Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2000
Publication Date: N/A
Technical Abstract: Rice wild relatives (Oryza spp.) are an important source of useful genes for cultivated rice improvement. Sheath blight, Rhizoctonia solani and blast, Pyricularia grisea, are the major fungal diseases affecting rice in the US. The objectives of this study were to 1) cross southern U.S. rice cultivars with resistant Oryza spp. to introduce additional sources of sheath blight resistance, 2) determine the amount of sheath blight resistance in the Oryza spp., F1 and BC1 progeny and 3) ascertain if any Oryza spp. and their F2 progeny were resistant to US blast races. Plants were inoculated with R. solani colonized toothpicks for sheath blight inoculations. Infected plants were rated using a scale 0=no infection to 9=severely infected and the lesions were measured. Results indicated Oryza spp. rated resistant or moderately resistant. The progenies tested rated moderately resistant to susceptible. In some cases, it appears partial resistance was being transferred into the cultivated rice parent. Oryza spp. and F2 progeny were inoculated with IB-1, IB-33, IB-49, IC-17, IE-1K, IG-1 and IH-1 and rated as 0=no lesions to 9=large susceptible/dead. Blast screening indicates individual O. nivara accessions and the O. rufipogon accession have resistance to common US blast races. Improved resistance to US blast was found in the F2 progeny with the A-genome accessions but was due to the resistance present in the cultivated rice parent.