Variation in damage-yield relations arising out of Globodera species infestation on potato*

The demage-yield relations caused by varying Pis of two separate Globodera species were studied using a susceptible and a resistant potato cultivars. The comparison was on the proportionate yield-basis at two locations under the Southern hills conditions of India.

The study indicated that the external symptoms of damage to plants and the influence of density-dependent factors were evident only in susceptible clone. G. pallida damaged potato more than G. rostochiensis. The host resistance proportionately reduced the nematode damage and using a damage model it was explained. The tolerance values of the two nematode species were found to change according to host sensitivity and location. G. pallida had low values of tolerance while G. rostochiensis had higher values of tolerance.