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Title: PERFORMANCE OF COLORADO POTATO BEETLE LARVAE (LEPTINOTARSA DECEMLINEATA (SAY) REARED ON SYNTHETIC DIETS SUPPLEMENTED WITH SOLANUM GLYCOALKALOIDS

Author
item KOWALSKI, STANLEY - FORMERLY OF VEGETABLE LAB
item Domek, John
item Deahl, Kenneth
item Sanford, Lind

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Colorado potato beetle is a major insect pest of potatoes in nearly all production areas of the U.S. Controlling this pest with insecticides is expensive and can be environmentally damaging. Development of resistant potato varieties would help alleviate these problems. Chemicals called leptine glycoalkaloids are found in the leaves of the wild potato species S. chacoense. From whole plant studies the leptines have been shown to deter feeding by the beetle. However, other glycoalkaloid compounds are also present and may have affected the results. Experiments were performed that tested the leptine glycoalkaloids for their effects on beetle feeding when added to an artificial diet that contained no plant constituent compounds. Leptine adversely affected beetle feeding with the effect increasing as the leptine concentration in the diet was increased. The results indicate that leptine glycoalkaloids alone do deter beetle feeding and that they can be used in the development of resistant potato varieties. Potato producers will benefit from using such varieties in reduced production costs, and consumers will benefit from lower food costs and lower environmental impacts of insecticides.

Technical Abstract: Glycoalkaloids (GAs) are a class of secondary compounds, ubiquitously distributed throughout the Solanaceae. Numerous studies have shown that certain GAs, e.g., a-tomatine, solanocardenine, and leptine, have a negative impact on performance of the Colorado potato beetle (CPB). The presence of other secondary compounds, as well as the nutritional status of the plants used, are additional variables in such experiments. By rearing CPB, from egg to prepupal stage, on a synthetic diet supplemented with the GAs a-tomatine, a-chaconine, a-solanine, leptine I and the steroidal aglycone solanidine, we have been able to further establish the effects of these compounds on the CPB. Leptine I displayed a dose-dependent negative activity against the CPB when assayed at 0.31, 0.62 and 1.23 mM concentrations; however, by the fourth stadium no effect was found. When CPB were fed a higher concentration of leptine I (2.4 mM), there was a sustained effect in all stadia. At 2.4 mM, leptine I displayed a greater negative impact on CPB growth and development than did a-tomatine. The steroidal aglycone solanidine (2.4 mM) had a significant negative impact on CPB performance. Results are discussed in the context of host plant resistance and insect-plant interactions.