LEPTINES AND OTHER GLYCOALKALOIDS IN TETRAPLOID SOLANUM-TUBEROSUM X SOLANUM-CHACOENSE F-2 HYBRID AND BACKCROSS FAMILIES

The leptine glycoalkaloids from Solanum chacoense Bitter are potential resistance factors to Colorado potato beetle, Leptinotarsa decemlinea ta Say. A selected sample of 17 F-1 hybrids (4x) from crosses of a 4x S. chacoense clone that synthesizes leptines (8380-1) with 4x S. tuber osum L. lines were selfed to generate FZ hybrids (4x) and were also ba ckcrossed to S. tuberosum. Glycoalkaloid (GA) content in foliage and t ubers was measured for 786 sibling genotypes from the two generations in the field at Beltsville, Maryland, Leptines were found in the folia ge of all F-2 hybrids and in 98% of the backcross genotypes. Leptines were not detected in tubers hom either generation. Foliage concentrati ons of leptines for the F-2 hybrids averaged 156 mg/100g fresh weight (FW), The proportion of the total GA content consisting of leptines av eraged 42%. By backcrossing the F-1 hybrids to S. tuberosum the averag e concentration of leptines was reduced to 44 mg/100g FW. The proporti on of leptines averaged 16%. The tuber contents of solanine plus chaco nine glycoalkaloids averaged 52 mg/100g FW for the F-2 hybrids and 27 mg/100g for the backcross genotypes.