First Report of Natural Infection of Peanut (Groundnut) by Impatiens Necrotic Spot Tospovirus (Family Bunyaviridae).

Abstract

Impatiens necrotic spot tospovirus (INSV) of the family Bunyaviridae is an important viral pathogen of ornamentals and a major constraint in the greenhouse industry (2). Evidence of natural infection of peanut (groundnut, Arachis hypogaea L.) by INSV was found in samples collected from three sites in Frio County, TX, and one site each in Mitchell and Tift counties, GA, during October 1998. Roots from several plants were tested by enzyme-linked immunosorbent assay for tomato spotted wilt tospovirus (TSWV) and INSV. Symptoms on individual mature plants positive for INSV were the same as those associated with late-season TSWV infections: plants appeared yellow and wilted, internal taproot and crown were necrotic, and plant death resulted (1). At one Texas site, three of five composite samples were positive only for INSV. One composite sample at a second Texas site was positive for both TSWV and INSV. Double infections were found in three of four TSWV-positive samples at a third Texas site. In Mitchell County, GA, three of four samples tested were positive only for TSWV, and one was positive for both TSWV and INSV. In Tift County, GA, 11 of 23 samples tested were positive only for INSV, whereas 4 were positive only for TSWV. Double infections were found in 5 of 23 samples. The presence of INSV in the sample from Mitchell County was verified by immunocapture-polymerase chain reaction (PCR) (4). The apparently low titer of INSV in the doubly infected plant necessitated two cycles of PCR for detection of INSV sequences. A primer pair that can amplify most tospoviruses was used for the first PCR cycle (3). Using the PCR product obtained, a second PCR cycle was performed with one tospovirus-specific and one INSV-specific primer. This approach resulted in a product of the expected size (≈298 bp). The PCR product was cloned in a pGEM-T vector and sequenced. Comparisons indicated the sequence obtained from the infected peanut sample from Georgia was 99% identical to the respective S RNA region from known INSV isolates. Serological and molecular sequence data suggest the peanut samples were infected by INSV. Future surveys and screenings of peanut plants for spotted wilt disease should include a test for INSV.