Distribution and transmission of Iris yellow spot virus

In's yellow spot virus (IYSV), a new tospovirus associated with a disease i n onion (Allium cepa) that is known to growers in Israel as "straw bleachin g," was identified and further characterized by host range, serology, elect ron microscopy, and molecular analysis of the nucleocapsid gene. The transm issibility of IYSV by Thrips tabaci and Frankliniella occidentalis was stud ied. IYSV was efficiently transmitted by T. tabaci from infected to healthy onion seedlings and leaf pieces. Two biotypes of F, occidentalis, collecte d from two different locations in Israel, failed to transmit the virus. Sur veys to relate the incidence of thrips populations to that of IYSV were con ducted in onion fields. They revealed that the onion thrips T. tabaci was t he predominant thrips species, and that its incidence was strongly related to that of IYSV. Forty-five percent of the thrips population collected from IYSV-infected onion and garlic fields in Israel transmitted the virus. IYS V was not transmitted to onion seedlings from infected mother plants throug h the seed, and was not located in bulbs of infected plants.