H. E. Simmons, Department of Biology, The Pennsylvania State University, University Park, PA 16802;
E. C. Holmes, Department of Biology, The Pennsylvania State University, University Park, PA 16802, and Fogarty International Center, National Institutes of Health, Bethesda, MD 20892;
F. E. Gildow, Department of Plant Pathology, and
M. A. Bothe-Goralczyk and
A. G. Stephenson, Department of Biology, The Pennsylvania State University, University Park, PA 16802
Within two decades of its discovery, Zucchini yellow mosaic virus (ZYMV) achieved a global distribution. However, whether or not seed transmission occurs in this economically significant crop pathogen is controversial, and the relative impact of seed transmission on the epidemiology of ZYMV remains unclear. Using reverse transcription–polymerase chain reaction, we observed a seed transmission rate of 1.6% in Cucurbita pepo subsp. texana and show that seed-infected C. pepo plants are capable of initiating horizontal ZYMV infections, both mechanically and via an aphid vector (Myzus persicae). We also provide evidence that ZYMV-infected seeds may act as effective viral reservoirs, partially accounting for the current geographic distribution of ZYMV. Finally, the observation that ZYMV infection of C. pepo seeds results in virtually symptomless infection, coupled with our finding that an antibody test failed to detect vertically transmitted ZYMV in infected seed, highlights the urgent need to standardize current detection methods for seed infection.