Submitted to: Archives of Phytopathology and Plant Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2006
Publication Date: 1/1/2007
Citation: Kirui, K.G., Misra, A.K., Olanya, O.M., El-Bedewy, R., Ewell, P.T., Friedman, M. 2007. Glycoalkaloid content of some superior potato (solanum tuberosum l.) clones and commercial varieties. Archives of Phytopathology and Plant Protection. 2007 on line. p. 1-11. 2009 42:453-463. Interpretive Summary: Glycoalkaloids are important secondary metabolites in potato tubers because of their toxicity to humans and animals. There is limited published data on the glycoalkaloid content of tropically adapted commercial potato varieties currently grown in Kenya. This research was conducted in order to characterize and quantify a chaconine, a solanine and total glycoalkoloids in commercial potato varieties and clones and evaluate if glycoalkaloid levels are related to late blight resistance in tubers. By using HPLC analysis and bromophenol titration methods, the concentrations of glycoalkaloid were quantified in tuber samples. The concentrations of a chaconine and a solanine ranged from 1.62 to 6.41 mg/100g of fresh tuber weight. No pattern in glycoalkaloid content and variety resistance or susceptibility to late blight was detected however, variation in the content of glycoalkaloid was noted. Both assays resulted in efficient detection of glycoalkaloids with similar results. These findings suggest that the glycoalkaloid content of varieties and clones in Kenya are within safety limits of 20 mg/100g Fwt, however, systematic evaluation of clones using any of the two assay procedures is essential for consumer protection prior to variety registration.
Technical Abstract: Glycoalkaloids are important metabolites in potato because of their toxic properties and harmful effects to humans. This research was conducted to characterize and quantify a chaconine, a solanine and total glycoalkaloids of potato varieties and clones. Glycoalkaloid content in freeze-dried tubers of 15 varieties and clones were determined by HPLC analysis and comparative studies were done with bromophenol blue titration assay for total glycoalkaloids. The elution patterns of compounds were consistent in the two assays. Solanidine, a chaconine and a solanine were present in significant quantities in some genotypes and concentrations of a chaconine and a solanine in varieties ranged from 1.62 to 4.46 and 2.24 to 6.41mg/100g fresh tuber weight (Fwt), respectively. On potato clones, a chaconine and a solanine concentrations ranged from 2.24 to 6.41 and 2.27 to 3.80 mg/100g Fwt, respectively. The lowest and highest total glycoalkaloid content values were recorded on Dutch Robyjn (3.50 mg/100g Fwt), an old variety and Tigoni (15.97 mg/100g Fwt), a late blight resistant variety. There was no consistent pattern in glycoalkaloid content and variety resistance to late blight however, a cultivar dependent variation in alkaloid amount was noted. These results suggest that glycoalkaloid contents of tropically adapted varieties and clones are within the safety limit of 20 mg/100g Fwt. Consistent analysis of glycoalkaloid content prior to variety registration is essential for consumer safety.