Cucurbit Leaf Crumple Virus (CuLCrV) is Seed Transmitted in Yellow Squash (Cucurbita pepo L.).

ABSTRACT

The traditional understanding of begomovirus transmission exclusively through the whitefly Bemisia tabaci (Gennadius) has shifted with findings of seed transmission in some begomoviruses over the last decade. We investigated the seed transmissibility of cucurbit leaf crumple virus (CuLCrV), a bipartite begomovirus that has recently emerged as a severe constraint for yellow squash (Cucurbita pepo L.) production in the southeastern United States. We found high concentration of CuLCrV in male and female flower tissues of infected squash, including pollen and ovules. The virus infiltrated the fruit tissues including the endocarp and funiculus, which are anatomically positioned adjacent to the seeds. In seeds, CuLCrV was detected in the endosperm and embryo where there are no vascular connections, in addition to the seed coat. The virus was detected in the radicle, plumule, cotyledonary leaves, and true leaves of seedlings grown from seeds collected from infected fruits. In the grow-out test conducted, CuLCrV infections ranged from 17-56% of the progeny plants. To ensure that partial viral genome fragments were not being mistaken for replicative forms of the virus, we performed RCA ̶ PCR and amplified complete DNA-A and DNA-B of CuLCrV from seed tissues, seedlings, progeny plants of CuLCrV infected squash. Near complete DNA-A and DNA-B sequences of CuLCrV were recovered from a progeny plant, further validating our findings. Our results demonstrate that CuLCrV can translocate from vegetative to reproductive tissues of yellow squash, persist within the seeds, and subsequently induce infection in progeny plants, confirming its capacity for seed transmission.