Cytogenetic and molecular characterization of intergeneric hybrids between Brassica napus and Orychophragmus...

Twenty-two intergeneric hybrids from a cross between Brassica napus (AACC, 2n = 38) cultivar Oro and the ornamental crucifer Orychophragmus violaceus (OO, 2n = 24) were produced without embryo rescue. The plants were classified into three groups based on morphological and cytological observations and RAPD banding patterns. Plants of Group I had morphological traits of both parents and 2n = 29 chromosomes. In these plants, 62.1% of the pollen mother cells (PMCs) had the pairing configuration 1 III + 9 II + 8 I; the remaining PMCs had 10 II + 9 I. The plants possessed 97.6-98.8% B. napus specific and 9.2-11.7% O. violaceus specific RAPD fragments. Plants of Group II exhibited novel morphological traits and possessed 2n = 35, 36, or 37 chromosomes. Plants of Group III were morphologically similar to B. napus and possessed 2n = 19, 37, 38, or 39 chromosomes. Plants of Group II and Group III had 94.1-99.4% B. napus specific RAPD fragments and no O. violaceus specific RAPD fragments. Chromosome fragments were observed in PMCs of most of the F1 plants in all groups. Based on the cytological results and RAPD analysis, it is suggested that genome doubling and chromosome elimination occurred in the intergeneric hybrids of B. napus x O. violaceus.