EVALUATIONS OF DIFFERENTIAL ACQUISITION AND TRANSMISSION OF BNYVV BY POLYMYXA BETAE ISOLATES FROM THROUGHOUT THE UNITED STATES Project Leader: William M. Wintermantel, Research Plant Pathologist Collaborator:

Background: Polymyxa betae is the vector of several soil-borne viruses of sugarbeet (Abe and Tamada 1986, Liu and Lewellen 2008, Wisler et al. 1994, Kaufmann et al. 1992), including Beet necrotic yellow vein virus (BNYVV), the cause of rhizomania (Tamada and Baba 1973). BNYVV is transmitted by zoospores of this fungus-related microorganism that swim in water films and infect feeder roots of sugarbeet plants. P. betae is an obligate parasite and is found in virtually every soil in which sugarbeet is grown (Liu and Lewellen 2007). The pathogen forms long-lived resting spores clustered together to form cystosori (Fig. 1) that can survive in the field for many decades. The life cycle and mode by which P. betae infects sugarbeet roots are well documented (Keskin 1964). P. betae is usually not considered to cause measurable damage to sugar beet, however, in controlled tests, it has been shown to cause reductions in yield (Wisler et al 2003, Liu and Lewellen 2008), and studies have shown that nearly half the protein changes identified in sugarbeet associated with BNYVV infection were induced by the presence of P. betae in roots (Larson et al., 2008).