Establishing an association between molecular markers and sheath blight ('Rhizoctonia solani Kuhn') resistance in rice

Abstract

The use of multiple regression analysis to validate molecular markers associated with sheath blight resistance was carried out in 73 germplasm accessions of rice. Data on disease reaction was recorded as lesion size and used for calculation of AUDPC (Area Under Disease Progress Curve) and Percent Disease Index (PDI). A variation in AUDPC ranging from 217.78 to 793.33 with a mean value of 532.51 was recorded for the genotypes infected with sclerotia. PDI ranged from 28.89 to 84.44 with the mean values of 55.40 for infected lines. The AUDPC and PDI values for resistant check Tetep were found to be 432.70 and 45.22, respectively. Higher AUDPC and PDI values serve as an indication for susceptibility towards the disease reaction. The PIC value for the SSR loci varied from 0.225 to 0.743 with an average value of 0.47. Markers RM336, RM209, RM251 and RM224 were most informative on the basis of their high PIC values. UPGMA clustering based on molecular data and AUDPC were found to be in good agreement with each other. Twenty five germplasm accessions were grouped as common in cluster I of dendrogram generated by all alleles, cluster I of dendrogram constructed by Tetep specific alleles, and clusters I and II of the AUDPC dendrogram. Multiple regression analysis revealed that the two markers RM251175 and RM257150 may be considered as markers for association with low disease index (resistance to sheath blight) in rice. Amongst the germplasm accessions, IC383396 and IC426017 behaved as potentially resistant to sheath blight.