Evaluation of the effect of qSB-9Tq involved in quantitative resistance to rice sheath blight using near-isogenic lines

Abstract

Can. J. Plant Sci. 89: 731-737. Resistance to rice sheath blight disease that causes significant yield losses worldwide is controlled by multiple quantitative trait loci (QTL). The accurate resistance effect of qSB-9 Tq, a major QTL that derived from the indica cultivar Teqing, was investigated by using a backcross population of Teqing and Lemont (the latter as the recurrent parent) and a set of near-isogenic lines (NIL) developed in this study. A strong pathogenic Rhizoctonia solani line, RH-9, was used for inoculation. Two different experimental designs were adopted. One was a completely randomized experiment in which plants that exhibited three different genotypes at qSB-9Tq locus were distinguished by detecting the marker genotypes flanking qSB-9Tq in the BC6F2 segregation population. The other was a randomized block design experiment with three replicates using the three NILs of qSB-9Tq. The combined results of the two experiments suggested that qSB-9Tq was a dominant resistance QTL and could reduce disease rating by approximately 1.0 using a 0̃9 disease rating scale. The results of the study provide a strong foundation for the fine mapping of qSB-9Tq and its utilization in breeding.