BIOCHEMICAL-MECHANISMS OF RESISTANCE TO INSECTS IN SOYBEAN - EXTRACTION AND FRACTIONATION OF ANTIFEEDANTS

Leaf extractables/fractions obtained from the leaves of soybean PI 227 687 showed greater antifeedant activity towards the third-instar larva e of the cabbage looper, Trichoplusia ni (Hub.). Extraction of leaves with ethyl acetate followed by 60% methanol, and counter-current parti tioning of leaf extractables between ethyl acetate, water and hexane w as not convenient for isolation of antifeedants. Methanol (60%) in wat er extracted most of the antifeedants from leaves, and this extract wh en partitioned between ethyl acetate and water (the latter repeatedly extracted with the former), concentrated the antifeedants from soybean leaves for further processing on thin layer chromatography or high pe rformance liquid chromatography. There were quantitative differences i n ethyl acetate fraction of PI 227687 (6%) and Davis (3.2%), and in fl avonoids resolved at Rf 0.10-0.20 in benzene: ethyl acetate: methanol (4:3:3). Most of the flavonoids with antifeedant activity resolved at Rf 0.10-0.80. The antifeedant activity of flavonoid bands from PI 2276 87 was greater than the corresponding bands of Davis.