Functional Adaptation in Heterodera Avenae in Relation to its Survival in the North Indian Conditions

Experiments conducted in vitro in order to understand the adaptation of the cereal cyst nematode, Heterodera avenae, under the natural environment of North India, revealed that presence of moisture and low temperature were the two decisive parameters for hatching of encysted eggs. Dormancy is considered as a functional adaptation induced primarily by high temperatures. It could be broken if newly formed cysts are exposed to low temperature with suitable moisture. Results obtained under laboratory conditions were correlated to the happening of natural phenomenon in the field conditions, where the newly formed cysts, exposed to soil temperatures ranging from 35° — 45°C for atleast five months after the crop harvest in April, would remain viable and infect the crop sown during October or November.