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Title: QTL MAPPING OF GLYCOALKALOID AGLYCONES IN SOLANUM TUBEROSUM X S. BERTHAULTII POTATO PROGENIES: QUANTITATIVE VARIATION AND SECONDARY METABOLISM

Author
item YENCHO, G. - NORTH CAROLINA STATE UNIV
item Kowalski, Stanley
item KOBAYASHI, RUTH - PAUL ECKE RANCH
item SINDEN, STEPHEN - FORMERLY VEGETABLE LAB
item BONIERBALE, M. - INTERN. POTATO CTR., PERU
item Deahl, Kenneth

Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Potato breeders frequently use wild species of potatoes as sources of genes for resistance to insect pests. When crosses are made, many genes from the wild species move into the cultivated variety. Some of these genes are beneficial, some harmful. Potato breeders pay particular attention to genes which make chemical compounds known as glycoalkaloids, which most species of potatoes naturally produce. If present in the potato tubers at high concentrations, glycoalkaloids can present a health risk to consumers. However, glycoalkaloids in the leaves can act as insecticidal compounds. In either case, it is important to be able to detect and identify genes for glycoalkaloids. By using a molecular approach (gene mapping), we have located genes for glycoalkaloids on chromosomes 1, 4, 6 and 12. These genes control the production of glycoalkaloids found in both the cultivated potato and also a wild species used in a breeding program. This information is of theoretical interest to biochemists and geneticists, who want to understand how plants make glycoalkaloids. It is also of practical interest to plant breeders, who want to more precisely manipulate these genes, as they develop new and improved varieties of potato.

Technical Abstract: Glycoalkaloids (GAs) are found throughout the genera Solanum (potato) and Lycopersicon (tomato). Certain GAs, i.e., tomatine, solanocardenine, and leptine, have been implicated as resistance factors to the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say). The pesticidal properties of these GAs have primarily been demonstrated by studies in planta, correlating CPB resistance with high levels of foliar GAs: solanocardenine in S. neocardenasii, tomatine in S. pinnatisectum, and leptine in S. chacoense. Although the evidence that these GAs mediate resistance is compelling, controlled analyses of CPB response to purified GAs, fed to insects in synthetic diets, are necessary to characterize the allelochemic nature of these compounds. In this study, CPB reared on a meridic, synthetic diet supplemented with increasing concentrations of tomatine experience retarded growth and delayed development. These effects were evident throughout the insect's development, from egg to prepupal stage. Tomatidine (the aglycone of tomatine) has no effect on CPB, suggesting that the tetrose moiety of the glycoalkaloid is essential for insecticidal activity, consistent with a membrane-lytic mechanism of action.