LAUSR

Isolates of Tomato yellow leaf curl virus (TYLCV) species (genus Begomovirus, family Geminiviridae) infect tomato crops worldwide causing severe economic damage. Members of the whitefly Bemisia tabaci sibling species group are the vector of begomoviruses, including TYLCV. However, transmission of isolates of the type (Israel, IL) strain of TYLCV (TYLCV-IL) by tomato seeds has recently been reported based on infections occurring in Korea. Because of the consequences of this finding on the epidemiology and control of the disease caused by TYLCV and on the seed market, it was considered essential to revisit and expand those results to other tomato-growing areas. TYLCV DNA content was detected in tomato and Nicotiana benthamiana seeds collected from plants naturally or experimentally infected with TYLCV-IL supporting seed borne nature. The TYLCV-IL replication detected in tomato and N. benthamiana flower reproductive organs demonstrated close association of this virus with the seeds during maturation. However, the significant reduction of TYLCV DNA load after surface disinfections of tomato seeds suggests that most of the virus is located externally, as contaminant of the seed coat. Transmission assays, carried out with seven tomato genotypes and more than 3000 tomato plants revealed no evidence of seed transmission from "surface disinfected" or untreated seeds for two Mediterranean isolates of TYLCV-IL. Similar results were also obtained for seeds collected from TYLCV-IL-infected N. benthamiana plants. The results support that TYLCV-IL is seed-borne but is not seed-transmitted in tomato or N. benthamiana suggesting that transmission through seeds is not a general property of TYLCV.