Genetic Study of the Banded Cucumber Beetle Resistance in Romaine Lettuce Cultivar Valmaine

The romaine lettuce cultivar Valmaine has resistance to banded cucumber beetle (Diabrotica balteata ), serpentine leafminer (Liriomyza trifolii), Trichoplusia ni, and Spodoptera exigua, which makes it a highly valuable germplasm for development of new resistant cultivars and for genetic studies of the multi-insect resistance. A lettuce population was developed for analysis of inheritance of the banded cucumber beetle resistance by crossing  ‘Valmaine’ with ‘Okeechobee’. The F₁ progeny performed similarly as 'Valmaine' in response to foliar feeding of the beetle. Of 97 F₂ plants evaluated for response to foliar feeding of beetles, 69 were resistant and 28 were susceptible. The chi-square (χ²) test for the 3 resistance : 1 susceptibility ratio was 0.77 with a P value of 0.38. In partial F₃ families segregating for the beetle resistance, a total of 90 plants exhibited resistance and a total of 23 plants were susceptible. The chi-square (χ²) test for the 3 resistance : 1 susceptibility ratio was 1.30 (P = 0.25). The results indicate that a single dominant gene is responsible for the banded cucumber beetle resistance in 'Valmaine'.  Due to the nature of single gene inheritance, this banded cucumber beetle resistance should be readily transferable into adapted cultivars. A genetic mapping study is underway to identify molecular markers for use in marker-assisted selection.