The 2012 ASHS Annual Conference

 Blackberry yellow vein disease (BYVD), is the most important virus disease of blackberry, especially in fresh blackberry production areas of the southern United States. BYVD is caused by virus complexes, where two or more viruses are needed to induce symptoms. More than fifteen viruses are found associated with BYVD; however, Blackberry yellow vein associated virus (BYVaV) is the most prevalent virus in BYVD plants being detected in more than 50% of the samples exhibiting typical disease symptoms. Blackberry chlorotic ringspot virus (BCRV) is another virus frequently found in BYVD plants, and in addition to blackberry, can also infect rose and raspberry. Despite the importance of the viruses as major components of BYVD both are grossly understudied. This study was conducted to better understand the epidemiology of the two viruses that included population diversity, modes of transmission, and potential alternate hosts. The nucleotide sequences of four different genomic regions of 34 isolates of BYVaV were studied to determine the variability within virus population. RNA 3 of more than 30 BCRV isolates was used in this diversity study. Selection pressure on six coding regions of BYVaV and the coat protein and movement protein of BCRV was evaluated. Two whitefly species were tested for their ability to transmit BYVaV and seed transmission assays for BCRV were performed on three hosts. In addition, 25 plant species were tested as potential alternative hosts of the two viruses. The BYVaV population was fairly diverse, unlike BCRV US-isolates, but yet all coding regions for both viruses were under purifying selection. The greenhouse and banded-winged whiteflies were identified as efficient vectors of BYVaV and BCRV was found to naturally infect apple and be seed transmissible in all the three hosts tested.