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Screening of coconut (Cocos nusifera L.) for drought tolerance
By Dewwanthi Karunarathna | February 13, 2008
Drought causes a substantial reduction in national yield of coconut and also a loss of coconut palms in severe droughts thus resulting in serious economic consequences in the coconut industry in Sri Lanka. Therefore, it is a prime importance to identify some putative drought tolerant genotypes for the use in drought prone areas. The long generation and maturation periods of coconut restrict the selection of genotypes based on yield. Therefore, in this study the effects of drought on stomatal conductance (gs) and water potential (Ø) of four coconut genotypes (the accession Clovis [CL] is believed to be tolerant to drought while the rest Dwarf Green [DG], Dwarf Brown [DB] and Cameron Red Dwarf [CRD] are sensitive) were measured to develop an index for stomatal performances (ISP) using ISP = åtx=1 X. FX equation. Where, t, X and F are the number of genotypes, grade point obtained by the genotype for recordings of gs and Ø during drought and frequency of the corresponding grade point respectively. All palms were about 15 years of age and managed according to the recommended practices, in adjacent plots at the Potthkkulama Research Station, in IL1 Agro-Ecological Region. Eight adjacent palms from each of four genotypes were selected. Palms were monitored throughout the 80-day natural drought experienced in early 2005. DB showed the highest ISP (24) while DG (22.5) and CL (21.5) were next with minor differences and CRD (19), being the lowest of all. Thus, CRD can be identified as a drought sensitive genotype compared to the rest. Therefore, four genotypes can be ranked according to drought tolerance in terms of ISP as DB>DG>CL>CRD. However, these results are substantially different from known conditions at the field level. Therefore, more careful observations on much harsher and prolonged drought are needed to verify the applicability of this method.
W G D Lakmini1, N P A D Nainanayake2 and W A J M De Costa3
1Department of Crop Science, University of Ruhuna, Sri Lanka
2Plant Physiology Division, Coconut Research Institute of Sri Lank
Topics: symposium 2006 |