Breeding for Aphid Resistance in Rapeseed Mustard

The productivity of oilseed brassicas is severely affected by aphid pests. Among the different aphid species, turnip/mustard aphid, Lipaphis erysimi (Kaltenbach), is the key pest of oilseed brassicas in Indian subcontinent inflicting 35.4–91.3% losses under different agroclimatic conditions. The development of an aphid-resistant cultivar offers an effective, economic and eco-friendly method of its management which requires the availability of a crossable source of resistance. Brassica plants employ a plethora of biophysical and biochemical defence mechanisms against insects, which range from surface waxes and trichomes to production of toxic biochemicals such as glucosinolates, isothiocyanates, lectins, volatiles, alkaloids, etc. Such resistant plants can be identified by an effective screening protocol, and the gene(s) of interest can be transferred to the desirable agronomic background by conventional breeding or marker-assisted selection. Not much progress has been made in breeding for resistance in brassicas against aphids primarily due to non-availability of resistant source within the crossable germplasm as well as lack of knowledge on its trait genetics. Though some success has been achieved to introgress the gene of interest to a desirable agronomic background, it has complex and elaborate breeding requirements. An alternate strategy to conventional breeding is the use of insect-resistant transgenes through genetic engineering, but this strategy has its own associated issues. Thus, the development of aphid-resistant cultivars requires more research on aphid-plant interactions to identify either an effective aphid resistance gene or a phenomenon that can lead to a new mechanism of resistance.