Onion Genetic Resources and Pest Resistance: The Indian Scenario

Onion (Allium cepa) is known to be vulnerable to the attack of several biotic stresses, with yield losses varying from 10–15% annually. Among them, Stemphylium blight (Stemphylium vesicarium) and purple blotch (Alternaria porri) diseases and onion thrips (Thrips tabaci) were identified as of very significant to onion growing world including India. Utilization of resistant sources in the breeding programmes is the most feasible way of combating these pests. The National Bureau of Plant Genetic Resources (NBPGR) is in the forefront of diversity collection in Allium species and subjecting it to characterization and evaluation against biotic and abiotic stresses to support the ongoing crop improvement programmes in India. NBPGR in the Indian context facilitated the import of 1316 accessions of 47 Allium species from 15 countries over the past two decades. The present article strives to illustrate the current status of onion germplasm exchange in the country. The article also elucidates globally available germplasm stocks while distinctly pointing out the sources of resistance to the significant insect pests and diseases and suggests the way forward to enhance the genetic potential of onion varieties through resistance breeding. The need for introducing Allium ampeloprasum, A. bouddhae, A. obliquum, A. nutans and A. odorum possessing traits of resistance to different pests is highlighted. An attempt has been made to discuss on the possibility of utilization of wild species such as A. roylei, A. fistulosum and A. altaicum, which are reservoirs of useful genes.