Volume 30 Number 1 Article 31 Pages: 28-29
Year 1976 Month 1
Title: Development of Cold Hardy Blueberry Hybrids
Author: C. Stushnoff
Citation
Abstract:
A breeding program was initiated in 1968 with the goal of developing clod hardy, high yielding, high quality, low statured blueberries for production in Minnesota.
We have identified three major components that should be considered in selecting cold hardy blueberry flower buds: 1) The onset and rapidity of cold hardening; 2) minimal survival temperatures; and 3) ability of selections to resist loss of cold tolerance following warm periods from mid-winter to early spring.
Variation for the first criterion exists among various taxa and has been utilized in breeding objectives.
Test winters in 1972 and 1973 provided minimums of -37°C, Dec. 7 and -39°C Jan. 2 without appeciable snow cover illustrating the validity of selecting for ability to resist severe low temperatures.
Freezing test data has also also illustrated that up to 6°C of cold hardiness can be lost following a warming trend in mid-winter (minimums at or near 0°C for 2 weeks). from both natural and artificially induced conditions.
The test winters provided an opportunity
to examine some aspects of
breeding behavior for our seedling
progenies.
Pooled frequency distributions
of 5,414 seedlings, representing
over thirty different parents, for flower
bud survival did not fit normal or
Poisson distributions.
Significance for
skewness may be expected because
the ratings followed record low temperatures
compared to historical lows.
Deviance from expected Poisson occurred
in only a few classes and was
probably due to inability of observers
to realistically evaluate flower bud injury
on a subjective basis for 10
classes.
Otherwise, distribution would
imply continuous variation for adaptation
to the two temperature extremes
measured.
If inheritance is quantitative,
as can only be speculated upon
with this data, we can assume further
improvement is possible by capitalizing
on the genes for cold resistance
in classes 7, 8, and 9 which represent
survivors with little or no injury.
The probability of obtaining hardy
seedlings was calculated for several
parents which were used consistently
as males on several females.
Parents
which were grown and selected in
Minnesota were more likely to produce
hardy seedlings than germplasm
from other locations.
One parent produced
hardy seedlings ten times as
frequently as all others.
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