Issue link: http://read.dmtmag.com/i/51841
VINEYARD research at the molecular level and newer technologies for virus detec- tion and identification are helping sort out the classification and epi- demiology of leafroll viruses. International grapevine virus authority Giovanni Martelli of the University of Bari in Italy explained that leafrol l agents belong in the fami ly Closterovidae.One. GLRaV-2 is a species in the genus closterovirus that can induce lea- froll symptoms only as an agent of graft transmission or graft incom- patibility. Eight other GLRaVs are spe- cies in the genus ampelovirus, which by definition are vectored by mealybugs and soft-scale insects. However, all GLRaVs can be graft transmitted. Martelli explained that further studies and premises regarding taxonomy and classifi- cation indicate that the number of GLRaV ampeloviruses may now be reduced to six, or perhaps as low as three. Based on these prem- ises, the three leafroll ampelovi- ruses would be GLRaV-1, GLRaV-3 and GLRaV-4. GLRaV-3 is the most prevalent leafroll virus found in commercial vineyards worldwide. GLRaV-2 is generally the second- most common. Mixed infections of two or more GLRaVs commonly occur, as well as variants or strains of each GLRaV. LEAFROLL IN FINGER LAKES VINEYARDS A leafroll survey was started in 2006 by Cornell University researchers, led by Tim Martinson in New York's Finger Lakes region. Out of 95 hybrid and vinifera blocks, 63 (two-thirds) had some GLRaV-infected vines. One-third of these blocks were classified as having high levels of infec- tion (more than 20% of samples). Insect surveys found low levels of grape mealybugs and two species of soft scale. Tim Martinson of Cornell University led the research team that began survey- ing leafroll in Finger Lakes vineyards in 2006. Photo: Ted Rieger WWW.VWM-ONLINE.COM JAN - FEB 2012 VINEYARD & WINERY MANAGEMENT 71