Submitted to: International Plant Virus Epidemiology Symposium
Publication Type: Proceedings
Publication Acceptance Date: January 20, 2005
Publication Date: April 4, 2005
Citation: Liu, H-Y., Sears, J.L., Lewellen, R.T. 2005. Etiology and pathogenicity studies of resistance-breaking isolates of beet necrotic yellow vein virus.Abstract of IX International Plant Virus Epidemiology Symposium. Page 96. April 4-7, 2005, Lima, Peru. Technical Abstract: Rhizomania is one of the most economically important diseases of sugar beet and is widely distributed in most sugar beet growing areas worldwide. The disease is caused by Beet necrotic yellow vein virus (BNYVV) and vectored by the soil-borne fungus 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 partially resistant sugar beet cultivars with Rz1 allele developed against this devastating disease seem to be compromised. 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 coat protein gene from RNA-2 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.