QTL Analyses For Head Smut And Major Correlated Traits In Maize

Head Smut is one of the most important diseases of maize in the world. Ithappens in the most maize zone at different levels. It has already become one ofthe most serious diseases, causing a significant yield and quality losses, especiallyin maize spring area of China. The advent of molecular markers and QTL mappingmethods in the last decade provides an opportunity to deeply study the geneticprinciples of resistance to head smut. In this study, a F2 population with 191individuals, derived from a cross of Huangzao4×Mo17, is used to construct agenetic map and locate QTLs of head smut and correlative agronmic charactersand analyse the genetic effect. The main results are summarized as follows: (1) From 330 SSR primer pairs, 87 amplify polymorphism clearly betweentwo parents. These 87 polymorphic loci were used in analysing genotypes of the F2population. In the F2 population, the allele frequencies of Huangzao4 and Mo17 inall 191 informative loci are 48.13 % and 52.97%, respectively.The allele ratioapproximated to the expected 1:1. Chi-square test indicated that 21 markers(24%of all) skew from the expected 1:1 gene segregation, and 17 markers (20% of all)skew from the expected 1:2:1 genotypic segregation. These skew loci most lie in 2and 6 chromosomes. (2) The genetic linkage maps were constructed with 87 SSR markers based ona maize population consisting of 191 F2 individuals from the cross Mo17×Huangzao4, covering 1655.4cM on total ten chromosomes with an averageinterval length of 19.03cM. With the method of composite interval mapping, fiveQTL conferring resistance to head smut were identified on chromosomes1, 2, 3, 4and 7 in F3 populations in Harbin; six QTLs conferring resistance to head smutwere identified on chromosomes1, 2, 3, 6, 8 and 9 in F3 populations in Jilin,respectively. Combined analysis identifys four QTLs, which are identified in Harbinand Jilin on chromosomes 1, 2 and 3. The other QTL is identified on chromosome 4,contributing a low phenotypic variance. (3) The linear correlation between disease incidence of head smut and grainyield, plant height, 100-keneral weight, were all highly(p≤0.01) or sinificant(p≤0.05). (4) With the method of composite interval mapping, four QTLs conferringgrain yield under inoculating were identified on chromosomes1, 2 and 3 in F3populations; four QTLs conferring plant height under inoculating were identifiedon chromosomes4, 8, 9 and10; two QTL conferring 100-keneral weight underinoculating were identified on chromosomes 6 and 9 in F3 populations,respectively.