First Report of Lettuce Chlorosis Virus Naturally Infecting Sugar Beets in California

Sugar beet (Beta vulgaris) plants showing interveinal yellowing and thickened leaves were collected from two fields in Imperial County, CA, for disease assessment in January 1996. Yellowing symptoms were widespread in these fields during the winter of 1995 to 1996. Initial enzyme-linked immunosorbent assays (ELISA) with polyclonal antiserum (ATCC) for beet western yellows virus were consistently negative. Inoculations with Bemisia tabaci "B" biotype (B. argentifolii) whiteflies onto the indicator plants Chenopodium capitatum, C. murale, lettuce (Lactuca sativa), and sugar beet resulted in interveinal yellowing, reddening, and thickened leaves characteristic of whitefly-transmitted closteroviruses (1). Western blot (immunoblot) analyses were performed with antisera to the purified virions of lettuce chlorosis virus (LCV) and lettuce infectious yellows virus (LIYV). Tissue extracts from original beet plants representing two fields and from all subsequent whitefly-inoculated indicator plants consistently showed a single band at ca. 32 kDa, reported to be the molecular mass for LCV capsid protein. Corresponding Western blot analyses for LIYV with the same tissue extracts were negative. No reactions were observed in Western blot assays with tissue extracts from healthy plants. Although sugar beet is a host for LCV as shown by laboratory experiments (1), this is the first report of a natural infection of LCV in sugar beet. Reference: (1) J. E. Duffus et al. Eur. J. Plant Pathol. 102:591, 1996.