Production And Studies Of Intergeneric Hybrids Between Raphanus Sativus And Brassica Oleracea

The crosses between radish (Raphanus sativus L., 2n=18, RR) and cabbage (Brassica oleracea L., 2n=18, CC) are often applied to transfer useful genes such as OguCMS and various resistance genes against disease and pest from radish to cabbage or rapeseed. In this paper, four R. sativus cultivars and two B. oleracea varieties (B. oleracea var. alboglabra and acephala) were adopted as reciprocal cross parents and genomic in situ hybridization (GISH) was applied for cytogenetic studies of intergeneric hybrids and its progenies. The main results and conclusions were as follows:1. 361 hybrid plants including 10 crosses were obtained from the seeds and rescue embryo after hand pollination. It was found that the hybrids were produced with more difficulty when B. oleracea useed as the female than as the male parent. Pollen grain germination and pollen tube growth were investigated in these hybridizations. In the combination of R. sativus×B. oleracea, the misogamy occurred before spermatization, few cabbage pollen grains could germinate on the radish stigma, but the hybrid embryos were more easiey developed on the plants than on medium once germination happened. In the combination of B. oleracea×R. sativus, radish pollen grains were compatible to the cabbage pistil, and the hybrid embryos were hardly developed on maternal plants and should be rescued by ovary or embryo culture.2. The hybrids were morphologically intermediate between their parents, the somatic cells had 18 chromosomes as expected; DNA fingerprinting of simple sequence repeat (SSR) analysis showed the nuclei DNA of intermediate plants had fingerprint of both parents.3. The somatic cells of hybrids had the expected chromosomes (2n=18, RC ), but the pollen mother cells (PMCs) had different chromosome numbers. Three types of PMCs were observed. (1)2n=18, RC. The average pairing pattern was 14.87 I +1.20 II +0.04III +0.06IV. GISH analysis indicated that most bivalents consisted of radish and cabbage chromosomes, and the nine radish chromosomes separated mainly as 5/4 and 6/3 at anaphase I , so the chromosome components in gametes were not equilibrium and the gametes were sterile. (2)2n=36, RRCC. The chromosomes paired and separated normally, producing gametes with RC components . (3)2n=30-34, nullisomic of RRCC. GISH showed some radish chromosomes were lost, and its gametes had nine cabbage chromosomes and partial radish chromosomes.4. The progenies of F₁ were reproduced via duplication with colchicin solution and...