Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2005
Publication Date: 7/20/2005
Citation: Vallad, G.E., Qin, Q.M., Grube, R., Hayes, R.J., Ryder, E.J., Subbarao, K.V. 2005. Identified resistance in lettuce germplasm to verticillium wilt caused by verticillium dahliae. Hortscience. v. 40. p. 1109. Interpretive Summary: N/A
Technical Abstract: Since its appearance in 1995, Verticillium wilt of lettuce has spread to several production areas in the Salinas River Valley where nearly 60% of California's lettuce acreage is located. A replicated field trial was conducted to assess various modern and heirloom lettuce (Lactuca sativa) cultivars and plant introduction lines and L. virosa lines for resistance to Verticillium wilt. Based on horticultural type, lettuce plants were destructively sampled at harvest maturity and assessed for the incidence of Verticillium wilt. Of the L. sativa cultivars, only the iceberg type displayed pronounced foliar symptoms of stunting and wilting. Disease incidence based on root symptoms ranged from 0% to 100%, with continuous variation found across and within lettuce types. Most cos, crisphead and leaf cultivars exhibited 20% or greater disease incidence. Butter cultivars exhibited the lowest disease incidence among the major horticultural lettuce types examined, and Latin and Batavia type cultivars exhibited the lowest disease incidence overall. Disease progression was further monitored for 10 select lettuce cultivars for two weeks past harvest maturity. Disease intensity increased over the two week period for some cultivars, demonstrating the need to assess plants for Verticillium wilt past harvest maturity to avoid misclassifying plants. The L. sativa plant introduction lines tested, predominantly stem and oil-seed horticultural types, were quite susceptible and exhibited distinct symptoms of wilt and defoliation possibly due to their elongated growth habit. The variation in disease incidence among the L. virosa lines tested was discontinuous, with discrete differences in susceptibility. Overall, the results reflected trends found in previous greenhouse and field trials.