Germplasm diversity and heterosis in oilseed rape (Brassica napus L.)

摘要

With the success of Ogu-INRA CMS system, the focus of breeding efforts in oilseed rape has shifted decisively towards hybrid breeding. Delineation of germplasm into heterotic gene pools is important as complementation between divergent parents is known to define limits of heterosis. In this communication we present results of our attempts to measure genetic diversity in Indian and Australian B. napus germplasm (36) on the basis of variation for twelve morphophysiological traits. Diversity analysis (UPGMA) categorized the test germplasm into five groups with overall dissimilarity coefficient of 0.59 suggesting a narrow genetic base. Group Ⅰ comprised 13 Australian genotypes with dissimilarity coefficient of 0.30. Group Ⅱ comprised seven Australian canola, six Indian canola and two Indian non-canola types. Two Australian (Monty and BST-7-2M2) and one Indian non-canola type were included in Group Ⅲ. Trilogy was the lone genotype in Group Ⅳ, close to Group Ⅴ comprising two Indian canola types GSC 302 and OCN 3, besides an Australian genotype Tranby. Based on genetic diversity, three sets of hybrids (95) were developed by crossing selected Australian lines as female with Canadian (Ashai), Indian canola (OCN 3 and GSC 5) and Indian non-canola (GSL 1 and Neelam) cultivars as males. These hybrids were evaluated against GSC 5 as a frequent check to estimate standard heterosis. Average heterosis in these three sets respectively, was 0.6, 19.8 and 37.5 per cent, suggesting, in general, an association of standard heterosis with diversity in the test germplasm evaluated. Two canola (Rivette×OCN 3 and AvSapphire×GSC 5), and six canola×non-canola combinations (AG-Spectrum×GSL 1, Oscar×Neelam, AV-Sapphire×GSL 1,Surpass 400×Neelam, Monty×Neelam and Oscar×GSL 1) were highly productive.