Linkage disequilibrium and association mapping of sheath blight resistance in rice (Oryza sativa L.)

The productivity of rice is affected by infection of Rhizoctonia solani, which prompts to search for resistance sources from the available germplasm. An effort has been made to understand the heritability and QTLs of the traits related to sheath blight (SB) resistance in rice. A core panel of 192 genotypes was formed from 330 rice accessions based on the disease reaction against SB for association mapping studies. The study confirmed that population had significant amount of genetic variation for SB related traits across seasons. The correlation analysis showed positive association between PDI’s and AUPDC and negative association between PDI and plant height, flag leaf length, and grain yield. 133 microsatellite markers classified the genotypes into three major clusters, while model-based approach grouped the genotypes into two subpopulations. By employing both GLM and MLM (Q+K) models, 30 SSRs were associated with targeted traits across seasons. Eight QTLs namely qPh.2-1, qShB.4-1, qShB.4-2, qPh.8-1, qShB.8-2, qShB.10-1, qShB.10-2, and qPh.12-1 were novel QTLs related to sheath blight resistance and plant height traits. Further, elite alleles associated with markers imparting resistance against sheath blight was identified in IC283139, IC 277248, Sivappu Chithirai Kar and Bowalia, which would be useful in developing rice varieties with durable disease resistance.