INFECTION IN SOYBEANS AND ON MULTIPLE HOST PLANTS IN PUERTO RICO BY AN ISOLATE OF COWPEA MILD MOTTLE VIRUS.

Abstract

Seed companies in the USA grow winter soybean (Glycine maxL. Merr.) nurseries in Puerto Rico to advance their breeding programs and seed increase. However, the soybean nurseries are being threatened by a viral disease that cause stunting, leaf and stem necrosis and shoot wilting that leads to death of the whole plant. In the present study transmission assays were conducted using stem grafting, mechanical inoculation, and whiteflies (WFs), Bemisia tabci (Gennadius). Cultivated and wild host plants infested by WFs were surveyed at Dow AgroSciences Research Station and nearby farms at Santa Isabel, Puerto Rico. Based on previous report in Brazil of similar disease caused by an isolate of Cowpea mild mottle virus(CpMMV), a Carlavirus, these samples were screened for the presence of the Carlavirususing enzyme-linked immunosorbent assays (ELISA) and RT-PCR using Carlavirus-specific primers. The results showed that all the transmission assays expressed the viral symptoms on soybean plants on which the tests were done. Out of the 19 plant species surveyed, 8 species gave positive results for the ELISA test. The RT-PCR also successfully amplified a 300 bp fragment from these ELISA positive samples. Additionally, transmission electron microscopy revealed feather-like aggregates of presumed virions in the cytoplasm, characteristic for many members of the genus Carlavirus. This virus infecting soybean and other plants in Puerto Rico is considered an isolate of the CpMMV. This study underlines the importance of controlling WFs and weed species that serve as reservoirs both for the vectors and the virus. DOI:  http://dx.doi.org/10.17525/vrr.v19i1.101