Brassica napus (+) B. tournefortii, a somatic hybrid containing traits of agronomic importance for rapeseed breeding

Abstract

Somatic hybrids were produced between hypocotyl protoplasts of Brassica napus (rapeseed) and mesophyll protoplasts of B. tournefortii using protoplast fusion. Fusion products were selected by flow cytometry and cell sorting. Twenty-three plants regenerated from individual calli originating from 4 fusion experiments were successfully transferred to the greenhouse. Nineteen of these were characterized as hybrids according to analysis of morphological characteristics, isoenzyme and nuclear RFLP patterns. Analysis of nuclear DNA content revealed a variation in ploidy level among the hybrids, even though a large number (53%) had a DNA content corresponding to the sum of the parental nuclear DNA. Most of the hybrids were intermediate in morphology between B. napus and B. tournefortii. The flowers displayed a range of variation: from normal flowers to abnormal flowers with reduced number of anthers and petals. Fertility investigation showed that both fertile and sterile hybrids were obtained. Five were self fertile, while 10 were male sterile and 4 were completely sterile. Phoma lingam resistance was transferred from B. tournefortii to the hybrid plants. Out of the 16 hybrids examined 12 showed resistance to P. lingam. Chloroplast DNA (cpDNA) patterns of the hybrids were identified by hybridizing a cpDNA probe to total genomic DNA. Of 18 hybrids analysed, 11 had B. tournefortii and 7 B. napus cpDNA pattern. No recombinant cpDNA banding pattern was found. In contrast to the cpDNA, mitochondrial DNA (mtDNA) rearrangements were detected in the hybrids. Out of 18 analysed hybrids, 7 showed evidence of mitochondrial recombination, while 11 had mtDNA identical to either of the parental types.