INTERGENERIC HYBRIDIZATION BETWEEN BRASSICA OLERACEA AND ERUCA SATIVA

Intergeneric sexual hybrids have been generated between Brassica oleracea (2n = 18, CC) and Eruca sativa (2n = 22, EE). Aim of the project was the combination of the Eruca sativa nuclear genome with the CMS inducing Ogura-cytoplasm of a cauliflower breeding line. The F₁ plants obtained showed an intermediary phenotype, an almost normal growth habit, expressed male sterility, but no seed set after pollination with the Eruca parent. Chromosome doubling of F₁ plants by colchicine treatment resulted in five allotetraploid plants (CCEE). Backcrosses with the E. sativa parent supported by embryo rescue resulted in BC₁ plants, which resembled more or less the Eruca phenotype and were completely male sterile. Repeated backcrosses with E. sativa pollen resulted in BC₂ and BC₃ progenies.
The hybrid status of the F₁ and the elimination of B. oleracea chromosomes were checked by RAPD-PCR, flow cytometry and GISH analysis. Mitochondrial DNA was tested by Southern hybridization confirming maternal inheritance. Flower-biological and flower-histological investigations were carried out for each backcross progeny. BC₃ plants, containing exactly the expected 2_n = 22 chromosomes of E. sativa, expressed a highly vigorous phenotype and stable male sterility as prerequisite for successful application in Eruca hybrid breeding.