QTL Mapping Of Resistance To Maize (Zea Mays L.) Dwarf Mosaic Virus

Maize dwarf mosaic, caused by maize dwarf mosaic potyvirus (MDMV), is an important widespread virus disease of maize in the world. It has also become a major concern in China, causing a significant yield loss in production. The advent of molecular markers and QTL mapping methods in the last decade gives an approach to study the resistant mechanism of maize to MDMV. In this study, a F2 population with 184 individuals, derived from a cross of Huangzao 4 X Ye107, is used to construct a genetic map and locate QTLs of MDMV-B. The results are summarized as follows: 1. Among 222 SSR primer pairs, 54 amplify polymorphism clearly between two parents, of which one pair (bnlg292) is identified 3 polymorphic loci. These 56 polymorphic loci will be used in analyzing genotypes of the F2 population. 2. In the F2 population, the allele frequencies of Huangzao 4 and Ye 107 in 56 informative loci are 51.2% and 48.8% respectively. The allele ratio approximates to the expected 1:1 .Chi-square test indicates that four markers (7% of all) skew from the expected 1:1 gene segregation. Ten markers (18% of all) skew from the expected 1:2:1 genotypic segregation. 3. A genetic linkage map is constructed by Joinmap program, covering 8 maize chromosomes except chromosome 2 and 4. Forty-two loci are located on the map. 4. Methods used to detect QTL include one marker analysis using simple linear regression (SLR), interval mapping (IM) and composite interval mapping (CIM): SLR detects significant loci on chromosome 3 6 and 10; IM and CIM both detect 4 QTL on chromosome 3 (2 QTL) 6 (1 QTL) and 10 (1 QTL). The nearest markers to each QTL are 1035 phiOS3 phiO77 and phiO62 respectively. Gene action is additive or partial dominance. The 2 QTLs on chromosome 3 explain more than 40% of the phenotypic variance. There is a high agreement among the results of the three methods. 5. BSA (Bulk Segregation Analysis) is performed in the 54 polymorphic SSR primers. Four primers (1035 phiOS3 phiO29 phiO99) show polymorphism between the resistant and susceptible bulks. Linkage analysis of the 4 primers in F2 population (25 resistant and 25 susceptible individuals) indicates that the nearer primers to MDMV-B resistance gene are 1035 and phiO53 with map distance 21.5cM and 25.1cM, respectively. 6. The QTLs are maPped on chromosomal bin 3.04, 6.0l. l0.04, of Which3.04 and 6.01 are considered to be clustering region of disease and insectresistance genes in maize. The result confirms the existence of clusters of diseaseand ipsect resistance genes.