Genetic Studies And Improvement Of Pinus Caribaea Morelet

Pinus caribaea is a tropical pine that is widely planted as an exotic. It is an important plantation species for industrial purposes in China. The objective of this thesis was to collect basic information on genetic variation, breeding system and performance of a range of seed sources which have potential for incorporation into the Chinese breeding programme. Isozyme markers were used to look at genetic diversity, population structure and breeding system of the species. DNA techniques together with isozyme markers were used to distinguish an unknown seed source. Quantitative analysis of morphological traits was also conducted for a field provenance/progeny trial.Isozyme variation was studied in natural populations of two geographically separated varieties, P. caribaea var. caribaea and P. caribaea var. bahamensis, and in exotic populations of the varieties from China and Australia respectively. There was significant genetic differentiation between the two varieties. Within the varieties, populations of var. bahamensis were more differentiated than those of var. caribaea. Exotic populations of both varieties experienced higher inbreeding than natural populations. With var. bahamensis, the Australian population was genetically similar to natural populations. However there were large genetic differences between the Chinese population and the natural populations of both var. caribaea and var. bahamensis. The Chinese material was identified as a distinct species or hybrid by the use of chloroplast DNA variation. Mating systems in natural and seed orchard populations of var. caribaea were analysed using isozyme markers. Both single and multilocus estimates of outcrossing rate were significantly smaller than 1.0 (complete outcrossing) in the island population, but were not significantly less than 1.0 in mainland populations and the seed orchard population, indicating that stronger inbreeding exists in the island population. The small differences between single and multilocus estimates suggest that the inbreeding detected within the variety is caused by true selfing rather than consanguineous mating. The selfing rates ranged from 10.6 % in the island population to 1.5 % in the seed orchard based on 5 loci assayed. Estimates of female outcrossing rates were found to be variable among individual trees though this was probably caused by sampling error.Quantitative analysis of three growth traits, height, diameter and crown width were conducted in a field trial of P. caribaea var. bahamensis located in China. Significant...