Mapping Of QTL For Resistance Gene Of Ustilago Maydis And Genetic Analysis Of Yield-related Traits In Maize

Maize (Zea mays L.) is an important food, feed and industrial raw materials cropwith increasing planting areas and total output and then became Chinese first majoritycrop in recent years. Maize common smut is a worldwide disease caused by Ustilagomaydis which always infects corn leaf, stalk, tassel, female inflorescence and otherparts of young tissues and results in the formation of different size tumors. Slowprogress has been made in common smut resistance QTL identification and relatedresearch attributed to the focused research on the pathology, conventional prevention,identification and selection of resistance to disease.In this study, a set of scientific and efficient inoculation methods wasestablished.And a population including F2:3family lines was developed from thecrossing of Ye478IL87(highly resistant)×Ye478(highly susceptible) to positionR-QTLs of common smut.In addition, there was a two locations phenotypicallyevaluated field test with the237F2:3families population crossed fromZong3×HB522,in which the genetic characteristics of six yield-related traits wasevaluatd.The main results were as follows:1. Established a set of cultivation of Ustilago maydis and identification methodof resistance to Ustilago maydis. Basidiospore strains of Ustilago maydis was culturedfor20-22h, happens to be the point-in-time of themiddle of “S” logarithmic growthcurve.the score of basidiospore OD560was2.3, corresponding the6×105/mL sporeconcentration. The growth status and operability of the fungus were ideal during thisculture period.2. Screening of198Polymorphism SSR Markers in Ye478and Qi319, and34Polymorphism SSR Markers in Ye478and Y478IL87. The background recovery ratioof Y478IL87was91.4%, introgressed segments on chromosome2ndand7thwas0,while on chromosome1st,3rdand10thwas single segment, there were moreintrogressed segments on the other chromosomes. The genetic linkage map including28SSR markers, which covered531.7cM, with the average genetic distance of18.9cM.3. Under the natural field condition of artificial inoculation, R-QTL loci wasfound in10.04bin in2011, whose score of LOD was4.5795and phenotypic variation explain contributed up to11.9307%. In2012, five QTL were detected in fivephenotypic by using composite-interval-mapping method, which located in4.08bin,6.05bin,8.06bin and9.02bin, which can explain1.973%-28.683%respectively. TheLOD score of the4.08bin QTL scanned was12.398, with a phenotypic variationexplained21.234%. Higher phenotypic variationwas and LOD score detected on theQTL. The confidence level in95%was determined by using permutation test, toeliminate the QTL of below threshold.4. Three unlinked QTLs were located on chromosome5and6respectively bysingle-marker-mapping method which can explain10.660%-21.117%.phenotypicvariation. The LOD score of the6.05bin QTL scanned was6.021, with a phenotypicvariation explained13.007%. This QTL maybe the same one on6.05bin detectedby using composite-interval-mapping method.5. The test with the237F2:3families population crossed from Zong3×HB522.Among six maize yield-related traits,the kernel row number and the ear diameter hadhigher broad-sense heritability (Hb2%), followed by kernels per row, kernel weightper ear, ear weight and ear length. The descending order of the F1generationmid-parent and over-parent heterosis in six traits was the kernel weight per ear, earweight, kernels per row, ear length, row number and ear diameter. Obvious depressionof inbreeding were observed in F2:3families. The coefficient of variation (CV) ofkernel weight per ear was the highest, followed by the other five traits: ear weight,kernels per row, ear length, row number and kernel weight per ear. The kernel weightper ear was significantly correlated with the ear length, ear diameter, row number,kernels per row. Kernels per row were more effective in promoting kernel weight perear.