Zuo, S., Yin, Y., Zhang, L., Zhang, Y., Chen, Z., Gu, S., Zhu, L. and Pan, X. 2011. Effect and breeding potential of qSB-11^LE, a sheath blight resistance QTL from a susceptible rice cultivar. Can. J. Plant Sci. 91: 191-198. Sheath blight (SB) caused by Rhizoctonia solani is one of the most important diseases of rice worldwide. The QTL qSB-11^LE, located on chromosome 11 of an SB-susceptible Oryza japonica rice cultivar Lemont, was identified in previous studies. In this study, its effect on SB resistance and its potential in breeding programs were evaluated using a set of near-isogenic lines (NILs) that exhibit three different genotypes at the qSB-11^LE locus and seven backcross populations. Results of field disease evaluation under artificial inoculation showed that the inheritance of resistance of qSB-11^LE to SB is controlled by additive gene action and that the genes have a dosage effect on SB resistance. In greenhouse evaluations, the resistance effect of qSB-11^LE was expressed at 11 and 14 d after inoculation at the tillering stage. Analysis of field resistance of six BC₁F₁ populations and one BC₂F₁ population, developed from the backcrosses between Lemont as the donor parent and six commercial O. indica rice cultivars as recurrent parents, indicated that qSB-11^LE could be effectively used to enhance these cultivars' SB resistance. These observations suggest that the qSB-11^LE has considerable potential in rice breeding for resistance to SB, and that its flanking molecular markers could be employed in practical breeding programs for marker-assisted selection.