Physiological and Biochemical Criteria for Breeding for Drought Tolerance in Coconut
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2007-02
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Abstract
The ability of coconut genotypes to withstand drought conditions depends upon various physiological and biochemical factors which impart drought tolerance. Among these, the pattern of soil moisture depletion by the roots and transpirational loss of water through the leaf surface were found to be important. The accumulation of wax on the leaf surface and the stability of the activity of certain enzymes were found to have a bearing on stress tolerance. On the basis of the above criteria, .coconut genotypes were ranked according to the degree of tolerance. The hybrids, WCT x WCT, LO x GB, LO x COD and WCT x COD ; the tails, WCT ( selections) and Andaman Giant proved to be drought tolerant having a relatively high depletion of soil moisture by the roots, low transpirational loss from the leaf surface and the high content of cuticular wax, all desirable traits in the conservation of water by the tissues. The dwarfs, COD, MYD, GB and MOD; the tall cultivar, Laccadive Micro; and the hybrid, COD x WCT were characterized by an imbalance of water relations. Their low soil moisture depletion and higher rate of transpiration resulted in their susceptibility to drought; these genotypes also had low wax deposition. Further evidence was obtained through the determination of enzyme activities of glutamate oxalacetic transaminase (GOT) and acid phosphatase (APH), which showed distinct differences between the tolerant and susceptible genotypes. Thus, the much needed link between cellular processes and external manifestation of stress symptoms in coconut was established. The implications of these findings in the breeding programme for drought tolerance in coconut are discussed.
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In: Abstracts, National Symposium on Coconut Breeding and Management, KAU, Velanikkara, Trichur, 23-26 Nov. 1988 p-16