ISHS Acta Horticulturae 531: II ISHS Conference on Fruit Production in the Tropics and Subtropics
FATTY ACID COMPOSITION OF ZYGOTIC EMBRYOS OF COCONUT DURING GERMINATION IN VITRO AND EX-VITRO |
| Authors: | A. Lopez-Villalobos, R.K.W. Hornung, Peter F. Dodds |
| Keywords: | micropropagation, callus, somatic embryos, haustorial tissue |
| Abstract:
Although there has been progress in the production of callus for coconut micropropagation, the reliable formation of somatic embryos and the subsequent regeneration of plants await further improvements. The need for a marker, to enhance the screening of culture conditions and media components, and optimise the formation and germination of somatic embryos is paramount in coconut research. The aim of this study was to compare the changes in fatty acid composition in coconut zygotic embryos during germination ex vitro and in vitro in order to assess individual fatty acids as potential biochemical markers for successful germination. Fatty acids were analysed as butyl esters prepared from lipid extracts of mature zygotic embryos germinated in vitro or ex vitro. Embryos were dissected into plumule, coleoptile, haustorium and radicle (hereafter referred to as “embryonic tissue”) in order to achieve a detailed analysis. In addition, liquid endosperm (coconut water) and solid endosperm (meat) from the mature nuts were analysed. Results were expressed as mole percentages and as the mass of fatty acids per gram of tissue or tissue unit. The results showed quantitative differences in fatty acid composition depending on the type of embryonic tissue and on the conditions of culture. Embryonic tissues derived from ex vitro conditions were shown to contain a high percentage and high absolute amounts of the fatty acids 16:0, 18:2 and 12:0. Similarly, 16:0 and 18:2 were high in embryonic tissues obtained in vitro but 12:0 was substantially lower. Unlike other embryonic tissues, haustorium cultured ex vitro was characterised as having both a high percentage and high absolute amounts of 12:0. In contrast, haustorial tissue derived from embryos germinated in vitro did not grow and contained low absolute amounts of 12:0. The accumulation of 12:0 in tissues from zygotic embryo germinated ex vitro suggested that this fatty acid would be a suitable biochemical marker for germination in coconut. Research to characterise fully the “normal” developmental pattern in coconut zygotic embryos, germinated in vitro, is continuing. | |
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