Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2009
Publication Date: 9/1/2009
Citation: Liu, G., Jia, Y., Correa-Victoria, F.J., Prado, G.A., Yeater, K.M., McClung, A.M., Correll, J.C. 2009. Mapping quantitative trait loci responsible for resistance to rice sheath blight disease using greenhouse assays. Phytopathology. 99(9):1078-1084. Interpretive Summary: Rhizoctonia solani is the pathogen causing significant crop damages on many crops including rice, wheat and soybeans. The group AG1-IA is the casual agent for the most widespread and damaging rice sheath blight diseases worldwide. In the present study, two greenhouse phenotyping methods, microchamber (MCCM) and mist chamber (MCM), were adapted to map the quantitative resistance loci (QTL) using seedlings and young adults of a US adapted indica cultivar, Jasmine 85, initially developed by the International Rice Research Institute. A recombinant inbred line population consisting of 256 F5 individuals of the cross of Lemont with Jasmine 85 was used for this study. The major RSB-QTL qSB9-2 co-segregated with single sequence repeat (SSR) marker RM245 on chromosome 9 was identified to contribute 24.3% of total phenotypic variation using MCCM and 27.2% using MCM. Four QTL or QTL regions on chromosomes 2, 3 and 9 identified in the present study were previously validated by classical field evaluation using different mapping populations. However, five new QTL on chromosomes 1, 3, 5 and 6, previously not reported, were found using the current greenhouse methods. Together, a total of 11 QTL were identified on chromosomes 1, 2, 3, 5, 6 and 9 using MCCM and MCM. These observations suggest that MCCM and MCM are powerful phenotyping tools to accelerate the QTL mapping, and SSR marker RM245 can be used to tag the major effect of QTL in the marker-assisted breeding programs using Jasmine 85.
Technical Abstract: Rice sheath blight (RSB) caused by the soil-borne pathogen Rhizoctonia solani, is one of the most destructive diseases of rice, causing severe losses in yield and quality annually. Quantitative trait loci (QTL) responsible for RSB resistance were analyzed using field phenotypic data in literature reports. In this study, two greenhouse evaluation methods of micro-chamber and mist chamber were used to confirm previously identified RSB-QTL and to detect new RSB-QTL. The disease reactions of 250 F5 recombinant inbred lines (RIL) population from the cross derived from Lemont and Jasmine 85 to RSB were measured using micro-chamber method (MCCM) and mist chamber method (MCM) under greenhouse conditions. A total of 11 RSB-QTL was identified on chromosomes 1, 2, 3, 5, 6 and 9 using MCCM and MCM. qSB1 and qSB9-2 were identified by both MCCM and MCM. The major RSB-QTL qSB9-2 co-segregated with RM245 on chromosome 9 was identified contributing 24.3% of total phenotypic variation using MCCM and 27.2% using MCM. Four RSB-QTL or RSB-QTL regions on chromosomes 2, 3 and 9 were confirmed with the previously reported RSB-QTL, and five new RSB-QTL on chromosomes 1, 3, 5 and 6 were found. These observations suggest that MCCM and MCM are powerful tools for RSB-QTL mapping and RM245 is a robust molecular marker for the marker-assisted breeding programs using Jasmine 85 for improved sheath blight resistance.