Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 2, 2002
Publication Date: N/A
Technical Abstract: Sheath blight (SB), caused by the fungus Rhizoctonia solani is a major worldwide disease of rice. Resistance to R. solani is considered polygenic in nature with few accessions able to thwart attack by this pathogen. The objective of this study was to evaluate potential of the Descriminant Analysis (DA) procedure to allocate breeding lines into predefined SB groups. To study genetic and molecular aspects of SB resistance, 314 recombinant inbred lines were produced from SB-susceptible Lemont and resistant Teqing varieties. RFLP markers that best discriminated between contrasting resistant (R) and susceptible (S) groups were identified by stepwise DA selection and used to classify lines into groups by the k-nearest neighbor procedure. The largest phenotypic differentiation between R and S groups (3 standard deviations) resulted in 100% correct classification for all lines using 10 markers, while reduced correct classification was observed (80 percent) with 1 standard deviation. Standard QTL interval analysis applied to the same lines resulted in identification of 14 markers that produced 85 percent correct classification. Both DA and QTL methods identified four identical or closely linked markers (less than 5 cm) on chromosomes 3, 4, and 6. In addition, five new potential markers associated with SB were detected by the DA procedure on chromosomes 1, 2, and 11. These results indicate that the DA procedure can effectively identify molecular markers to allocate recombinant inbred lines into predefined groups for resistance to R. solani. The DA procedure should be considered as a complement to QTL interval and other mapping procedures.