Linkage Mapping Of Rf4 A Fertility Restorer Gene For C-cytoplasmic Male Sterility In Maize

One of the most significant achievements in agriculture during the twenty century is the use of heterosis on crop plant breeding. Maize heterosis is a typical example. Using of cytoplasmic male sterility is an important way to achieve heterosis. Maize is the first crop applied male sterility for hybrid seed production, it play an active role in reduction of production costs and improving seed purity. C-type cytoplasmic male sterility is the mainly applied type in maize heterosis seed production, however, the molecular mechanism of the restoration of C-type cytoplasmic male sterile is far from clear, which has hampered the extending of its use.Using the restoration line Fengke 1 and A619 and the male sterile line CMS-C237, CMS-CMo17 hybrid combination, the genetic analysis showed that Fengke 1 contains 2 pairs of overlapping gene, restorer gene Rf4 and Rf5; yet A619 contains only restorer gene Rf4. Using SSR markers we had positioned C-type cytoplasmic male sterile maize restorer gene Rf4 and Rf5 on 8 and 5 chromosome, respectively, and discovered a dominant suppressor gene Rf-I of Rf5. C-type cytoplasmic male sterility restorer gene Rf4 was flanked by SSR marker bnlg2037 with the genetic distance for 25.4cM. Also by using the RFLP marker, we found that the restorer gene Rf4 linked to probe npi220 and csu29, the distance from the two probes were 7.1cM and 18.8cM, respectively.This research in the prophase research, using the SSR markers and AFLP had positioned the restorer gene Rf4. Fine mapping of the restorer gene Rf4 by using the information of corn group to the development the SSR and intron molecular markers. The results were obtained as following:In this study, a set of NILs were used to construct the 1800 BC1F1 mapping group, which contains the restorer gene Rf4. To further position Rf4, 20 pairs of SSR primers of maize on 8 chromosome (8.00 and 8.01) were screened, and found that the marker IDP3939 was linked to Rf4, but is on the right side of the probe npi220. Using 4096 pairs AFLP primer combinations to select two parents, found no AFLP marker was linked to Rf4. Benefitting from the maize genome sequencing project, we used microsatellite SSRHUNTER search tool on the 8.00 district 15 BAC's BAC-SSR markers for the development, designing primers in polymorphism between the parents. 60 pairs of SSR primers were developed. Among them, 12 pairs of primers exhibited polymorphisms between two parents. Using developed molecular markers to test exchange seedlings, Rf4 was positioned in the 8.00 district, between 42-6 and 18-6, the physical distance was about 0.4MB in base of the physical map of B73.this study achieved the exchange between genetic map and physical map, and made a foundation for map-based cloning of maize restoration gene Rf4.