a. r. afsharifar

Tomato leaf curl disease (TLCD) is one of the most destructive diseases of tomato caused by a number of begomoviruses including Tomato yellow leaf curl virus (TYLCV) belonging to the genus Begomovirus (family Geminiviridae). TYLCV is transmitted by the whitefly Bemisia tabaci. In order to investigate changes in occurrence and severity of TLCD and evaluate the viral vector population on three tomato cultivars namely Yellow Round Multiple Truss (YRMT), PANDA F1 and Black Russian ST 175 (BRST) in a greenhouse in College of Agriculture, Shiraz University, 45 plants (15 plants from each cultivar) were randomly selected. Specific primers of an Iranian isolate of TYLCV (TYLCV[Ab])were used to detect plants naturally infected with TYLCV by PCR. After symptom emergence, both disease incidence (DI) and severity (DS) were evaluated visually using an ordinal rating scale. To estimate vector’s population, 50 whitefly puparia were collected from two leaves of each cultivar and based on the vasiforme and outward specifications of puparia, B. tabaci distinguished from Trialeurodes vaporariorum. The data analysis by SAS software indicated significant differences in DI, DS and vector population dynamics between three tomato cultivars. The DI was estimated to be 6.6% to 86.6%, at 40 and 100 days after planting date, respectively. The incidence and severity of disease and insect vector populations in YRMT and PANDA-F1 cultivars showed a higher trend and rose more sharply compare to those in the BRST cultivar. BRST was comparatively more resistant than the two other cultivars (YRMT and PANDA) which were susceptible to TYLCV.