Segregation of leptine glycoalkaloids and resistance to Colorado potato beetle (Leptinotarsa decemlineata (Say)) in F2 Solanum tuberosum (4x) x S-chacoense (4x) potato progenies

Solanum chacoense Bitter is resistant to the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say). Resistance has been associated with the pr esence of a rare class of glycoalkaloids, the leptines. In this study, seve n tetraploid, F2 S. tuberosum x S. chacoense families were evaluated for fo liar production of leptines I and II, leptinines I and II, and alpha-solani ne and alpha-chaconine; and screened for resistance to CPB in the laborator y and field. Resistance was correlated with the concentrations of glycoalka loids on a family and an individual basis. Leptine concentrations ranged fr om undetectable to a high of 18.0 mg/g dry weight. All of the progeny produ ced solanine and chaconine. Family 9623 had the highest mean leptine concen tration and the lowest mean leaf disk feeding and CPB defoliation levels. F amily 9616 had the lowest mean glycoalkaloid concentration and ranked as on e of the most susceptible families. Regression analyses of solanine + chaco nine, leptine I and II, and leptinine I and II foliar concentrations versus leaf disk consumption and field defoliation revealed that only increased f oliar levels of leptines resulted in decreased CPB feeding. The regression models for leptines versus leaf disk consumption and field defoliation were highly significant, accounting for 17% and 26% of the variation in consump tion and defoliation, respectively. To the best of our knowledge, this is t he first work reporting the impact of leptine and leptinine concentrations on CPB feeding in tetraploid, S. tuberosum x S. chacoense potato hybrids. R esults are discussed within the context of breeding for resistance to CPB.