Abstract
Teak leaf skeletonizer, Eutectona machaeralis Walker and defoliator, Hyblaea puera Cramer are the key insect-pests of Tectona grandis L.f. causing severe epidemic defoliation in all teak growing areas. 167 clones of teak belonging to ten states of India, growing at National Teak Germ Plasm Bank, Chandrapur (Maharashtra), were evaluated for natural resistance against these pests. Four-year study showed that ORANR-3 of Orissa and APT-14 of Andhra Pradesh were the most resistant and most susceptible clones respectively. On the basis of visual observations, the remaining clones were categorized according to degree of resistance such as highly resistant (17), resistant (28), moderately resistant (38), least resistant (30), moderately susceptible (32), susceptible (13), highly susceptible (6) and most susceptible (2). Nine clones from each category were selected and seedlings were raised at this Institute from root-shoot cuttings brought from Chandrapur. Damage intensity was measured and the leaves of these clones were subjected to chemical analysis. Foliar Phosphorus, Calcium and Magnesium content were found to be significantly highest in most resistant clone, i.e., ORANR-3 and lowest in most susceptible clone, i.e., APT-14. The amount of chlorophyll a and b was recorded maximum and minimum in APT-14 and ORANR-3 respectively. Results have been discussed in context of the reciprocal interaction between antixenosis resistance in selected teak clones and biochemical parameters in teak leaves.
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