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The glycoalkaloids solanine, chaconine, leptine I, leptine II, solasonine, solamargine, and tomatine, synthesized in the foliage of variousSolanum species, were tested in synthetic diets for their effects on potato leafhopper adults,Empoasca fabae (Harris), at concentrations of 0.03%, 0.09%, and 0.27%. Percent mortality was recorded after a 72 hr feeding period. At the lowest concentration (0.03%), tomatine in the diet resulted in the highest adult mortality (95%) with mortalities ranging from 10% to 41% in the other glycoalkaloid diets. At the highest concentration (0.27%) mortalities ranged from 69% to 100% with no significant (P>.05) differences among the diets. Mortality varied the most among the glycoalkaloid diets at the 0.09% concentration. Chaconine, ubiquitously found with solanine inSolanum tuberosum L., caused significantly (P≤.05) higher mortality (59%) than did solanine (8%). Mortalities with solasonine and solamargine in the diets (55% and 54%, respectively) were not significantly (P>.05) different from the mortality with chaconine in the diet. Including leptines I and II in diets resulted in lower mortalities (28% and 30%, respectively). Mortality was significantly (P≤.05) the highest (97%) with tomatine in the diet.

Glycoalkaloids are important potato quality factors. Tuber-bearingSolanum species exhibit wide quantitative and qualitative diversity in glycoalkaloid contents. Some species, of interest to breeders, contain extremely high total glycoalkaloid (TGA) levels and/or unusual types of glycoalkaloids of ill-defined or unknown toxic and teratogenic properties. Characterisation of glycoalkaloid content is a dynamic and, in some cases, controversial subject. Problems associated with analytical methodology and, to a lesser extent, with environmental effects and intraspecific heterogeneity have probably been the major causes of disagreements in the literature. Recent methodological developments have facilitated more accurate and sensitive measurements of TGA levels and of individual glycoalkaloid compositions. Such measurements should be used to analyze parental material and selected hybrid progeny in breeding programs. This is particularly important when certain wildSolanum species are being exploited as undesirable levels and types of glycoalkaloid can be genetically transmitted from the wild species to hybrid progeny. Absence of glycoalkaloid assessment from a breeding program can result in wasted effort, time and money.

A widely employed, comprehensive method exists for the determination of tuber total glycoalkaloids (TTGA). This method, which consists of a bisolvent extraction, preparation, and purification of aglycones and subsequent titration, was not acceptable for quantification of leaf total glycoalkaloids (LTGA). A modification of an existing extraction procedure was developed and tested. When the original bisolvent and the newly developed acetic acid extractions were contrasted percent recovery of a-solanine from leaf tissue was 19–27% and 91–97%, respectively. This new procedure was easily adapted for TTGA analysis and demonstrated improved recovery of α-solanine from tuber tissue when compared with the bisolvent extraction.

Seven solanaceous glycoalkaloids (α-chaconine, β2-chaconine, α-solanine, dehydrocommersonine, commersonine, demissine and tomatine) and three alkaloids (solanidine, tomatidine and demissidine) were tested for their ability to inhibit acetyl cholinesterase in anin vitro system. Glycoalkaloids at concentrations of 33–41 parts per million (ppm) gave cholinesterase inhibition ranging from 4.2 to 26.8%. All three alkaloids had lower anticholinesterase (4.2 to 15.4%) than the seven glycoalkaloids, except for tomatine. Two well-known cholinesterase inhibitors, carbaryl, a carbamate insecticide and Guthion, an organophosphate insecticide, were also tested for comparison. It required only 1 to 2 ppm of the insecticides to give the same average percent inhibition as was observed with the glycoalkaloids at concentrations of 33–35 ppm.

Tuber tissues of 123 commercial cultivars were tested for their ability to synthesize solamarine glycoalkaloids. Eleven cultivars including ‘Kennebec’ and ‘White Rose’ synthesized major concentrations of solamarines, ranging between 42 and 85% of total glycoalkaloid, when tuber slices were exposed to light during wound-healing. Tuber tissues of the other 112 cultivars did not synthesize solamarines, or they synthesized only trace concentrations of these unusual glycoalkaloids. Nine of the 11 solamarine-synthesizing cultivars have a common ancestor, USDA 96-56. This parental clone synthesizes major solamarine concentrations and it also carries the R1 gene for late blight resistance that it inherited fromSolatium demissum. Results of solamarine analyses of foliage from 47 USDA 96-56 selfed progeny suggest that this parental clone is the source of a major gene(s) for solamarines present in 9 of the commercial cultivars. However, there appeared to be an alternative source of a gene(s) for solamarines because ‘White Rose’, with onlyS. tuberosum ancestors, also synthesized major solamarine concentrations. There was no association between the R1 gene for late blight resistance and the ability to synthesize solamarines in 31 USDA 96-56 selfed progeny that were analyzed for both characters.

Evaluation of the only available method for comprehensive total glycoalkaloid determination was carried out. The method comprised bisolvent extraction of glycoalkaloids followed by purification and non-aqueous titration of the aglycones released from the glycoalkaloids by acid hydrolysis. Our data show that use of the bisolvent extraction procedure can result in poor and variable recovery of glycoalkaloid standard. The post-extraction part of the analysis yielded high and reproducible recoveries of glycoalkaloid standard.