2018 ASHS Annual Conference

In Washington state Verticillium wilt (caused by Verticillium dahliae) negatively affects the productivity of eggplant (Solanum melongena). The pathogen colonizes the roots and vascular system, leading to plant wilting and yield loss. This study, done in 2016 and 2017, evaluated the resistance of susceptible eggplant cv. Night Shadow grafted onto five commercial solanaceous rootstock cultivars, Estamino, Java, Meet, Shield and Survivor, and heirloom tomato, cv. Cherokee Purple, for resistance to Verticillium wilt. The study also included non-grafted rootstocks and scion controls. ‘Shield’ was included only in 2017. The field site was naturally infested with V. dahliae, 28 cfu g^-1 and 5 cfu g^-1 of soil in 2016 and 2017, respectively. Seedlings were splice grafted in a greenhouse, healed, and roots were drenched with 5mL of V. dahliae conidial suspension (8 x 10⁶ conidia per mL in 2016 and 2.35 x 10⁶ conidia per mL in 2017) at the time of transplanting to the field. In 2016, Verticillium wilt incidence and severity were noted near harvest (108 DAT) and were lowest for ‘Night Shadow’ grafted onto ‘Estamino’ and ‘Java’ (severity only) and non-grafted rootstocks ‘Estamino’, ‘Java’, ‘Meet’ and ‘Survivor’ (P = 0.01). In 2017, disease severity near harvest (103 DAT) was least for ‘Night Shadow’ grafted onto ‘Survivor’ and greatest for non-grafted ‘Meet’ (P = 0.04); disease incidence was not significantly different among treatments. AUDPC values were only calculated in 2017 and were least for ‘Night Shadow’ grafted onto ‘Estamino’ and ‘Survivor’. Fruit yield was greatest for ‘Night Shadow’ grafted on ‘Meet’ (p=0.03) in 2016, and in 2017 for ‘Night Shadow’ grafted on ‘Cherokee Purple’ (P = 0.0003) for replicates one and three (these replicates exhibited normal growth). In replicates two and four, where plant growth was stunted due to soil conditions, there was no significant difference in fruit yield among treatments. Our results indicate that different rootstocks may interact uniquely and vary with the level of V. dahliae infestation and environmental conditions in the field.