Two years study was carried out during 2006-07 and 2007-08 crop seasons to study the response of different genotypes of oilseeds Brassica to Lipaphis erysimi (Kaltenbach) infestation both under field and screen house conditions and to find out the relationship of various biochemical constituents to aphid infestation. Among the various genotypes, the population of L. erysimi was significantly high on Brassica rapa variety brown sarson cv. BSH 1 and B. rapa var. yellow sarson cv. YST 151 in unprotected set i.e. 53.7 and 52.3 aphids/ plant, respectively. However, it was the lowest on Eruca sativa cv. T 27 (4.7 aphids/plant) followed by B. carinata cv. DLSC 2 (20.9 aphids/ plant) which suffered the least yield loss i.e. 5.79 and 10.59 per cent, respectively. Almost similar trend was observed in seedling mortality, which was the maximum in BSH 1 and YST 151, while no seedling mortality was observed in the case of T 27 during both the years of study. Analysis of various biochemical constituents revealed that glucosinolates, total phenols and ortho-dihydroxy phenols had inverse relationship with the aphid infestation. Higher amount of these biochemical constituents in T 27 and DLSC 2 was responsible for lower aphid infestation on these genotypes.
