Etiology of tomato plant decline in the California desert

Tomato plant decline (TPD) has been a limiting factor in the production of fresh market tomatoes in the desert areas of California since 1977. Diseased plants are characterized by stunting, leaf rolling, and leaflet chlorosis. The disease occurs only in fields with a history of previous tomato crops and can reduce yields by as much as 80%. Although TPD is known to be soilborne, the cause of the disease has not been determined until now. Tomatoes grown at 14 C in soil collected from a field with a history of TPD became infected with a tombusvirus that was serologically indistinguishable from the BS-3 strain of tomato bushy stunt virus (TBSV). When tomato debris infected with TBSV was used to infest soil, seedlings planted in this soil developed symptoms of TPD and were positive for TBSV infection if grown at 16 C. In addition, TBSV was consistently found associated with field-grown, symptomatic plants collected during 1987 and 1988, as determined by ELISA. Eight tomato cultivars, which in field observations were considered to be susceptible or tolerant to TPD, were mechanically inoculated with TBSV and grown in the greenhouse. The symptoms were most severe on the TPD-susceptible plants, but were mild on TPD-tolerant plants. Symptom development was also found to be dependent on temperature in a manner consistent with temperature sensitive replication of the virus. These experiments implicate TBSV as the etiological agent of TPD