Foundation Plant Services has teamed with UC Cooperative Extension advisor Scott Stoddard to conduct virus testing as part of an NCPN-SP supported economic study. The study aims to identify the impact of specific virus diseases on sweetpotato production in California. Field trials began in 2021, comparing old to new (G1) seed for virus infection and yield. In 2021 and 2022, no special measures were done in the field after transplanting to keep the plants free of aphids, the primary vector for the four viruses that infect sweetpotatoes (SPFMV, SPV2, SPVC, SPVG). In 2021, there was a 50% to 92% increase in total marketable yield with G1 compared to old seed. In 2022, yields increased 0 - 20%. Just as importantly, skin color and overall appearance of the harvested roots were superior in G0 and G2 plants.
In 2021, pre- and post-harvest testing of the seed roots (assessed by RT-PCR and RT-qPCR) showed an increase in virus accumulation with age: 57% of the G1 roots were found to have only one of the four viruses, while G2 seed was found to be nearly 100% infected with all four. G0 plants, which were virus tested and only grown in the FPS screened greenhouse, were also found to be nearly 100% infected, which suggests that even the cleanest plants can become infected with viruses in one growing season.
As part of the USDA-SCRI CleanSEED project, this trial was conducted again in 2023 using G0 greenhouse plants, and G1 and G6 seed for the variety Beauregard, and G1, G2, and G3 seed for the variety Covington. For this project, the field plots were separated by clean cultivated borders and by growing peanuts on adjacent beds to act as a trap crop to suppress plant-to-plant transmission of viruses by aphids. Total marketable yield was improved 16 – 22% depending on variety, with the largest impacts on jumbo root production. Virus results are pending.
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