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Cytomorphology of Brassica napus × B. rapa hybrids and patterns of variation in the F2 derivatives

Choudhary, Bagada Ram, Joshi, Purushottam
Caryologia 2012 v.65 no.4 pp. 316-321
Brassica napus, Brassica rapa subsp. dichotoma, Brassica rapa subsp. trilocularis, chromosomes, crossing, females, genetic variation, genome, hybrids, meiosis, metaphase, parents, pollen, transgressive segregation
The present study was carried out to determine crossability between Brassica napus and B. rapa , to elucidate chromosome homoeology between different Brassica genomes in the F ₁ hybrids and to estimate genetic variability in F ₂ progenies of the crosses. Crosses between B. napus (AACC, 2 n = 38) and B. rapa (AA, 2 n = 20) vars. brown sarson , yellow sarson and toria were attempted and the hybrid derivatives were advanced to F ₂ generation. Hybrid recoveries were higher when B. napus was used as a female parent. The F ₁ plants were luxuriant in growth and intermediate to their progenitor parents for morphological attributes. The meiotic studies of F ₁ plants (AAC, 2 n = 29) showed 10 bivalents in the majority of pollen mother cells analyzed. A maximum of 12 II was found in a few cells. The occurrence of multivalent associations as trivalent and quadrivalent at metaphase I, and a bridge-fragment configuration at anaphases were attributed to homoeology between A and C genomes. In the F ₂ generation, a high percentage of plants resembling B. napus were observed. Transgressive segregation in both directions was observed for yield contributing traits.