term, has been substituted for mean in Eberhart and Russell's (1966) model.
The study has demonstrated that before the advent of IR varieties in India, (T(N)l was most stable over a wide range of environments with highest P, b around 1.0 and σ2 small. But during post-IR era, IR-8, IR-4 and IR-5, in that order, were the best derivatives well adapted to all conditions. The stability of performance has been summarised as follows: Dwarf IR series > Dwarf indicas (Taiwan) >Japonicas>Tall indicas
The study has further brought out the fact that seasonal fluctuations and differential fertility levels could alter the degree of adaptation. In general, dwarf indicas (including IR series) were generally adapted to all conditions during rabi seasons while japonicas were best under kharif seasons, particularly at high fertility levels. The tall indicas were poorly adapted to all conditions with P < 0, b < l.0 and σ2=small.
Differences in stability among the dwarf indicas and japonicas were found indicating the influence of factors other than height on stability. The factors responsible for wide adaptation and choice of the area of adaptation has been discussed.
