Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2002
Publication Date: N/A
Technical Abstract: Rice sheath blight, caused by the fungal pathogen Rhizoctonia solani (AG1- IA), is an economically important disease in the United States. The pathogen has a broad host range and no complete resistance genes have been identified from cultivated rice. To identify the sheath blight resistance gene(s) an extensive cytological and molecular characterization of the pathogen has been initiated. A side range of pathogen isolates was collected from rice, barnyardgrass and corn from the state of Arkansas. To facilitate the molecular analysis a differential cultivar screening technique was developed using an in vitro seedling infection with R. solani. The cultural characteristics, anastomosis grouping and infection structure formation of the pathogen were analyzed DNA primers from unique regions within the ribosomal DNA (rDNA) transcribed spacer have been used for a phylogenetic analysis of the selected isolates. Polymerase chain reaction 9PCR) has been used to amplify the fungal genomic DNA using rDNA specific primers. The sequences of amplified PCR products have been determined using ABI-PRISM BigDyeTM Terminator Cycle Sequencing on ABI 377. Three individual transformants from each isolate have been sequenced from both directions using T7 and SP6 primers. Resulting sequences have been confirmed using another set of M13 (forward/reverse) primers. The sequence data have been analyzed using InforMax Vector NTI Suite system. A phylogenetic relationship of R. solani isolates that threaten the U.S. rice industry was determined. The preliminary data provide a better understanding of the molecular evolution of the sheath blight pathogen and this information will be useful in exploring the way to engineer a novel resistance.