Spatial analysis of occurrence of PRSV and ZYMV, two aphid-transmitted viruses, in Momordica charantia in Puerto Rico

Viruses infecting plants may cause large economic losses worldwide but the relationship between viruses, plants and environment is still not clear.  Not only virus-plant-environment interactions but also the impact of viruses of cultivated crops introduced into natural environments has received limited attention. In order to develop efficient strategies for crop protection, the diversity of viruses in non-cultivated plants, virus reservoirs, needs to be understood. This work focuses on the natural occurrence in Momordica charantia (Cucurbitaceae), a wild naturalized invasive vine, of the two main potyvirus reported for cucurbits in Puerto Rico.  We sampled 347 M. charantia plants across Puerto Rico including adjacent islands of Culebra and Vieques.  We used an enzyme-linked immunosorbent assay (ELISA) for detection of potyviruses and RT-PCR to amplify the CP region using MJ1 and MJ2 primers.  Plotting the species occurrence according to a model developed in a Geographic Information System produced maps of both symptomatic and asymptomatic plant predicted distributions. Environmental variables including climate and human-related factors were examined as potential drivers of virus occurrence. The viruses Papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus (ZYMV) were the most commonly encountered potyviruses.  The presence of symptoms in Momordica was closely associated with the presence of both viruses.  The distribution of PRSV, ZYMV and symptoms (found in Momordica) is discussed in relation to both climate and human–related variables.  Our comprehensive approach to the study of virus-plant interactions highlights the need to include large-scale variables in the study of virus-plant interactions. This study provides insights into the interactions of virus with cultivated plants non–cultivated plants and environmental factors.