Isozyme and morphological variation in a Cornus florida L provenance plantation representing geographically diverse populations

Starch gel electrophoresis and principal component (PC) analysis were used to determine the levels of genetic variation and the relationship between morphology and geographic origin for Cornus florida (flowering dogwood) populations in a Michigan provenance plantation. The populations are representative of the species' geographic distribution, ranging from Texas to Georgia and north to Connecticut and Michigan. Allelic variation at 11 loci encoded by 5 enzymes was very low in comparison to other plant species. On average, populations displayed 1.16 alleles per locus, 9.89% of loci polymorphic, with an observed heterozygosity value of 0.048. Genetic identify values ranged from 0.961 to 1.00 and displayed no relationship with geographic origin, While the isozyme analysis revealed little genetic variation, the PC analysis revealed a considerable amount of morphological variation. Most variation (83.3%) in leaf and flower bud morphology was explained by three PCs. Leaf characters revealed no relationship with geographic origin, However, flower bud size and number of florets decreased with changes in latitude from northern, central, and southern populations, respectively, The relationship between flower bud size and latitude suggests an adaptive response to photoperiod throughout the species' geographic range.