Indian Agricultural Research Institute, New Delhi
*Present Address: Deptt. of Plant Breeding and Genetics, Orissa University of Agriculture and Technology, Bhubaneswar-3.
Nature of gene action and heterosis for maturity characters, yield and yield components and developmental traits like chlorophyll depth and synchrony of development in brown sarson were analysed through estimates of gene effects from generation means of five intervarietal crosses.
Both additive and non-additive gene action were found to be important for all the characters. Epistatic effects were predominant over additive and dominance effects with an important role of duplicate epistasis for several characters. However, specific crosses exhibited significant fixable effects for days to flowering and maturity, plant height, primary branches, siliqua length, seeds/siliqua and yield indicating that selection in segregating genertions would be effective for these characters.
The nature of gene action for the developmental traits was similar to those for yield and its components except that the additive effect appeared to be of greater importance for the former than it is for the latter characters.
Heterosis was either absent or low for most of the characters in all the crosses. The low heterosis was mainly due to internal cancellation of the gene effect components. The presence of marked non-additive gene action points to the need for exploiting both the fixable and non-fixable components of genetic variation in breeding for productivity in this crop.
