GENOMIC CHARACTERIZATION OF RICE GERMPLASM
Location: Dale Bumpers National Rice Research Center
Title: Identification of Sheath Blight Resistance QTLs in Rice Using Recombinant Inbred Line Population of Lemont X Jasmine 85
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2008
Publication Date: March 1, 2008
Citation: Liu, G., Jia, Y., Correa, F., Jia, M.H., McClung, A.M., Groth, D., Correll, J.C., Rutger, J.N. 2008. Identification of sheath blight resistance QTLs in rice using recombinant inbred line population of Lemont X Jasmine 85. In: Proceedings of the 32nd Rice Technical Working Group Meetings, February 18-21, 2008, San Diego, CA. 2008. CDROM.
Rice sheath blight (RSB) caused by the soil borne pathogen Rhizoctonia solani, is one of the most destructive diseases of rice around the globe, causing severe losses in rice yield and quality annually.
Major gene(s) governing the resistance to RSB have not been found in cultivated rice worldwide. However, the different resistance reactions of rice cultivars to RSB have been well documented. Several phenotyping methods for evaluating disease reaction to RSB, such as “Tooth pick method” and “Inoculum injection”, have been applied to map the quantitative trait loci (QTLs) of RSB resistance using molecular markers of restricted fragment length polymorphism (RFLP) and simple sequence repeat (SSR) markers. The QTLs responsible for RSB resistance have been commonly found on rice chromosomes 3, 9 and 11. Fine mapping of these QTLs will facilitate marker-assisted selection in rice breeding programs.
One goal of the RiceCAP project is to develop user-friendly molecular methods to tag resistance to RSB to improve breeding efficiency. Jasmine 85, identified as having strong resistance to RSB in both seedling and adult stages using micro-chamber and field methods, is being used as the donor for genetic resistance to RSB. After infecting Jasmine 85 with the sheath blight pathogen, 400 highly induced and 400 differentially induced genes have been isolated using Robust-Long Range Serial analysis of Gene Expression and DNA microarray. Their mapping position in silico has been constructed for fine mapping onto the genetic map of SB-QTL using Jasmine 85.
So far, we have improved a micro-chamber screening method that was originally used by rice breeders in Bangledesh and observed by Dr. Shannon Pinson to evaluate the RSB resistance of seedlings at 3-4 leaf stage in greenhouse. In addition, a mist chamber method routinely used by breeders in Colombia has been used to evaluate adult plant resistance in the greenhouse allowing us to verify the genetic resistance identified by the micro-chamber.
These methods have been used as an effective approach to accurately quantify the resistance to RSB in this study. Thus far, the disease reactions of 250 recombinant inbred lines (RILs) of the Lemont X Jasmine 85 F5 population to RSB were evaluated in a greenhouse at CIAT, Colombia using both micro-chamber and mist chamber methods. The F5 RIL population has been genotyped using more than 200 SSR markers. The first genetic linkage map is being constructed, and progress in the identification of the novel QTLs in controlling RSB in JSMN will be presented.