Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings
Publication Acceptance Date: January 10, 2005
Publication Date: July 1, 2005
Citation: Liu, H., Sears, J.L., Lewellen, R.T. 2005. Biological and molecular analysis of beet necrotic yellow vein virus isolates that overcome the resistance genes. American Society of Sugarbeet Technologists, March 2-5, 2005, Palm Springs, California. p. 189-190. Technical Abstract: Rhizomania is an important virus disease of sugar beet. The disease is caused by Beet necrotic yellow vein virus (BNYVV) and vectored by the plasmodiophorid Polymyxa betae. The disease can only be controlled effectively by the use of resistant cultivars. During 2002 and 2003, several sugar beet fields with cultivars partially resistant to BNYVV grown in the Imperial Valley of California were observed with severe rhizomania symptoms, suggesting that resistance conditioned by Rz1 allele had been compromised. Soil testing with sugar beet baiting plants followed by ELISA tests was used to diagnose virus infection. Resistant varieties grown in BNYVV-infested soil from Salinas, CA were ELISA negative. In contrast, when grown in BNYVV-infested soil collected from the Imperial Valley, CA all resistant varieties became infected and tested positive by ELISA. Based on host reaction, distinct BNYVV isolates have been identified from Imperial Valley soil (IV-BNYVV) by single local lesion isolation. These isolates do not contain RNA-5 as determined by RT-PCR. From the banding patterns of single-strand conformation polymorphism analyses we concluded that the resistance-breaking BNYVV isolates from Imperial Valley had likely evolved from the original existing A-type. The pathogenicity of IV-BNYVV isolates was studied. PCR products of RNA2 coat protein gene and P-25 protein (encoded by BNYVV-RNA-3, involved in symptom expression) of IV-BNYVV isolates were sequenced. Sequence alignments revealed only minor amino acid changes compared to the existing A-type of California BNYVV isolates.