DIPLOID AND TETRAPLOID SOLANUM-CHACOENSE GENOTYPES THAT SYNTHESIZE LEPTINE GLYCOALKALOIDS AND DETER FEEDING BY COLORADO POTATO BEETLE

A selection (8380-1) from Solanum chacoense Bitter (2n=2x=24) accessio n PI 458310 that synthesizes the leptine glycoalkaloids was compared i n growth chambers with tetraploid (2n=4x=48) genotypes derived from ti ssue culture of 8380-1 leaf explants for plant growth habit, leaf glyc oalkaloid content, and effect on the development of Colorado potato be etle [Leptinotarsa decemlineata (Say)] larvae. The plants of the 4x re generant genotypes were more vigorous with larger, more oval shaped le aflets than 8380-1 plants. The leaf concentrations of leptines and tot al glycoalkaloids were significantly lower (about 34%) in the 4x genot ypes than in 8380-1. The proportion of leptines in the total glycoalka loid content was nearly the same (about 80%) in both ploidy groups. In leaf-disk feeding tests, the development of Colorado potato beetle ne onate larvae was not significantly different for the 2x and 4x genotyp es. Both groups significantly slowed development compared with develop ment on cv. Kennebec leaf disks. The 8380-1 selection and a group of 4 x 8380-1 regenerant genotypes are maintained in the Vegetable Laborato ry, Beltsville Agricultural Research Center,Beltsville, MD 20705 and a re available for distribution.