Sharma, ManmohanKiran, Usha2021-02-162021-02-162020-12Preferred for your work. Kiran, U., 2020.36599https://krishikosh.egranth.ac.in/handle/1/5810161253Rice blast disease caused by the fungus Magnaporthe oryzae, poses a serious threat to the rice production world over. Deployment of host-plant resistance, has proved to be the most economical and environment friendly option for managing the disease. The present investigation entitled “Molecular marker assisted pyramiding of Pi9 and Pi54 blast resistance genes in rice cultivar K 343” was carried out at School of Biotechnology, SKUAST-Jammu from 2015-2019 to pyramid blast resistance genes in the genetic background of rice variety K 343; to validate the introgressed genes in the target background using SSR markers; and to evaluate the pyramided lines for different traits to identify superior genotypes. K 343 was used as recipient parent which is an elite Indica rice cultivar while DHMAs and RML 22 were used as donor parents for Pi54 and Pi9 genes, respectively. For Pi54 gene, closely linked SSR marker RM 206 (0.7 cM from locus) and for Pi9 gene SSR marker AP5930 (0.05 cM from locus) were selected for foreground selection. A total of 101 genome wide polymorphic SSR markers were selected and used for background selection to find out the percent recovery of recurrent parent genome using GGT 2.0 software. Foreground and background selection in BC2F1 stocks led to identification of three plants (P1, P3, P17) in K 343*3/DHMAS population and three plants (P3, P11, P28) in K 343*3/RML 22 population which were positive for target gene and had recurrent parent genome recovery more than 85 percent with broader similarity with recurrent parent with respect to agro-morphological traits. Screening of both BC2F1 populations with PLP-1 strain of M. oryzae depicted that these plants showed resistant to highly resistant reaction. Simultaneous foreground selection of Pi54 and Pi9 genes in F2 convergent population (comprising of 4000 plants) depicted 45 plants positive for both Pi54 and Pi9 genes. Background selection of gene positive plants led to the identification of 8 pyramided plants (P4, P5, P6, P8, P16, P37, P42 and P45) which had recurrent parent genome recovery more than 90 percent and agronomical similarity with recurrent parent genome and highly resistant reaction to blast fungus. It indicated the strong resistance nature of Pi54 and Pi9 genes together to the predominant fungal strain (PLP-1) of Magnaporthe oryzae. The identified lines showed low amylose and moderate protein content. These pyramided plants can be further used as genetic stocks for identification of blast resistance varieties or can be used as donors of genes Pi9 and Pi54 in breeding programmes.EnglishThesis