| SOUTHERN CORN RUST is a destructive disease in maize(Zea may L.). In recent years, it has become a main disease and caused serious yield losses in maize. So it is desirable to exploit the maize germplasm possessing disease resistance against southern rust to improve the disease resistance of present maize hybrids.In this paper, 10 maize inbred lines were used to identify the disease resistance to southern corn rust. Genetic analysis of resistance to southern rust in Qi319 was performed and the resistance gene was mapped by using SSR, AFLP markers. The main results are summarized as follows:1. hi the conditions of both different area and different time, inoculation tests for 10 inbred lines, which commonly used for corn growing and breeding, showed that most of them were susceptible to southern rust. Inbred lines 478, 340, 9801, Luyuan92, Huangzao4 and Huang C were all high susceptible. 1145 and 107 were medium susceptible. While 178 showed medium resistant respondence. Only Qi319 possessed highly resistance to southern corn rust. In addition, an effective method for inoculation on southern corn rust in maize was defined.2. Qi319 (Pi), which is highly resistant to southern rust, and 5 inbred lines 478, 340, 9801, Luyuan92, Huangzao4 (P2), which are all highly susceptible to southern rust, were crossed respectively. The FI generations self-pollinated to produce F2 populations and backcrossed with susceptible parents to produce BCiFi populations. Inoculation was performed on the PI, P2, FI, F2 and BCiFi populations. The results showed that Qi319 and FI were resistance, other 5 parents were susceptible, but F2 and BCiFi populations segregated significantly. Thesegregation-ratios in all p2 generations were 3 I 1 and 1 : 1 in all populations. Therefore, it is confirmed that Qi319 carries a dominant gene for resistance to southern corn rust. We definite this resistant gene for Rpp9-2 temporarily.3. SSR techniques were employed to preUminary mapping of the resistance gene Rpp9-2. Bulked segregant analysis revealed that 2 primer, phil 18 and phi 041, amplified polymorphic bands. SSR analysis on populations indicated the 2 primers were the linkage SSR markers to the rust resistance gene Rpp9-2. And it was mapped to the short arm of chromosome 10.4. Surrounding the region of primer phil 18 and phi041 in maize database, 6 new SSR primers were selected to screening the tightly linkage markers to Rpp9-2. Bulked segregant analysis revealed that all of 6 SSR primers were putatively linked to resistance gene Rpp9-2. SSR analysis on populations of 3 primers, umc2018, umc!293 and umc!318, showed this 3 primers were the SSR markers closely linked to Rpp9-2.5. AFLP techniques were used to identify molecular markers tightly linked to the rust resistance gene. By using 64 primer combinations, a total of 3000 loci were screened on parents and bulks. 2 primer combinations, E-AGC/M-CAA and E-ACC/M-CAT, amplified polymorphic products. AFLP analysis on population demonstrated the polymorphic bands of primer combination E-AGC/M-CAA was the closely AFLP linkage marker to Rpp9-2.6. Genetic map of the region surrounding resistance gene to southern rust Rpp9-2 was constructed. There is 6-linkage marker flanking the resistance gene Rpp9-2 on the map. The closest marker is AFLP marker,3.34cM away from the resistance gene. The closest SSR marker is umc1318, 4.46cM away. And the most distant marker is umc2018, 14.29cM away.7. Comparative analysis of the amplification bands among different populations revealed that the amplification products with the same primer on different populations were dissimilarity. That is to say, the background of gene may affect results of mapping and tagging of genes. So, it is very important to select suitable population to performing gene molecular analysis.
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