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Morphological Diversity, Genetic Erosion and Indicators of in Situ Conservation of Coconut (Cocos nucifera L.) in Vietnam
Thesis Abstract:
Diversity of coconut is a primary field of study for the purpose of conservation and use germplasm. This study consisted of two main parts: (1) a morphological diversity study in two agroecological zones (the southern part of Central Coastal Line and the Mekong Delta) of Vietnam, and (2) determination of the extent and indicators of genetic erosion and in situ conservation of coconut in the Mekong Delta.
The level of morphological diversity of ‘Green Ta’ tall coconut population was low (in qualitative characters) to moderate (in quantitative characters). Between the zones, the diversity was low; while within the zone, more diversity was observed. The diversity that existed among the zones was due to the diverse environmental condition, especially soil types, regardless of location. There existed two distinct clusters of populations. The big cluster included all population of suitable soils (grey, sandy, and alluvial soils). The small cluster accounted for populations of problem soils (saline and acid sulfate soils). More diversity in terms of morphology was found in coconut planted in suitable soils than in marginal soils.
A total of 120 respondents in three typical zones of the Mekong Delta were related in the study of genetic erosion and conservation of coconut in the farmer field. Coconut genetic erosion measured as decrease in coconut area in this study was not so serious (around 20% for the whole country). It occurred on both problem soils and fertile soil where there existed multiple choices of cash crops (such as mandarin orange, lemon) and high income farming systems (fish and shrimp). Low output of coconut was the main reason for coconut area reduction in all soil types. In alluvial soils, cash crop replacement was the main reason for reduction in coconut area while in saline soils, the land used for aquaculture. Decrease in coconut area occurred least in the acid sulfate soil, where coconut can adapt although with a reduction in yield. Furthermore, other crops could not survive in this kind of soil.
A moderate level of diversity existed in the farms surveyed. Economic factors had the greatest contribution to the diversity of coconut varieties on farm, followed by environmental factors. Cultural factors and government policies did not strongly affect the farmers’ decision in conserving coconut. Farmers selected varieties, which gave them income, thus, inadvertently maintaining varieties which carry precious genes.
