Inheritance of Resistance to Tomato Spotted Wilt Virus in Lettuce (Lactuca Sativa L.)

Abstract

Tomato Spotted Wilt Virus (TSWV), a thrips transmitted virus disease with a wide host range, has become a major limiting factor in lettuce production in Hawaii. Symptoms of this disease on lettuce are necrotic spotting of young leaves, stunting, wilting, and death of the plant. The large host range of this disease has made it difficult to control. Genetic resistance might work, but there have been no reports of resistance in lettuce. Hartmann (personal communication) undertook a preliminary screening program for TSWV resistance and found six lines of lettuce 'Tinto', PI 167128, PI 342510, PI 342517, PI 342522, and PI 342526 that showed less infection with TSWV than the susceptible 'Manoa'. In this study the six lines that Hartmann found plus one more 'Batavia' were tested for TSWV resistance. Only two lines, 'Tinto' and PI 342517 showed significantly higher resistance than the susceptible 'Manoa'. These two resistant lines were crossed with 'Manoa' and each other to produce F1 and F2 seed. Results of testing the F1 and F2 plants suggest that 'Tinto' and PI 342517 have the same genes for resistance and that this resistance is controlled by a dominant or partially dominant gene complex.