MAINTAINERS AND RESTORERS FOR THREE MALE-STERILITY-INDUCING CYTOPLASMS IN RAPE (Brassica napus L.)

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Abstract
The F1 progenies from crosses involving 32 Brassica napus L. strains (including named cultivars) and male-sterile plants carrying one of the three cytoplasms, ogu, nap, and pol were evaluated for male fertility. All strains were found to be maintainers for the ogu cytoplasm. The fertility of the nap male-sterile plants were fully restored by 30 strains. The cultivar Bronowski partially maintained the nap male sterility, and segregation for male fertility/sterility was observed in the F1 hybrid between nap male sterile plants and the cultivar Lergo. Lergo, therefore, appears to be heterogeneous for genes conditioning maintenance and restoration of this type of male sterility. Most strains were maintainers and the balance were partial maintainers for the pol cytoplasm. The F2 and backcross data obtained under a controlled environment suggest that both the cultivars Karat and Westar possess a single dominant gene for the restoration of fertility in nap cytoplasm. Fertility in the pol cytoplasm was restored in the F1 of crosses between pol B. napus and the B. juncea L. Czern. cultivar ZEM. Five male fertile lines of pol B. napus were selected from the ZEM crosses after five generations of backcrossing to B. napus cultivar Regent and three generations of self-pollination. Selection for fertility during backcrossing and self-pollination resulted in selection for an extra chromosome involved with male fertility restoration.Key words: Rape, Brassica napus L., CMS, maintainers, restorers