genetic variation in the frost hardiness of pinus banksiana lamb. (jack pine) in northwestern ontario
abstract
to estimate the level and pattern of variation in frost hardiness,
artificial freezing tests of 64 provenances of jack pine were conducted.
the provenances originated from northern ontario. seedlings of the
provenances were grown in a uniform environment in a shade house.
current-growth needles were collected in fall during three consecutive
years , 1988 to 1990, and in mid-summer in 1990. three test temperatures
and a control were used for all freezing trials. temperatures ranged from -
19° c to -1° c and duration varied from three to one hours. freezing injury
was evaluated visually. two way anova indicated statistically significant
provenance and provenance x temperature interactions. these results
suggested that the tested jack pine provenances exhibited genetic
variation in their development of frost hardiness and implied a certain risk
in transferring seed from one environment to another. differentiation
among provenances could not be detected during early august 1990.
regression analyses examined the associations between various degrees of
injury and climatic gradients. these analyses suggested that several
selective forces, including precipitation and temperature, were partially
responsible for differentiation among the tested provenances. principal
component analysis (pca) of the data generated three significant principal
components which accounted for approximately 60% of the total variation.
regression of pca scores against climatic gradients also reflected
adaptive variation. however, a number of provenances which originated
from regions with low temperatures and very short frost-free periods
showed no higher levels of frost hardiness than provenances from areas
with longer frost-free periods and higher temperatures. low levels of
consistency were found among the different trials. possible reasons for
the observed inconsistencies were assumed to be i) weaknesses of the
scoring technique, ii) the random effect of supercooling and, iii) the uneven
distribution of temperature in the freezer.
collections
- retrospective theses [1604]