Spatial and temporal analysis of squash vein yellowing virus infections In watermelon

Authors: Turechek, William; ROBERTS, PAMELA - University Of Florida; STANSLY, PHILIP - University Of Florida; Webster, Craig; Kousik, Chandrasekar - Shaker; Adkins, Scott

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2014
Publication Date: 8/1/2014
Publication URL: http://dx.doi.org/10.1094/PDIS-10-13-1094-RE
Citation: Turechek, W., Roberts, P.D., Stansly, P.A., Webster, C.G., Kousik, C.S., Adkins, S.T. 2014. Spatial and temporal analysis of squash vein yellowing virus infections In watermelon. Plant Disease. 98(12):1671-1680. https://doi.org/10.1094/PDIS-10-13-1094-RE.
DOI: https://doi.org/10.1094/PDIS-10-13-1094-RE

Interpretive Summary: Squash vein yellowing virus (SqVYV), Cucurbit leaf crumple virus (CuLCrV), and Cucurbit yellow stunting disorder virus (CYSDV) are three whitefly-transmitted viruses recently introduced to Florida. The epidemiology of these three viruses was studied in a one hectare field of watermelon over six growing seasons (I–VI) to characterize the spatial patterning of disease, temporal rate of disease progress, and association among viruses. Results showed that disease progressed in a characteristic logistic fashion (S-shaped curve) for SqVYV and CuLCrV. SqVYV and CuLCrV displayed significant but variable levels of aggregation in the field and an association analysis indicated that the viruses were largely transmitted independently. Limited information was gathered for CYSDV because it appeared in only season during the study. Results of this study provide the necessary information to allow the development of a sampling procedure and other predictive models for SqVYV-induced vine decline, but are likely of limited use for CuLCrV and CYSDV because the development on watermelon was affected by the severity of SqVYV epidemics.

Technical Abstract: Squash vein yellowing virus (SqVYV), Cucurbit leaf crumple virus (CuLCrV), and Cucurbit yellow stunting disorder virus (CYSDV) are three whitefly-transmitted viruses recently introduced to Florida that induce visually distinguishable symptoms on watermelon. The epidemiology of these three viruses was studied in a one hectare field of ‘Fiesta’ watermelon over six growing seasons (I–VI) to characterize the spatial patterning of disease, temporal rate of disease progress, and association among viruses. During each season, the field was scouted every 7-14 days for the incidence of virus and number of whiteflies starting at transplanting and continuing until harvest or until all plants collapsed from SqVYV-induced vine decline. The incidence of SqVYV reached 100% during seasons I, II and V, and 20% during season III. SqVYV did not occur during seasons IV and VI. The incidence of CuLCrV was most severe during season I and was progressively less severe in subsequent seasons. CYSDV was detected only in season V. SqVYV progressed in a characteristic logistic fashion in seasons I, II, and V, but less so in season III. The rate of disease progress, rL, was similar for the three seasons with high disease incidence with an average value of 0.166. Disease progress curves were more flat for both CuLCrV and CYSDV, and rL ranged from 0.07-0.13. All viruses displayed significant but variable levels of aggregation according to their fits to the beta-binomial distribution and ordinary runs analysis. The fit to the binary power law gave slope parameter estimates of 1.156 and 1.053 for SqVYV and CuLCrV, respectively. An association analysis indicated that the viruses were largely transmitted independently. A positive correlation (r = 0.392) between the seasonal mean incidence of SqVYV and mean number of whiteflies was found. Results of this study provide the necessary information to allow the development of a sampling procedure and other predictive models for SqVYV-induced vine decline, but are likely of limited use for CuLCrV and CYSDV because the development on watermelon was affected by the severity of SqVYV epidemics.