National Horticultural Research and Development Foundation, Regional Research Station, Salaru, Karnal (Haryana)
National Symposium on “Plant Pathology in the Changing Global Scenario” held at National Bureau of Plant Genetic Resources, New Delhi on February 27–28, 2009
Onion (Allium sativum L.) is a most economically important crop in India. At least 18 other Allium species are consumed as fresh vegetables, pickled, or used as flavoring. However, the onion bulb is the most economically valuable species in Northern part of India. The distinctive flavor or odor of Allium spp. is produced when plant tissues are brushed or cut, and the enzyme allinase hydrogenase S-alkenyl cysteine sulfoxide precursors to form volatile sulpher compounds. Iris Yellow Spot Virus (IYSV), is an emerging disease of onion in the world. The disease as first reported on onion seed crops in the Treasure valley in Idaho in 1993, but has since reported on onion from Australia, Brazil, Chile, India, Isreal, Japan, Reumion Island, Slovenia and Spain. In India, the IYSV reported only in seed crops in some parts of Maharastra earlier, but in Northern parts of India the disease was not reported so far either in bulb crop or seed crops. During 2006–07 and 2007–08 surveys, the field infected onion plants exhibited characteristics symptoms of chlorotic spindle or diamond shaped lesion on the leaves and scapes, with twisting or bending flower bearing stalks, were observed in Haryana, Punjab and other Northern states. In advanced stages, single spindle shaped cholorotic lesion coalesced, leading to withering of leaves, scapes and bulbs are also affected. IYSV is a topsovirus and transmitted through thrips (Thrips tabaci). Effective and long term management of IYSV in onion bulb crops will depend on a multifaceted approach that integrates host resistance, modified cultural practices and judicious use of chemical tools.
