Utilizing immunoassays to determine systemic tomato spotted wilt virus infection for elucidating field resistance in peanut

Abstract

Tomato spotted wilt disease was compared in three peanut cultivars, SunOleic 95R, Southern Runner (S. Runner) and DP-1, at two planting dates (April and May) and row spacings (7.6 and 15.2 cm) in a 2-year study in Florida. Tomato spotted wilt virus (TSWV) was detected directly using an enzyme-linked immuno-sorbent assay (ELISA) in both leaf and root crown tissues throughout the growing season to determine the timing and percentage of infected plants. Under low disease pressure, in harvested samples, more April-planted peanuts were infected with TSWV than May-planted. TSWV infection was not affected by plant spacings regardless of disease pressure. Under low disease pressure, from 60 days after planting (DAP), the most susceptible cultivar, SunOleic 95R, had a significantly higher percentage of plants with TSWV compared to the more resistant cultivars. Under high disease pressure, TSWV infection was detected earlier (30 DAP), and there was a clear separation of cultivars, with SunOleic 95R showing the highest infection (75%) followed by S. Runner (55%) and then DP-1 (20%). A higher incidence of TSWV in root crowns compared to leaves was observed for all cultivars. A delayed accumulation of TSWV in a cultivar was a reliable indicator of resistance. The field resistance manifested by peanut may be due to factors that decrease TSWV systemic spread resulting in slower TSWV accumulation in root crowns.