Screening Resistant Resources Of Rice Sheath Blight And Mapping Resistance QTL

Sheath blight (ShB) is one of the three major rice diseases. The ShB-resistant varieties is the mosteconomical and effective way to control ShB. Screeningnew resistantce resources and durable resistancegenes/QTL is the base and prerequisite for breeding resistant varieties.A total of152rice landraces fromdifferent regions have been tested under field conditions in three environments to mine the stableShB-resistant germplasm resources, meanwhile, two F2and a F2:3mapping populations from the crossbetween Lemont (japonica, a susceptible cultivar from America) and Yangdao4(indica, a cultivar withresistance to ShB from China),were used to map QTLs for ShB resistance in three environments.Themain results are as follows:1.The152rice landraces were innoculated and tested for ShB resistances under field conditions inthree environments (two in Hangzhou, one in Hainan). They exhibited various resistance to sheat blight,which meant resistant difference not only existed in the same rice strains, but also changed with years.Among the tested materials, we detected high-resistant cultivars, nevertheless, with instability. It couldbe concluded that different subspecies of rice are less correlated with their resistance to ShB diseasewhile Japonica rice could be also high resistant.2. In order to utilize materials with high resistance in breeding, we focused on their resistantncereaction especially under conditions of Hangzhou. In total we found no stable highly resistantmaterials while12susceptible varieties(Maybelle, Wenguang, Gongxiang, Vista, Kongyu131,Jinxiandao, Bashizao, Weiguo, Aijiaonante, black awn rice, Laolaiqing, patriotic)were identified,which could be utilized as sensitive material controls both in appraising of resistance to ShBexperiments and the underlying genetic analysis of resistance. Of the24varieties (Laobaishu, GuinongZhan, Guangchao1, Guangfeng Zhan, Taihang68, RAJBHOG, Shuangzhu Zhan, Zihong, Nongken58,Shunhezao, Yuehui Zaozhan, Yuxiangyou Zhan, Huangfeng Zhan, Yinhesi Zhan, Yangdao4,93-11,Huangli Zhan, Dianlong201, Zhongjian2, Shuangzhen Zhan, Digu, Rohini, Wuzuinuo, Zhejaponica27)showing resistant to ShB disease in successive two years of Hangzhou, especially Guangchao1andZihong, were resistance to sheath blight in three environments, which can be considered as favorabledonor materials for resistance breeding and genetic analysis.3. A genetic linkage map was constructed based on Lemont/Yangdao4F2population by usingMapMaker/EXP3.0software, which consists of180markers and covereda total of1996.2cM with anaverage interval of11.8cM between adjacent markers. QTL analysis was performed in threeenvironments (E1~E3), and three traits were recorded to evaluate the ShB resistance, namely diseaserating (DR), lesion height (LH), and percentage of lesion height (PLH). A total of21main QTLs forresistance to sheath blight (Among them, eight QTLs for DR,Six QTLs for LH, Seven QTLs forPLH)were detected, and located on6chromosomes(Chr1,3,4,7,11,12). This study found that qSBL-7andqSBPL-7are two new QTLs for ShB resistance, which have not been reported.4.By comparing the locations of the ShB-QTLs detected in multiple environments, we found six clusters with16co-located ShB-QTLs, which located at interval of D328B~D331B, D333B~D334,D760~RM248, D1103~RM26155, RM26155~D1113and RM1246~D1260, respectively.5.In order to explore the relationship between ShB-QTLsand plant height-QTLs, QTLs analysis forplant height were also performed in the three environments.A total of five QTLs for plant height,namely: qPH-1, qPH-2, qPH-3, qPH-4andqPH-6,were detected in the present study. There was onlyone QTL for plant heightlocated on the same region with ShB-QTL, and other four QTLs for plantheight distributed in different chromosomal regions.