PS 59-1
Association of crop density with temperature or precipitation rates determine virus occurrence in Momordica charantia
The relationship between viruses and plants is complex. Yet understanding this interaction in wild plants has been a challenge, which now can be approached with various innovative techniques. The occurrence of plant viruses is affected by both environmental and anthropomorphic factors, such as climatic variables and the proximity of roads, ports and crops. Papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus (ZYMV) are the most commonly encountered potyviruses in cucurbits of Puerto Rico. Here we report on the natural occurrence of these viruses in bitter gourd, Momordica charantia (Cucurbitaceae), a widespread, non-indigenous invasive vine. We examined whether viral infections are associated with disease symptoms and whether infected plants are spatially associated with particular environmental variables. We sampled 347 M. charantiaacross Puerto Rico including adjacent islands of Culebra and Vieques. To detect the viruses, we used an enzyme-linked immunosorbent assay (ELISA) and corroborated the occurrence with RT-PCR. GPS coordinates and altitude were recorded for each sample to produce a map of both symptomatic and asymptomatic plants. Environmental variables including climate and human-related factors were examined in a GLM as variables explaining the virus occurrence and distribution.
Results/Conclusions
While the frequencies of serological detection of viruses were significantly associated with the presence of symptoms (χ2 = 10.5, 1 df, P <0.00025), more than half of the positive samples showed no symptoms and 11% of symptomatic plants were negative for both ZYMV and PRSV. The presence of the potyviruses in M. charantia was related to climatic variables (temperature and precipitation and to density of cucurbit farms. Specifically, the presence of these potyviruses was positively related to farm density when interacting with maximum temperature and annual precipitation (P < 0.05). On the other hand, the presence of the virus was negatively related to farm density when interacting with minimum temperature (P < 0.05). The presence of the viruses was not related to elevation and road density. Further analyses should explore to what degree the selected variables differ in importance across the island. The virus source-sink dynamics between natural reservoirs and cucurbit farms need further work to be clarified.