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In order to study the fate of gossypol and tannin when fed to Heliothis virescens larvae, four concentrations of gossypol and tannin (0, 0.02, 0.06 and 0.2%) were incorporated separately into larval diets. Newly hatched 1st instar tobacco budworm larvae were placed on these diets and allowed to feed for 9 days. Each day, samples of larvae were removed from the diets. A total of 225 larvae per concentration was analyzed for the presence of gossypol and tannin. In a second test, larvae were reared on a normal diet for 6, 7, and 8 days. At the end of day 6, 0.2% gossypol and tannin diets were prepared. The 6 day old larvae were removed from the normal diet and placed on the test diets. On day 7, the same lets were prepared and the 7 day old larvae were removed from the normal diet and placed on the test diets. The same procedure was used on day S. The test was terminated after day 9, thus the larvae fed 1, 2, and 3 days on the test diets. Ten larvae were used for each replication. The gossypol test was replicated 5 times (50 larvae) and the tannin test 3 times (30 larvae). After the tests were terminated, we removed the digestive tract (gut), extracted the haemolymph (blood) with a micropipet, and collected the feces. Gossypol and tannin analyses were made to determine the percent recovery (mg of gossypol or tannin per gram of sample). The percent recovery of gossypol and tannin from whole larvae fed on the control (O%) or on any of the three concentrations in the first test was zero. The percent recovery of gossypol and tannin from the gut, blood, and feces after the larvae had fed for 1, 2, and 3 days on a 0.2% diet of the two compounds in the second test was also zero. We concluded from these studies that the tobacco budworm is able to metabolize both gossypol and tannin after ingestion. |
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©National Cotton Council, Memphis TN |
Document last modified Sunday, Dec 6 1998
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