author(s)
BK Sreedhar, TK Hath, SK Sahoo, Debanjan Chakraborthy and Supriya Okram

abstract
Oil seed crops plays a significant role in indian agriculture and industrial economy. Among these Indian mustard (Brassica juncea L.) has a vital role in terms of oil production and with other multiple benefits. Despite beneficial role, Brassica juncea is vulnerable to many insect pests attack especially to mustard aphid. To combat this problem host plant resistance i.e. growing resistant or tolerant varieties is the simple and easiest way to protect the mustard crop from insect pest attack. Varietal screening is done with 51 genotypes of Indian mustard against mustard aphid Lipaphis erysimi to evaluate the resistant or tolerant genotypes on the basis of aphid population density. The experiment was conducted during 2016-17 and 2017-18 in Rabi season at Uttar Banga Krishi Viswavidyalaya, pundibari, Cooch Behar, West Bengal. Categorization of resistant or tolerant genotypes was done on the basis of aphid infestation index (AII) scale, one germplasm was recorded as highly resistant, 20 were recorded as resistant and 30 were recorded as susceptible. None of the genotype recorded as immune and highly susceptible to aphid infestation.