Inheritance And Quantitative Trait Loci Mapping Of Resistance To Head Smut Caused By Sphacelotheca Reiliana(K(?)hn) In Maize

Head smut is a kind of prevailing worldwide disease infected by Sphacelothecareiliana. Since 1990s, it becomes one of serious diseases in areas yielding maize inChina with the diffusing of the disease, and is aggravated year by year. It is obviousthat selecting and breeding new resistant varieties is the effective way to control thedisease. However, the achievements of breeding resistant cultivars depend on thedegree of understanding on the genetic basis of resistant germplasms and its characters.It has an important significance on resistant breeding to head smut to study theirantigen and genetic rules. The major research results in the dissertation are as follows.After inoculating and identifying 133 inbred lines and 24 populations in twoyears (2003-2004), 44 resistance lines were screened and identified , including 26resistance lines (Mo17, Zhong 31 and Zheng58 and et al), 8 high resistance lines(Qi319,Jie853,Moqun17,and et al), 4 resistance colonies and 6 medimu resistancecolonies. The germ plasm of Tangsipingtou was the worst one in resistance to headsmut. The germ plasms of PA, lvdahonggu, BSSS, PB and Lancaster had the highertesistance in turn. Their average percent of resistant individual plant were 61.2%,23.72%,19.23%,17.66%,15.1% and 13.86%, respectively.The genetic analysis of inoculation experiment for 6 generations of 4 hybridcrosses, resistance ×sensitivity, showed that each cross had significant additive effect.And one of them had significant dominance effect with different effective direction.The different hybrid crosses have different genetic model on resistance, and wereinfluenced by genetic background of sensitivity parents. Two crosses, Qi319×E28 andMo17×E28, accorded with the model of additive-dominance. On the contrary, crosses,Qi319×Huangzao4 and Mo17×Huangzao4, performed epitaphic effect. The genotypic data of 191 F2 individual derived from cross, Mo17×Huangzao4,were analyzed using SSR and AFLP markeres. Linkage map including 82 SSR and136 AFLP markers were constructed using Mapmaker3.0.,Which covered 1956.1cMon chromosome, with average distance of 9.34cM between markers. 184 F2:3 population derived from 191 F2 individuals of cross, Mo17×Huangzao4,were identified by the means of inoculating in Gongzhuling in 2003 and 2004. .6 QTLof head smut were detected using composite interval mapping , which were located onchromosome 1,2,2,3,3 and 8, respectively in 2003. Phenotypic variation explainenby single QTL ranged from 6.63 % to 43.72%. Their genic action model of QTLperformed additive and partial dominance. 8 QTL contributing on chromosome1,2,2,3,3 and 8, respectively. were detected in 2004. Phenotypic variation of single QTLranged from 4.58% to14.07% , and their genic action model showed partial dominance,dominance and super dominance. Comparing the mapping results mentioned above,QTL were detected in 1.03-1.04, 2.09, 3.04-3.05, 8.02 on chromosome in two years.Especially, the QTLs in 2.09 and 3.04 bin were located nearly on the same site,explaining larger phenotypeic variation and having the same t gene effect direction. Results of resistant analysis on 184 F3 population from cross, Mo17×Huangzao4,in two years were used to construct resistance and sensitivity DNA pool ofcorresponding F2. The polymorphic SSR and AFLP primers in 2.09 and 3.05 bin werescreened. The segregating population was analyzed using the selected primer. Finally,there were 8 SSR and 5 AFLP markers significant relative to head smut. The partialgenetic linkage map was constructed and the resistant QTL was also detected usingcomposite interval mapping. At last, resistant QTL were found in 2.09 and 3.04 bin,with additive and partial dominance effects, respectively. Phenotype variationexplained by single QTL is 14.95%~28.84% and 11.42%~12.47%, and the markersnearest to QTL were P4453336 and P4244143.