Screening of Commercial Lettuce Cultivars for Resistance to Fusarium Wilt

Abstract

Fusarium wilt of lettuce is one of the most serious fungal diseases affecting lettuce worldwide. It is caused by a soil-borne fungus, Fusarium oxysporum f. sp. lactucae (FOL), which is found in most areas where lettuce is produced. In this study, 56 commercial lettuce cultivars were tested against three different strains of FOL Race 1 collected from infected fields in Yuma, Arizona: BMP3769, BMP3958, and BMP3932, to quantify resistance and susceptibility. Three-week-old lettuce seedlings were inoculated with an FOL spore suspension during transplantation in greenhouse trials. Each plant was monitored for disease expression and scored using an ordinal wilt scale from 1-6. Plant height data was also collected during the trial period. Several lettuce cultivars were identified as resistant to Fusarium wilt, while others exhibited severe disease incidence or diminished growth due to Fusarium infection. Some cultivars also exhibited differential susceptibility among Fusarium strains and varied susceptibility between repeated trials. Of 32 crisphead cultivars tested, Meridian, Powerball GCHD Progreen Oxy E, and Fredonia were found to be resistant to all three FOL isolates. Only one romaine cultivar, Bondi, of the 16 romaine varieties tested was determined to be susceptible to FOL.