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The effects of Tomato spotted wilt virus (TSWV) on yield and quality of tomato fruits were studied from May through November of 2004 at the Experimental Field of the Agricultural Faculty of Ondokuz Mayis University, in Samsun province, Turkey. TSWV caused 42.1% and 95.5% reduction in yield and marketable value of tomato, respectively. TSWV infection in tomato crop caused significant (P<0.05) reductions in weight, total number, width and length of the fruits in infected plants. Reductions in yieldcontributing parameters were 26.61% in weight,

To detect cucurbit viruses and determine their incidence, surveys were conducted in 45 fields in 18 villages in Samsun province, Turkey from July to October in 1999 and 2000. Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV), and Cucumber mosaic virus (CMV) were detected in cucurbits after analyzing 165 samples by enzyme-linked immunosorbent assay. WMV, ZYMV, and CMV were detected in 53.9, 38.8, and 20.6% of samples tested, respectively. ZYMV and WMV infections were detected in all cucurbit species, but CMV was not detected in any samples of watermelon and pumpkin.

Summary. Progeny tubers were harvested from plants of five potato cultivars that had been grown in potato mop‐top virus (PMTV) infested soil. The tubers were tested for virus infection by methods based on reverse transcriptase‐polymerase chain reaction (RT‐PCR) or enzyme‐linked immunosorbent assay (ELISA) incorporating monoclonal antibodies. Both RT‐PCR and ELISA detected PMTV in extracts from tuber flesh. However, when the assay results were compared for individual tubers, there was an incomplete correlation between the two methods, and more infected tubers were detected by ELISA than by RT‐PCR. PMTV was detected in some samples but not in others taken from different parts of the same tuber, and this uneven distribution may explain the discrepancy between the results of the ELISA and RT‐PCR tests. Storage of tubers of two cvs at an elevated temperature (20oC) for 4 wk prior to testing, nearly doubled the number of sample sites at which PMTV was detected by ELISA. Such pre‐treatment may improve the accuracy of tuber tests. Most tubers of cvs Saturna and Pentland Crown were symptomlessly infected indicating that PMTV may easily escape detection in tubers of these cvs if tests are based solely on presence of visual symptoms. The application of post‐harvest tuber testing, particularly to cvs that do not display obvious symptoms, and the subsequent elimination of contaminated tubers will help to provide effective control of spread, and the establishment of PMTV at new sites.

A spontaneous deletion in RNA 2 of Potato mop-top virus (PMTV) was identified by RT-PCR. The deletion occurred reproducibly during manual passage of two isolates of PMTV and during fungal inoculation of plants with viruliferous soil. The borders of the deletion were conserved in all instances and sequence analyses showed that a contiguous segment of 2113 nucleotides was deleted internally from the genomic RNA 2, leaving the 5h-and 3h-terminal sequences. RT-PCR experiments also showed that the deletion was present in preparations of PMTV particles.

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