| The Maize Gray leaf spot(GLS) is a world main disease caused by Gercospora Zeae-maydis, it mainly occurs in the maize leaves, leaf sheath and bracts. The maize resistance of GLS disease belongs to quantitative traits. This study aims to find a chain of molecular markers closely with resistance genes by maize GLS resistant disease QTL analysis, and carry out the Marker-assisted selection, improve the efficiency of breeding, provide basis for breeding more elite lines or varieties. This research adopts the corn high resistant inbred lines T32 and high susceptible inbred lines J51 equipping the F2 generation for constructing SSR marker genetic linkage map, F2:3 family are planted in the town of Mengga and Jiangdong two high incidence area of gray spot disease in Mang city of Dehong prefecture of Yunnan province. The main research results as following :1. With high resistant of GLS inbred lines T32 as female parent, high susceptible inbred lines J51 as the male parent, built 189 F2 strain for drawing. According to Maize GDB information, selected the 880 to cover corn genome-wide SSR primers of two parent screens, polymorphism screened 137 pairs of polymorphic primers, the polymorphism proportion is 15.6%. This study on screening out the polymorphism of DNA primers increase F1 combination of IBM reference map for further screening,out of them as the dominant, the instability of amplification and difference is small,it is difficult to distinguish markers, choose can amplify a stable and clear bands in group a total of 89 markers eventually into the construction of linkage map.2. Using the drawing software Join map version 3.0, analyze linkage for 89 pairs of polymorphic primers, build the F2 population genetic linkage map containing 12 linkage group, including 4 and 8 chromosome chain is divided into two groups, build the linkage map 86 SSR loci were fitting, general genetic distance of 828.369 c M,the average distance between markers of 9.62 c M. Most markers and standard atlas IBM2 2008 Neighbors Frame6(http://www.maizegdb.org) position is consistent,conform to the preliminary analysis QTL.3.189 F2:3grown in the village Mengga town Mengga Dehong prefecture of Yunnanprovince and Jiangdong town Li Ziping village two environments, each sites grow repeat twice, in the field of natural disease. According to the national standards of spot investigation, survey field natural infection situation of F2:3in milk stage. The phenotypic characterization results show:in Jiangdong and mengga, disease-resistant parent T32 was consistent high(grade 1), infected J51 parent was consistent high susceptible(9), F1 was consistent resistance level(average disease Mengga is 3.3 and Jiangdong is 2.3), F2:3are obvious sense of separation.Using SPSS20.0 carry on the normal distribution test for F2:3189 groups average disease level, from the perspective of skewness and kurtosis two parameters(the absolute value is less than1), there was no significant deviation from normal distribution, satisfies the basic demands of QTL mapping. Character distribution of continuous distribution, the number of display can be controlled by poly-gene disease resistance trait;Distribution has obvious peak, suggesting that there may be the main effect QTL controlling the traits.4. The complete interval mapping method is adopted for the two sites of F2:3illness level survey result resistant resistant QTL detection and genetic effect analysis, in Jiangdong three resistance QTLs detected, located on the chromosome 4 and 8.Respectively, of which two QTLs were detected on the chromosome 4, additive effect are-0.3656,-0.7086 and-0.2171 respectively, both from the parent T32,explains respectively 7.0047%, 22.0517%, 7.368% of the phenotypic variation. Six QTLs were detected respectively in chromosomes 1, 2, 4, 7 and 8 in Mengga,including position in chromosome 1 QTL for 139.00 and chromosome 2 QTL additive effect on the chromosome from parent J51, effect value of 0.3123 and 0.3500.Respectively, contribution rate are 5.0219% and 5.0219% respectively. The rest of the additive effect of four QTLs were from parent T32, effect value is :0.2422,0.2790, 0.3779 and 0.5657. Respectively account for 4.2467%, 3.9767%, 6.8053%,12.9815% of the phenotypic variation.5. The result of Jiangdong and Mengga two sites combined in the field of the QTL analysis shows, detecting 1 QTL in the two environments at the same time, located on chromosome 8 between umc1130 and umc2354, position on the graph is:10.00.In two-point LOD values are : 3.3135 and 5.9711, explaining the resistance of corn resistant 7.3680% and 12.9815% respectively of phenotypic variation, additive effect were from the maternal T32. The QTL can be used as a corn resistant disease marker-assisted selection candidate chromosome segments, for the genetic mechanisms of corn resistant disease research to provide theoretical reference.According to the result of QTL genetic effect analysis, shows that genes way is given priority to with partial dominant effect and additive effect, but also has dominant effect and the role of dominant effect way. |
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