Pathogenicity of Fusarium oxysporum f. sp. lactucae in lettuce cultivars at different temperatures

Abstract

Fusarium wilt caused by Fusarium oxysporum f. sp. lactucae Race 1 was first detected in lettuce in the Region of Murcia (Spain) in 2017, in plantations in the northwestern area, where the crop is grown in the summer. In order to establish control strategies against the disease, studies have been carried out under controlled conditions with influence of temperature (25 °C and 28 °C), aggressiveness of isolates (four isolates from Race 1), and behavior of commercial cultivars (three susceptible cultivars and four not susceptible). In our study, all susceptible cultivars died at both temperatures for all the isolates, while the temperature of 25 °C was lethal for only one plant of a non-susceptible cultivar. The plants of non-susceptible cultivars that did not die presented index symptoms within a range from 1.7 to 3.7 according to cultivars and isolates; however, at 28 °C, all plants of the non-susceptible cultivars were infected, with 30 % to 100 % of plants dead.The results suggest that temperature affects the disease and that, in highly contaminated areas where the lettuce crop is grown in hot periods, management of the disease requires strategies complementary to using non-susceptible or resistant cultivars.