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Title: YELLOW VINE OF WATERMELON AND PUMPKIN IN TENNESSEE

Author
item BOST, S. - UNIV. OF TENNESSEE
item MITCHELL, F. - TEXAS A&M UNIVERSITY
item MELCHER, U. - OKLAHOMA STATE UNIVERSITY
item Pair, Sammy
item FLETCHER, J. - OKLAHOMA STATE UNIVERSITY
item WAYADANDE, A. - OKLAHOMA STATE UNIVERSITY
item Bruton, Benny

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/1999
Publication Date: N/A
Citation: Bost, S.C., Mitchell, F., Melcher, U., Pair, S.D., Fletcher, J., Wayadande, A., Bruton, B.D. 1999. Yellow vine of watermelon and pumpkin in Tennessee. Plant Disease. 83:587.

Interpretive Summary: Yellow vine (YV) is a recently recognized vine decline of cucurbits causing plant yellowing, phloem discoloration, and death of vines as fruit approach maturity. In severely affected fields, YV incidence can range from 50 to 100% with similar yield loss. The disease has been associated with a phloem-limited bacterium for which specific PCR primers have been developed and used to confirm presence of the bacterium DNA. First observed in 1988 in Oklahoma and Texas squash and pumpkin, YV was not detected in watermelon and cantaloupe until 1991. The disease has never been detected in cucumber. Initially, the geographical range of the disease appeared to be generally confined to the Cross-Timbers Region of central and northeastern Oklahoma and north central Texas. In 1997-98, YV was diagnosed in commercial fields of watermelon and muskmelon from east Texas (Post Oak Savannah) and all cucurbit-growing areas of Oklahoma. In summer 1998, we found symptoms similar to those of YV in one watermelon (Hardeman County) and three pumpkin fields (Rhea and Morgan Counties) in Tennessee where the leaves turned yellow and affected plants exhibited phloem discoloration. Estimated incidence of YV ranged from less than 1% to 20% of the plants in affected fields. PCR was performed from all watermelon and pumpkin plants exhibiting phloem discoloration and confirmed the presence of the bacterium associated with yellow vine. The occurrence of YV outside of the Cross Timbers Region, and in a location as distant as Tennessee, suggests that the disease may be much more widespread than previously recognized. Diagnosis and monitoring of YV in all cucurbit growing areas is critical for determining the geographic distribution and losses caused by this emerging disease.

Technical Abstract: Yellow vine (YV) is a recently recognized vine decline of cucurbits causing plant yellowing, phloem discoloration, and death of vines as fruit approach maturity. The disease has been associated with a phloem-limited, walled bacterium belonging to the gamma-3-proteobacteria, for which specific PCR primers have been developed and used in diagnosis. First observed in 1988 in Oklahoma and Texas squash and pumpkin, YV was not detected in watermelon and cantaloupe until 1991. Initially, the geographical range of the disease appeared to be generally confined to the Cross-Timbers Region of central and northeastern Oklahoma and north central Texas. In 1997-98, however, YV was diagnosed in commercial fields of watermelon and muskmelon from east Texas (Post Oak Savannah) and all cucurbit-growing areas of Oklahoma. In late summer 1998, symptoms similar to those of YV were observed in one watermelon (Hardeman County) and three pumpkin fields (Rhea and Morgan Counties) in Tennessee. Estimated incidence of YV ranged from less than 1% to 20% of the plants in affected fields. PCR, performed using the YV-specific primers (2), amplified a band of the expected size (409 bp) from all watermelon and pumpkin plants exhibiting phloem discoloration. In contrast, no bands were amplified from asymptomatic (no phloem discoloration) watermelon or pumpkin. The nucleotide sequence of one DNA fragment amplified from a Tennessee watermelon and pumpkin plant was identical to that of the yellow vine bacterium. The occurrence of YV outside of the Cross Timbers Region, and in a location as distant as Tennessee, suggests that the disease may be much more widespread than previously recognized.