Meta-analysis Of QTL For Rice Sheath Blight Resistance And Development Of Chromosome Segment Substitution Lines Using Resistant Cultivar YSBR1 As Donor And Gene Mapping

Rice is one of the most important food crops in the world.As one of the three-major rice diseases,rice sheath blight caused by Rhizoctonia solani is the first among all the rice diseases.Cultivation and promotion of resistant varieties is the most economic and effective way to control disease.However,it is hard to breed disease-resistant varieties by means of conventional breeding,because rice sheath blight resistance is typical quantitative trait and vulnerable to environmental impact.Molecular marker-assisted selection of QTL for resistance to sheath blight is regarded as a feasible way of cultivating disease-resistant varieties.At presents the location of QTL resistant to sheath blight is generally not highly reproducible and its effect is small.Therefore,it is of great theoretical and practical significance to explore QTLs resistant to sheath blight with high reproducibility and significant effect.In this study,we collected published data of on QTLs of against to rice sheath blight,as well as those QTL information of plant height and heading date that could easily affect resistance to sheath blight were also collected.Then,the consistency analysis(Meta-analysis)was carried outr so as to explore the consistency QTLs of resistance to sheath blight with high reproducibility and no other traits interfere.Meanwhile,we use YSBR1,a germplasm with high resistance to sheath blight,as the donor parent to construct whole-genome chromosome segments substitution lines(CSSLs)under the background of Taigeng394(T394),a super rice variety promoted in Jiangsu province.From this,the QTL of resistance to sheath blight and important agronomic traits were identified.The main results are as follows:1.We collected 23 literatures published about rice sheath blight resistance genetic mapping,organizing 207 QTLs of the sheath blight resistance(qSB),109 QTLs of heading date(qHD),62 QTLs of plant height(qPH),Meta-analysis generated 49 consensus QTLs of sheath blight resistance(MqSB),28 consensus QTLs of heading date(MqHD),16 consensus QTLs of plant height(MqPH),37 MqSB were found without the distraction of consensus QTL related to MqPH and MqHD,which have essential research value.At the same time,we analysed 6 sets of transcriptome data and found that the differentially expressed genes in the MqSB interval were more related to the accumulation of defense substance in rice and the signal pathway of susceptibility response induced by pathogenic bacteria.Further combined with the published gene tissue specific expression data,the candidate genes of 10 MqSB with confidence interval less than 100Kb were analyzed,and 28 candidate genes were selected,which provided the information foundation for the verification of candidate genes2.A total of 280 polymorphic molecular markers were used to assist with selecting YSBR1/T394 CSSLs from 224 BCnF3 generation lines and obtained 123 CSSLs with different segments,which accumulatively covered 80.5%of YSBR1 genomic information.Combining agronomic traits and sheath blight resistance identification data of these CSSLs,using the QTL Lcimapping v4.0 software for QTL analysis.There were 5,4,10,4,2 and 6 QTLs associated with plant height,heading date,fertility,glabrous leaf,spike type and resistance to sheath blight.There were 5 cloned related trait genes in the QTLs,and 3 QTLs(qSB2,qSB4 and qSBll)that overlapped with the 3 MqSB intervals obtained by Meta-QTL analysis in this study.3.At the early stage,our group identified two primary resistance QTLs(qsb-2YSBR1 and qsb-12YSBR1).We used 40 YSBR1/Lemont CSSLs covering the confidence intervals of the two QTLS to conduct field and greenhouse resistance identification,and further located qSB2 between ZY31.2-RM166 on chromosome 2,with a 3.2Mb region.It is believed that there are two tightly linked resistance genes in the qSB12YSBR1 interval,one is ZY25.2-RM235 and the other is RM6217-ZY25.1,with physical spacing of 0.9Mb and 2.5Mb,respectively.In addition,46 CSSLs related to the interval of QTL qSB-9TQ were repeatedly located,which further confirmed that qSB-9TQ was located in the interval of Y84-Y86,which completely contained MqSB-9-5 and the previously reported fine mapping interval.The above results provide great material basis for further cloning of rice sheath blight resistance and important agronomic trait genes/QTL,which has important theoretical value and practical significance.