| Sheath blight(SB)is one of the most serious global rice diseases that seriously affects the yield and quality of rice.At present,the research on rice sheath blight is mostly focused on the preliminary positioning of disease-resistant QTL.There are few genes for fine mapping and cloning,and the progress of disease resistance breeding is slow.In this study,chromosome segment substitute line populations(CSSLs),which were constructed by Changhui 121(resistant variety)and Koshihikari(sensitive variety),were used as research materials.The linkage analysis and transcriptome sequencing were used to analyze the genes related to rice sheath blight resistance,which provided a theoretical basis for the genetic improvement and breeding of rice sheath blight resistance.The main experimental results are as follows:1.Further construction of the chromosome segment substitute line population with the parent of Koshihikari and Changhui 121 as the donor parent.Using 127 SSR markers,306 families were selected by molecular marker-assisted selection,the target substitution fragments were tracked,and the genetic background was further purified to obtain 108 candidate individuals.The average number of molecular markers per single plant substitution was 10.71,accounting for 8.44% of the total number of markers,of which10.13 were homozygous donor genotype markers and 0.58 were heterozygous genotype markers.All substitution fragments covered 12 chromosomes and covered the whole genome at 1427.7 c M.2.The QTL mapping was performed using the chromosome segment substitute line population with the parent of Koshihikari and Changhui 121 as the donor parent,and the relative disease level(DR)was used as the disease index.Using QTL Ici Mapping4.1software,6 QTLs were mapped and detected on chromosomes 2,3,4 and9,respectively,explaining the phenotypic variance from 6.24% to 18.51% and additive effect of-1.25～1.6.Using overlapping substitution mapping method,9 QTLs were located and detected on chromosomes 2,3,5,6,7,and 11,with explaining the phenotypic variance of 7.57% to 13.23% and additive effect of-1.01 to 0.6.3.The QTL mapping was performed using the chromosome segment substitute line population with the parent of Changhui 121 and Koshihikari as the donor parent,and the relative disease level(DR)was used as the disease index.Using QTL Ici Mapping4.1software,8 QTLs were located and detected on chromosomes 1,2,3,5,7,11,and 12,with explaining the phenotypic variance of 5.85 to 21.92%,and additive effect of-2.83 to 0.45;For overlapping substitution mapping method,5 QTLs were located and detected on chromosomes 2,6,7,8,and 12,with explaining the phenotypic variance of 22.6-26.67%and additive effect of 1.15-15.36.4.Qsb-2-1,qsb-2-2,qsb-2-3 and qsb-2-5 which were located on marker interval B2-10～RM3762 of chromosome 2,qsb-3-1 was located on marker interval RM15887～RM15903 of chromosome 3,qsb-5-1 and qsb-5-2 were located on marker interval RM3476～RM3790 of chromosome 5,and qsb-6-1 was located on marker interval RM1369～RM1163 on chromosome 6.These QTLs were detected in both groups,indicating that resistance genes may be present at the QTL site.5.According to the results of QTL mapping,phenotypic results of resistance identification and substitution fragment intervals,select chromosome segment substitute lines Y60,Y85,Y103 and Koshihikari parents as materials,Illumina sequencing analysis before inoculation and inoculation after 18 h of Rhizoctonia solani,a total of 1376,003,644high-quality clean reads were obtained,and the ratio of the ratio to the Japanese Nipponbare genome ranged from 72.2% to 96.62%.The three lines and Koshihikari obtained 5118,2579,3904 and 2022 differentially expressed genes(DEGs),respectively.Combined with the results of QTL mapping,multiple differentially expressed genes were enriched in resistance-related pathways,such as diterpenoid biosynthesis,phytohormone,MARK signaling,indicating that these genes are involved in the regulation of immune responses against defense pathogen infection.May be related to resistance. |
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