Infection dynamics of potato virus Y isolate combinations in three potato cultivars

Authors: MONDAL, SHAONPIUS - Oak Ridge Institute For Science And Education (ORISE); Wintermantel, William - Bill; Gray, Stewart

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2022
Publication Date: 1/1/2023
Citation: Mondal, S., Wintermantel, W.M., Gray, S.M. 2023. Infection dynamics of potato virus Y isolate combinations in three potato cultivars. Plant Disease. 107(1):157-166. https://doi.org/10.1094/PDIS-09-21-1980-RE.
DOI: https://doi.org/10.1094/PDIS-09-21-1980-RE

Interpretive Summary: The United States potato industry has experienced a strain shift in Potato virus Y (PVY); recombinant PVY strains (PVYNTN, PVYN:O) have emerged as the predominant strains over the long dominant ordinary strain (PVYO). The tuber necrotic recombinant strain, PVYNTN, has recently been reported to infect the same epidermal leaf cells along with ordinary strain PVYO in Samsun NN tobacco. To understand mixed infection dynamics in potato plants and daughter tubers, we manually inoculated Red Maria, Cal White, and Pike potato plants either at pre- or post-flowering stage with all possible combinations of two PVYO and two PVYNTN isolates. Samples from systemically infected leaves were collected from different positions on the inoculated plants at different time points in order to quantify virus composition. Tubers were collected for three successive generations in order to determine transmission of each virus isolate through each generation (vertical transmission). PVYNTN outcompeted PVYO at nearly all of the later time points in Pike plants. The strains were equal or nearly equal in Red Maria and Cal White potato early when inoculated pre-flower, but PVYNTN dominated at later stages and in all plants inoculated post-flowering. Tuber yield was greater in plants inoculated post-flowering. Both isolates were transmitted vertically to daughter plants regardless of inoculation time. Relative titers of PVYNTN and PVYO at the later stages of mother plant development were indicative of their relative titers in the daughter plants. The overall dynamics of mixed infections differs among cultivars and virus isolates, but both strains were transmitted from mother to daughter plants, hence keeping both isolates in the next generation plants.

Technical Abstract: The United States potato industry has experienced a strain shift for Potato virus Y (PVY); recombinant PVY strains PVYNTN, PVYN:O) have emerged as the predominant strains over the long dominant ordinary strain (PVYO). Tuber necrotic recombinant strain, PVYNTN, has recently been reported to co-localize and compete with ordinary strain PVYO within single epidermal leaf cells of Samsun NN tobacco. To understand mixed infection dynamics in potato plants and daughter tubers, Red Maria, Cal White, and Pike potato plants were mechanically inoculated either at pre- or post-flowering stage with all possible heterologous isolate combinations of two PVYO and two PVYNTN isolates. Following inoculation, samples from systemically infected leaves were collected from different positions on the plant at different time points and virus composition was quantified by quantitative-TAS-ELISA. Tubers were collected for three successive generations and tested to determine vertical transmission of each virus isolate. Although PVYNTN outcompeted PVYO at nearly all of the later time points in Pike plants, isolates of both strains were equal or nearly equal in competition for Red Maria and Cal White potato early in the infection when inoculated pre-flower, but PVYNTN dominated at later stages and in plants inoculated post-flowering. Tuber yield was greater in plants inoculated post-flowering, but regardless of inoculation time, both isolates were transmitted vertically to daughter plants. The relative titer of PVYNTN and PVYO isolates at the later stages of mother plant development was indicative of what was found in the daughter plants. The overall dynamics of mixed infections differs among cultivars and virus isolates, but it does not change the vertical transmission outcome, hence keeping both isolates in the next generation plants.