JUST when India thought it would be able to get a big chunk of the global walnut market and began planning towards it, a rare fungus started playing spoilsport. Plant pathologists have isolated the fungus from walnut nurseries in the country for the first time. So far Italy and Argentina have reported sporadic occurrences of the infection in walnut nurseries in 1999 and 2004, respectively. Little research has been done on how to combat the fungus, which kills seedlings within a month of infection. Unless India acts fast, analysts say, it might hit the country’s burgeoning walnut industry. With a 50 per cent rise in production over the previous year, India is all set to be one of the world’s top 10 walnut exporters in the next few years from being the 12th largest exporter.
The infection came to light in September 2008 when scientists at Sher-e-Kashmir University of Agricultural Sciences in Jammu and Kashmir came to know that 60 per cent of the walnut seedlings at the institute’s horticulture station were dying. The scientists tested new walnut varieties at the nursery in Bhaderwah valley. The seedlings had cankers, or dried dead tissue, on the stems. The disease was prominent in two varieties—SKU 0002 and Opex Dachaubaria. “They are said to be disease-free and high-yielding,” says Brajeshwar Singh, plant pathologist at the horticulture station. However, he refused to divulge the origin of the varieties. Investigations showed the canker was caused by soil-borne fungus Fusarium incarnatum. The fungus clogs the food supplying vessels, killing the seedling, says Singh. Though the infection was found in one- to two-year-old seedlings, Singh says it can affect older trees if left unattended. The finding is to be published in Plant Diseases.
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