This book has a focus on Insect host plant resistance in different mustard genotypes against aphid as a sap sucker of plants. It also explores the intricate interactions between mustard plants and their insect pests. It delves into the genetic, biochemical and morphological traits that contribute to insect resistance in various mustard genotypes by integrating classical breeding techniques with modern biotechnological approaches. At the end, it has an aim to provide a comprehensive understanding of how mustard plants can be bred for enhanced resistance against insect pests.