ABSTRACT
156 Rhizoctonia solani causes sheath blight, which is a widespread disease. ShB reduced severe yield loss by 30–50% in rice-growing regions. No effective management has been developed until now against this ailment. Many cultivation practices are being adopted to block the growth of Rhizoctonia solani. Fertilizers including fungicides could be used in paddy crops but chemicals are being proven to be health hazardous. Apart from this, several breeding approaches like Marker-assisted selection, gene pyramiding, and mutation breeding are commonly used for the development of the resistant cultivar against sheath blight. There are so many QTLs/genes related to SHB that have been identified with the help of proteomics, genomics, and transcriptomics. Sheath blight is governed by quantitative traits so the development of sheath blight resistant rice varieties is much more difficult through the traditional breeding approach. Hence, the pyramiding of QTLs may result in stable and potential rice cultivars. Japonica is one of the resistant cultivar sheath blight which is caused by the pyramiding of the genes qSB-9TQ and qSB-7TQ on chromosomes 9 and 7, respectively. NILs with both TAC1TQ and qSB-9TQ displayed higher resistance than those with just one of them. Improved Pusa Basmati was created by adding the blast resistance gene Pi54 and sheath blight resistant quantitative trait loci (QTL) from Tetep, qSBR11–1. For QTL and association mapping, SNPs are widely used. Rice plants have a huge number of SNP markers and a highly dense rice genome has been built by utilizing 3.6 million SNPs. A study performed the identification of QTLs position, six QTLs were found which were related to sheath blight by using 128 lines of a hybrid between Jasmin 85 (resistant) and Lemont produced an F2 clonal population (susceptible). In another study, 15 more QTLS were derived using a inbreed line population of Tequing and Lemont. Resistant genes like PR-3 chitinase and PR-5 (thaumatin-like protein) like Plant pathogenesis-related (PR) genes provided resistance against sheath blight disease. Instead of a single PR gene, a combination of two PR genes results in a more efficient and greater level of sheath blight resistance. When the Endo-chitinase gene (cht42) was expressed in transgenic rice, sheath blight disease was reduced by up to 62%.
