Effect of Tomato Spotted Wilt Tospovirus (TSWV) Infection on the Fruits of Tomato (Lycopersicon esculentum) Plants of Cultivars Carrying the SW-5 gene

Peculiar necrotic ring spots on tomato fruits from TSWV! resistant plants containing SW!4 gene that occur in _eld conditions are caused by feeding of viruliferous thrips as shown by transmission assays conducted in controlled conditions[ The ring spots are caused by a progressive TSWV infection probably due to insu.cient hyper! sensitive response as a consequence of the presence of the SW!4 gene[ These diseased fruits appeared 4 weeks later than typical symptoms of TSWV infection on leaves of susceptible plants in a comparative study performed in an early!transplanted tomato _eld[ The percentage of susceptible tomato hybrids infected by TSWV was approximately 03)\ whereas only 3) of symptom!free plants of TSWV!resistant hybrids showed some diseased fruits[ Only 00) of the fruits of these plants were infected[ These results could change depending on the feeding behaviour and the proportion of viruliferous thrips in the thrips population during the early stages of fruit development[ Changes in management practices in tomato crops conducted to reduce their populations at this time of the season could decrease the number of unmarketable fruits[ The presence of TSWV!resistant plants showing a systemic infection in open commercial tomato _elds with higher proportions than expected is discussed[