Breeding for Disease and Pest Resistance

Hybridisation and selection have been used to release many crop varieties bred specifically for resistance to fungal, bacterial and viral diseases. Table 9.1 lists examples such as the wheat variety Himgiri, resistant to leaf and stripe rust and hill bunt; the Brassica variety Pusa Swarnim (Kara Rai), resistant to white rust; the cauliflower varieties Pusa Shubhra and Pusa Snowball K-1, resistant to black rot and curl blight; the cowpea variety Pusa Komal, resistant to bacterial blight; and the chilli variety Pusa Sadabahar, resistant to chilli mosaic virus, tobacco mosaic virus and leaf curl. A further example is Parbhani Kranti, a variety of bhindi (Abelmoschus esculentus) given resistance to yellow mosaic virus by transferring the trait from a wild relative species. Resistance to insect pests can arise from morphological, biochemical or physiological features of the plant — hairy leaves, for instance, are associated with resistance to jassids in cotton and the cereal leaf beetle in wheat; solid stems in wheat discourage the stem sawfly; smooth leaves and nectar-less cotton varieties fail to attract bollworms; and maize with high aspartic acid but low nitrogen and sugar content resists maize stem borers. Table 9.2 lists bred examples of pest resistance, including the Brassica (rapeseed- …