Breeding maintainer and restorer lines of cytoplasmic male sterility resistant to Phytophthora capsici in capsicum pepper

摘要

In order to breed Phytophthora blight (Phytopthora capsici Leonian)-resistant maintainers and restorers of cytoplasmic male sterility, a maintainer (CMS-B, Nrfrf) line of pepper (Capsicum annuum) was crossed with Phytophthora blight-resistant lines,'AC2258' and 'SCM334', genotype of which had been identified as restorer (CMS-C, NRfRf). An evaluation and selection for resistance to P. capsici were conducted on the F_5 and F_6 lines of the crosses developed by pedigree method. Plants selected from the F_5 lines were crossed with a cytoplasmically male sterile line, 'Chilsung CMS-A' (Srfrf), to identify the nuclear genotype interacting with the male sterile cytoplasm. Seventy nine of the 95 crosses between CMS-A and F_5 plants for the cross CMS-B XSCM334 produced male fertile plants. As such, the selected F_5 plants were identified as restorers (NRfRf), while the remaining 15 were segregated, indicating that the genotype of the F_5 plants was heterozygous (NRfrf). Since only one cross resulted inmale sterile plants, this suggests that the F_5 plant was a maintainer (Nrfrf). Similarly, 24 of 31 selected F_5 plants derived from the cross CMS-BAC2258 were identified as restorer, while the remainder were heterozygous. Therefore, maintainers were unexpectedly rare. Since maintainers were expected to occur in a similar frequency as restorers once the genes conferring resistance to P capsici and the restore gene segregated independent of each other, this suggests a possibility of linkage between the restore gene and the genes conferring resistance to P. capsici. The plants selected for resistance to P capsici from the F_6 lines derived from heterozygous or maintainer genotype F_5 plants of the two crosses were then crossed with the CMS-A line again to identify their genotype. Twenty three of the 101 plants selected from the F_6 lines of cross CMS- B X SCM334 were identified as restorers, 21 as maintainers and the remaining 57 as heterozygous or uncertain. Meanwhile, 4 of the 23 plants selected for resistance from the F_6 lines of the cross CMS-B X AC2258 were identified as restorers, 10 as maintainers and the remaining 10 as heterozygous or uncertain. Accordingly, the maintainer and restorer lines can be used in breeding F_1 hybrids with a high level of resistance to P. capsici.