most varieties of apples grown in India are susceptible to apple scab, a fungal disease. The disease is controlled using fungicides but horticulturists are trying to reduce their use and develop apple scab-resistant varieties instead.
Apples originated in Central Asia; so did the fungus Venturia inaequalis which causes the disease. However, very little is known about the fungal isolates in Asia. A recent study carried out by researchers from China, India and the uk throws some light on the subject. "The idea was to understand genetic similarities/differences in fungal isolates in different countries," says Vijay Thakur, who is with the department of mycology and plant pathology, Dr Y S Parmar University, Shimla.
Thakur and other researchers picked up 80 isolates: 20 from the uk, 30 from China and 30 from India. The researchers came up with two findings: one, the isolates were different in different countries, and two, local apple varieties were resistant to local fungal isolates; foreign isolates could cause diseases in local varieties. Most of the resistant genes have originated from small-fruited Asiatic apple species. Hence, these should be used to develop resistant varieties in Central Asia, the authors said in the paper published in the Plant Disease (Vol 92, No 2).
The results assume importance because several of the apple varieties are imported. In India, for instance, resistant varieties are not being developed and planting materials are imported from countries such as the us and the Netherlands.
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