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Importance of seed as an inoculum source for High Plains Virus in sweet corn

Claudia Nischwitz: Utah State University

<div>High plains virus (HPV) is found in small grains and corn and is commonly transmitted by the wheat curl mite. Seed transmission has been reported but was considered unimportant due to low percentage of infection. In 2016, symptomatic sweet corn was found in fields in Utah with symptoms ranging from chlorotic leaf streaks to stunting and reduced ear set. About four percent of the seedlings showed symptoms within two weeks of emergence in the field. None of the plants died. Yield loss was estimated at 50 percent for the field. Virus testing using ELISA showed that the plants were infected with HPV and confirmed with RT-PCR but no wheat curl mites were found on the plants and the infection pattern in the field was consistent with a seedborne disease. Leftover seed obtained from the grower was tested using ELISA, and 70 percent of the seed tested positive for HPV and was verified with RT-PCR. In greenhouse grow out tests of the contaminated seed, three percent of the seedlings showed chlorotic streaks and stunting after three weeks. The results indicate that seed transmission of HPV can be important and result in high yield losses and that seed testing for HPV should be considered. Additional research is necessary to determine if corn variety or virus strain play a role in its significance.</div>