Resistance In Maize Rough Dwarf Virus And Gray Leaf Spot Disease Gene Positioning

Maize is one of the most important crops in China, and both maize rough dwarf virus (MRDV) and gray leaf spot (GLS) are two sever disease limiting yeild production annually. Developing and cultivating resistant hybrids is an effective approach to control the maize diseases, while breeding efforts for resistance rely largely on good understanding of the genetic mechanism. In this study, QTL identification for MRDV and GLS resistance were characterized. The results are follows:(1) The population consisting of 179 F8 families derived from a cross between Ye107 (susceptible parent) and Huangzao4 (resistance) was evolutated for MRDV resistance in replicated field trials in two 'hot spots', Linfen Shanxi province and Baoding Hebei province in China over two years. Genotypic and and G×E variances for disease incidence were highly significant in the population. Composite interval mapping on a linkage map constructed with 74 SSR markers, identified four QTL using three disease index (disease percentage, disease index and modified index), one earch on chromosome 1, 2, 5 and 9,which signification influenced resistance to MRDV. Individual QTL accounted for 4.9% to 43.5% of the phenotypic variance. The resistance alleles of QTL on chromosome 1, 2 and 5 originated from Huangzao4, while the resistance allele of QTL on chromosome 9 derived from Ye107.These QTL have protential use in molecular marker-assisted selection for MRDV resistance in maize.(2) Wide differences were investigated for GLS resistance among maize germplasm sources, and most of the sources of resistance to GLS identified inherited in a quantitative manner, and a number of QTL for GLS resistance have been found using molecular markers. In this paper, the integration QTL map for GLS resistance in maize was constructed by compiling a total of 57 QTL available with Genetic Map IBM2 2005 neighbors as reference. Twenty-six "real QTL" and seven "consensus QTL" were identified by refining these 57 QTL using overview and meta-analysis approaches. Seven "consensus QTL" were found on chromosome 1.06, 2.06, 4.06, 4.08, 5.03 and 8.06, and the map coordinates were 552.53cM, 425.72cM, 279.20cM, 368.97cM, 583.21cM, 308.68cM and 446.14cM, respectively. Using a synteny conservation approach based on comparative mapping between maize genetic map and rice physical map, a total of 69 rice and maize resistance genes collected from websites Gramine and Maize GDB were projected onto maize genetic map IBM2 2005 Neighbors, and 2 (Rgene32, ht1), 4 (Rgene5, rp3, scmv2, wsm2) and 4 (ht2, Rgene6, Rgene8 and Rgene7) positional candidate genes were found in three "consensus QTL" on chromosomes 2.06, 3.04 and 8.06, respectively. Results suggest that the combination of meta-analysis of gray leaf spot in maize and sequence homologous comparison between maize and rice can be an efficient strategy for identifying major QTL and corresponding candidate genes for gray leaf spot.