|Matsumoto Brower, Tracie|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2012
Publication Date: 6/1/2012
Citation: Melzer, M.J., J.S. Sugano, D. Cabanas, K.K. Dey, B. Kandouh, D. Mauro, I. Rushanaedy, S. Srivastava, S. Watanabe, W.B. Borth, S. Tripathi, T. Matsumoto, L. Keith, D. Gonsalves, J.S. Hu. 2012. First report of Pepper mottle virus infecting tomato in Hawaii. Plant Dis. 96(6):917. Interpretive Summary: This is the first report of Pepper mottle virus in Hawaii, and to the best of our knowledge, the first report of this virus naturally infecting tomato in the USA. The virus was confirmed using two different assay methods of sequencing the nucleic acid of the virus product and by using an antibody detection methods specific for the virus. Although plant growth was not noticeably impaired by Pepper mottle virus infection, the majority of fruit from infected plants was unsaleable, making Pepper mottle virus a considerable hindrance to tomato production in Hawaii.
Technical Abstract: In August 2011, tomato (Solanum lycopersicum L.) fruit from a University of Hawaii field trial evaluating varietal resistance to Tomato spotted wilt virus (TSWV) and Tomato yellow leaf curl virus (TYLCV) displayed mottling symptoms similar to that caused by TSWV or other tospoviruses. The foliage from affected plants, however, did not display typical symptoms caused by TSWV and was negative for TSWV using a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and TSWV immunostrips (AgDia, Elkhart, IN) when performed following the manufacturer’s instructions. A reverse-transcription PCR assay using universal tospovirus primers TsMCR2 and 3’T12 (1) amplified a ~550 bp product from the total RNA isolated from symptomatic plants but not healthy plants. This product was larger than the expected product size (350-450 bp) for a tospovirus (1). Surprisingly, following primer sequence trimming, the 517 bp amplification product was found to be 92 to 99% identical to nucleotide positions 4363 to 4879 of Pepper mottle virus (PepMoV; family Potyviridae, genus Potyvirus) sequence accessions in GenBank. To confirm the presence of PepMoV in these samples, the total RNA from a symptomatic and an asymptomatic plant was isolated using a RNeasy® Plant Mini Kit (Qiagen, Valencia, CA) and reverse transcribed using Invitrogen SuperScript® III reverse transcriptase (Life Technologies, Grand Island, NY) and primer 900 [5’-CACTCCCTATTATCCAGG(T)16-3’] following the enzyme manufacturer’s directions. The cDNA was then used as template in a universal potyvirus PCR assay using primers 900 and Sprimer as described (2). A ~1700 bp product was amplified from the cDNA of the symptomatic but not the asymptomatic plant. This product was cloned using pGEM-T Easy (Promega, Madison, WI) and three clones were sequenced at the University of Hawaii’s Advanced Studies in Genomics, Proteomics, and Bioinformatics laboratory. The consensus sequence of the three clones was deposited in GenBank (accession JQ429788) and found to be 96 to 97% identical to positions 7917 through 9640 of other PepMoV accessions in the database. To determine the incidence of PepMoV in the field trial, after 10 weeks in the ground all 292 plants representing 14 tomato varieties were assayed for the virus using a PepMoV-specific DAS-ELISA (AgDia) following the manufacturer’s directions. Plants were considered positive if their mean absorbance at 405nm was greater than the mean absorbance + 3 standard deviations + 10% of the negative control samples. The virus incidence ranged from 4.8 to 47.6% for the different varieties, with an overall incidence of 19.9%. Although plant growth was not noticeably impaired by PepMoV infection, the majority of fruit from infected plants was unsaleable, making PepMoV a considerable hindrance to tomato production in Hawaii. PepMoV has been reported to naturally infect tomato in Honduras (3) and South Korea (4). This is the first report of this virus in Hawaii, and to the best of our knowledge, the first report of this virus naturally infecting tomato in the USA.