Morphological and molecular analysis of coconut(cocos nucifera l.)
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Date
2008
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Department of Plant Breeding and Genetics, College of Agriculture, Vellayani
Abstract
The research project entitled Morphological and molecular analyses of coconut (Cocos nucifera L) was carried out in the Department of Plant Breeding and Genetics College of Agriculture, Vellayani during the year 2006-2008.
The major objectives of this study include genetic analysis of six coconut cultivars with respect to fourteen morphological characters (vegetative and fruit characters),RAPD analysis of the coconut cultivars with 14 oligonucleotide primers and comparison of the genetic divergence of the six coconut cultivars with respect to morphological and molecular markers
The study was conducted in six popular coconut cultivars, WCT, Komadan, Laccadive Ordinary, Natural Cross Dwarf, Chowghat Green Dwarf and Chowghat Orange Dwarf. Morphological data on fourteen biometrical traits in thirty palms belonging to six genotypes, with five palms for each genotype were subjected to statistical analysis. The analyses revealed that magnitude of variation represented by range; phenotypic coefficient of variation and genotypic coefficient of variation were moderately high for all the characters studied. High heritability coupled with high genetic advance was observed for weight of unhusked nut, weight of husked nut and number of nuts per palm per year. The coconut breeder therefore can make his selection on the basis of phenotypic expression of these characters in the individual palms. Correlation studies revealed that all the characters except plant height had significant positive correlation with yield. Path coefficient analysis revealed that eight out of thirteen characters showed positive direct effect on yield.
Genetic divergence studies using Mahalanobis D2 analysis showed that the dwarf accessions are distinctly divergent from the rest of the accessions. The group constellations developed based on D2 totals showed that the local cultivar WCT and NCD were clustered together and the well preferred cultivar Komadan got clustered along with Laccadive Ordinary, the variety of Lakshadweep released in Kerala as “Chandrakalpa” for its superiority in performance.
Maximum divergence was reported between Komadan and NCD .With regard to the characters chosen for the divergence analysis, it shows the importance of nut characters in assessing the genetic divergence in coconut.
RAPD analysis using the 14 primers produced 107 amplicons within the molecular range of 2 kb to less than 0.5 kb. The primers chosen for the study reveal the advantage of GC-rich primers in bringing about amplification. Among the 14 primers studied, OPE-7 and OPB-05 produced maximum polymorphism of 43 percentage. The percentage of polymorphism produced by the 14 primers ranged from 10-43 with an average of 27 percentage. Among the fourteen primers studied, nine primers could produce unique products.The similarity analysis of the RAPD products show that the accessions are divergent with respect to RAPD markers. Similarity indices showed that the two accessions, COD and CGD are having 98 percentage similarity. Komadan had 89 percentage similarity with NCD and only 77 and 71 percentage similarity with WCT and Laccadive Ordinary. The dendrogram constructed also depicts the clustering of Komadan along with NCD and dwarfs. The least similarity was noted between Laccadive Ordinary and Chowghat Orange Dwarf. These divergent accessions can be used as parents for exploiting maximum heterosis.
Divergent analysis with biometrical traits and RAPD markers slightly differed .In both analyses the dwarfs were clustered together. In the analysis with biometrical traits the divergence was 56 per cent and in the RAPD analysis it had 98 per cent similarity. Morphological markers clustered Komadan and Laccadive Ordinary together and West Coast Tall along with NCD. But in the RAPD analysis, West Coast Tall and Laccadive ordinary clustered together and Komadan clustered with dwarfs and NCD at 80 per cent similarity. Even though, Komadan is accepted as a superior palm its pedigree is controversial. A detailed molecular study can give a clear picture.
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