Cuticular wax composition in Cocos nucifera L.: physicochemical analysis of wax components and mapping of their QTLs onto the coconut molecular linkage map

Abstract

Cuticular waxes were extracted from the leaves of a coconut mapping population generated by the controlled cross of an East African Tall and a Rennell Island Tall genotype for the construction of molecular linkage maps. The wax composition was analyzed by capillary gas chromatography/mass spectrometry, and for eight of the wax compounds, their absolute and relative amounts were determined. As reported previously for a different coconut ecotype (Malayan Yellow Dwarf), lupeol methyl ether, isoskimmiwallin, and skimmiwallin were identified as the major components of coconut cuticular wax. The additional compounds were characterized as 3-β-methoxy lupane (lupane methyl ether), lupeol and the acetic acid esters of lupeol, skimmiwallinol, and isoskimmiwallinol, respectively. Minor, nonidentified compounds amounted to some 5% of total wax content and included triterpenoids, sterols, primary alcohols, and fatty acids. The variation detected for parents and progeny with respect to the wax components allowed quantitative trait locus (QTL) analyses for their biosynthetic pathways. A total of 46 QTLs could be mapped onto the coconut linkage map which was extended by amplified fragment length polymorphism and single sequence repeat markers into a high density map with more than 1,000 mapped DNA markers. Several colocated QTLs for different traits were detected reflecting the observed correlations among characters.