Pre-ingestive and post-ingestive effects of soya bean extracts and rutin on Trichoplusia ni growth

Total ethanolic crude extracts from soya bean (Glycine max L. Merrill) PI 2 27687 and 'Davis', three purified fractions (A, B and C) from PI 227687, an d pure rutin were tested for their effect on the growth of Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae) larvae, from egg hatching to pupation. An alysis of covariance (ANCOVA), followed by bicoordinate utilisation plots, was used to remove the effect of feeding time from consumption and weight o f pupae and to separate pre- ingestive and post- ingestive effects of diffe rent diets on T. ni growth. Survival, pupal weight, and feeding time of T. ni were all negatively affected by PI 227687 total extracts. Pupal weight a nd consumption remained affected by diet, after removing the effect of feed ing time by ANCOVA. Larvae fed on the 'Davis' extract diet grew larger and consumed more rapidly a larger amount of food than those fed on PI 227687 a nd control diets. T. ni pupal weight was strongly influenced by consumption . In general, those insects that consumed more food were heavier but larvae fed on diet containing PI 227687 extract grew less than the others, irresp ective of the amount of ingested and digested food. The feeding time was ad versely affected by PI 227687 fraction A, composed of two flavonol glycosid es (rutin and quercetin 3-O-glucosylgalactoside) and of an isoflavone glyco side (genistin). Survival and pupal weight were not affected, although the consumption and assimilation of ingested food was lower when larvae were fe d on fractions A and C. The toxicity of the higher rutin concentration (2%) was similar to that observed when the insects were fed on unfractioned PI 227687, except that effects on food consumption were not observed. Results indicated that the feeding deterrence of PI 227687 must be caused by other compounds from fractions A and C. Moreover, rutin, acting as an antibiotic, appears to account for the adverse effects of PI 227687 on the physiology of T. ni.