QTL Mapping for Resistance to Fusarium Ear Rot in Maize

【Objective】In order to discover some basic regulations of maize’s resistance to Fusarium ear rot in Guangxi, where maize was planted by the cropping system of two crops a year and had beneficial occurrence conditions to Fusarium ear rot, the objectives of this study were to detect QTLs (quantitative trait loci) associated with resistance to F. verticillioides and to provide some theoretical basis for the resistance breeding of maize ear rot in these areas.【Method】 Based on the genotypic date of 148 polymorphic SSR markers among 215 F2 plants, a linkage map was constructed by using software Mapmaker 3.0. F2:3 lines, which developed from 215 F2 plants, were artificially inoculated to identify their resistance to Fusarium ear rot by using the needle-punch method in Nanning.The infected grade of every plant in a line was recorded after field investigation, then all the infected grades in a line were transformed into resistance index of corresponding line. The resistance QTLs were analyzed by composite interval mapping (CIM) method of software WinQTLCart 2.5.【Result】 A linkage map was constructed 148 SSR markers, covering 10 maize chromosomes with a total length of 1 396.3 cM and the average genetic distance of 9.43 cM. The obtained LOD threshold value was 2.2 after the permutation test calculation was conducted for 500 times with the disease resistance index at a significant level of 0.05. Based on this threshold value, 3 disease resistance QTLs were detected. The result of gene action showed that these 3 QTLs were over-dominant, over-dominant and partial dominant, respectively. These QTLs had both positive and negative effects on additive value, which reflected that there were minor resistance genes in both resistant and susceptible parents.【Conclusion】The 3 QTLs were located on chromosome 2, 3 and 10, explaining 4.6%-6.6% of the phenotypic variation and they were minor resistance QTLs. No major resistance QTL with large effect value was found in this study.