Improvement of rapeseed (Brassica napus L.) for agronomic and quality characters through induced mutations and hybridization

Mutation breeding research of oilseed rape (Brassica napus L.) with the objective to develop improved varieties characterized by having high yield potential, high oil content of better quality, and resistance/tolerance to different stresses was initiated during 1988 - 89. Based on GR50 dose, bold and uniform seeds with 10 - 12 % moisture of different rapeseed varieties/lines were subjected to 800, 1,000 and 1,200 Gy 60Co gamma radiation and treated with 1.0, 1.5 or 2% ethyl methanesulphonate (EMS) and 1X10-4, 1x10-3, 1x10-2 M sodium azide (NaN3) solutions for four hours. The treated seeds were directly sown in the field in isolation as M1. Selection of desirable mutant plants was made in M2 - M3. The stable progenies were evaluated in microplot tests in M5 and M6, for yield potential and other agronomic and quality characters in comparison with respective parent and a local commercial cultivar as checks. Results of yield trials indicated significant variability with regards to grain yield. A number of mutants expressed high yield potential and many had significantly outyielded both the checks. Plant height was reduced in certain mutants but reduction to an ideal level could not be induced. Variability in physiological maturity was also noted and four mutants matured significantly earlier than the checks by a margin of three weeks. Yield tests under drought conditions revealed that 16 out of 28 mutants of cv. Pak-Cheen and Tower significantly outyielded the checks. As a result of significant increase in seed size, total oil content was also enhanced in many mutants and the highest oil content (50%) was observed in mutant line RM-13-1. Quality analysis indicated that 15 mutants produced oil of Canola quality. Cross breeding of promising mutant lines with exotic Canola quality lines was started during 1990 - 91. So far, the F2 generation has been raised and 102 recombinants with desired plant attributes have been selected. 19 refs, 8 tabs