Potyviridae as a major challenge to growing cucurbits in Puerto Rico.
Potyviridae causes substantial yield losses in watermelon, pumpkin, zucchini, melon and squash, and are the most frequent family of viruses reported in cucurbits in Puerto Rico. Sampling conducted between 2006 and 2011 showed that PRSV (Papaya ringspot virus) and ZYMV (Zucchini yellow mosaic virus), both transmitted by aphids, are the most frequent virus species infecting various cucurbit species and the invasive species SqVYV (Squash Vein Yellow Virus), transmitted by whitefly, is severely affecting watermelons. The presence of wild cucurbit species provides a constant source of inoculum to crops and vice-versa. The most common wild cucurbit species in Puerto Rico, balsam pear (Momordica charantia L.) can be found everywhere on the island. West Indian gherkin (Cucumis anguria L.) and hedgehog gourd (Cucumis dipsaseus Ehrenb. ex Spach), are more frequently found at lower elevations. ELISA, immunostrip tests, RT-PCR and sequencing of a coat protein gene fragment were conducted to identify and characterize viruses affecting cucurbits. Mechanical transmission to Cucurbita moschata 'Waltham' was conducted and symptoms were evaluated in order to select virus isolates to challenge resistant lines of C. moschata. The different virus isolates induced a broad range of symptoms to inoculated C. moschata, indicating their high biological variability, which was confirmed by the genetic diversity of their sequences. More than one virus or strain usually infects cucurbits and their potential interaction is an additional challenge to cucurbit breeding programs.