Fusarium oxysporum f. sp. vasinfectum Identified on Okra in South Carolina, United States

Fusarium oxysporum f. sp. vasinfectum, the causal agent of Fusarium wilt on okra, was recovered in August 2020 on a commercial farm in South Carolina from cultivar Clemson Spineless, an heirloom cultivar still widely grown throughout the southeastern United States. An isolate recovered from discolored vascular tissue in the stem of a diseased plant was identified as F. oxysporum f. sp. vasinfectum based on sequences of the translation elongation factor 1-alpha and beta-tubulin genes. Two inoculation techniques were compared, injecting microconidia into stems and drenching microconidia around the base of plants. Drenching was a significantly more effective inoculation technique than stem injection (P < 0.05), with 77% and 40% of inoculated plants showing vascular discoloration and 73% and 45% of inoculated plants yielding colonies of F. oxysporum when pieces of vascular tissue were cultured on Komada's medium, respectively. This study provides the first confirmation of the presence of F. oxysporum f. sp. vasinfectum on okra in South Carolina.