Amplified fragment length polymorphism (AFLP) markers allow a rapid assessment of the level of genetic variation that would be difficult to evaluate using a limited number of morphological markers. AFLP was used to assess the level of genetic variation among 16 different Phalaenopsis species and hybrids. Ten AFLP primer combinations were used for genetic analysis of these Phalaenopsis and 95% of polymorphism in 16 Phalaenopsis species and hybrids was detected. The genetic similarity among Phalaenopsis species and hybrids ranged from 0.298 to 0.774 based on Dice coefficient. The dendrogram derived by UPGMA analysis clustered into two main groups. A significant linear relationship (r² = 0.524, P < 0.0001) was observed between known pedigrees and AFLP-derived genetic similarity for 136 pairwise comparisons of Phalaenopsis species and hybrids. The results indicate that there is an abundance of genetic diversity among within Phalaenopsis and that AFLP can be used to distinguish morphologically similar genotypes. In a second study, the effect of gametophytic selection on genetic diversity in Phalaenopsis was examined by AFLP analysis. Sixteen F1 seedlings resulting from cross-pollination that occurred within high (30 ºC) and low (14 ºC) temperature incubators between two hybrid Phalaenopsis [P. (Taisoco Windian à Sogo Yukidian) by P. hybrid unknown], were subjected to genetic analysis by AFLP. A total of 651 fragments ranging in size from 100 to 350 bp were detected using six primer combinations, of which 387 (59.4%) were polymorphic. Seedlings derived from different temperature treatments exhibited 25.5% to 35.9% polymorphism. The genetic similarity among 16 F1 seedlings ranged from 0.825 to 0.946 based on the Dice coefficient. A dendrogram based on 387 polymorphic markers was derived by UPGMA analysis resulting in three major groups and one subgroup. The dendrogram analysis showed clear clustering in Phalaenopsis hybrids pollinated under different temperature treatments, suggesting that several loci may have been selected during the divergent temperature stress treatments during pollination and early pollen tube growth.

Master of Science