Candidate Trees Research Articles

A method for molecular phylogeny construction by direct use of nucleotide sequence data

A method for molecular phylogeny construction is newly developed. The method, called the stepwise ancestral sequence method, estimates molecular phylogenetic trees and ancestral sequences simultaneously on the basis of parsimony and sequence homology. For simplicity the emphasis is placed more on parsimony than on sequence homology in the present study, though both are certainly important. Because parsimony alone will sometimes generate plural candidate trees, the method retains not one but five candidates from which one can then single out the final tree taking other criteria into account. The properties and performance of the method are then examined by simulating an evolving gene along a model phylogenetic tree. The estimated trees are found to lie in a narrow range of the parsimony criteria used in the present study. Thus, other criteria such as biological evidence and likelihood are necessary to single out the correct tree among them, with biological evidence taking precedence over any other criterion. The computer simulation also reveals that the method satisfactorily estimates both tree topology and ancestral sequences, at least for the evolutionary model used in the present study.

Phenotypic selection in Betulapapyrifera

Phenotypically superior trees of Betulapapyrifera Marsh, were identified on the basis of their breast height stem diameters in two even-aged stands in western Maine. The growth superiority of each of the candidate trees was evaluated further using one of three different selection methods. Two methods were based on mean annual volume increment and differed in regard to their use of comparison trees. Selected trees were those which grew the most volume throughout the life of the stand. In the third procedure, periodic basal area increment was compared with the estimated basal area increment using an equation incorporating crown surface area as an independent variable. Trees rated as most superior were those which produced the largest increment in relation to crown size. Open-pollinated progenies of selected and control trees were evaluated for height growth and stem diameter in a greenhouse trial. Although significant differences in height existed among the selection methods, no one method was successful in identifying trees whose progenies, as a group, were significantly taller than the average of the control progenies.

Effect of physiological age of stem and IBA treatment on rooting of branch cuttings of Taxus baccata L.

The natural population of Taxus baccata L. (Himalayan Yew) throughout the Indian Himalayan Region is greatly reduced due to its extensive and reckless exploitation for “Taxol” an anticancer drug. The effects of overexploitation are exacerbated by the species poor regeneration process, slow growth rate and prolonged seed dormancy. Therefore vegetative propagation by branch cuttings seems to be only practical solution for its large scale multiplication. A study was conducted on six candidate trees (CTs) to examine the effect genotype, physiological age of stem, IBA treatment on rooting of Taxus baccata cuttings. Results revealed that rooting behaviour of cuttings was significantly affected by all the factors under study. Among the six CTs studied, CT 2 (from BSI, Shillong) had given the highest rooting response (46.28%). The juvenile cuttings have the higher rooting capacity; however the callusing was more prominent in mature cutting. The influence of IBA treatment was also significant for rooting where 1000 was most effective for stimulating rooting juvenile cuttings and 2000 ppm in mature cuttings.