North American Fruit Explorers mailing list at ibiblio

[Douglas Woodard <dwoodard@becon.org>]

For your information,  a couple of posts from the grapebreeders list.

Doug Woodard
St. Catharines, Ontario, Canada

*****

Probably one of the best conceptual outlines of plant cold hardiness was
published by Stushnoff many years ago*. "Hardiness" is described as
having a number of components, which can vary independently among
different genotypes:  The TIMING of the acquisition of cold hardiness in
the Fall, the RATE at which hardiness is acquired, the ultimate DEGREE
of midwinter cold hardiness, the RESISTANCE TO DEHARDENING in response
to midwinter warm spells, the ability to REGAIN cold hardiness if in
fact dehardening does occurs, the TIMING and RATE of loss of cold
hardiness in the spring.  This helps to explain why a particular
genotype may prove "hardy" in one location and "nonhardy" in another,
even though the midwinter minimums may be similar.  Hope this is clear.

- pp

*Breeding and Selection Methods for Cold Hardiness in Deciduous Fruit
Crops.  Hortscience, 7(1): 10-13.  1972.

*****

No doubt about it - cold hardiness is a very complex trait.

In fact, even at the phenotypic level it is complex; really it is a
collection of traits including acclimation, dormancy, etc.

There are 100's if not 1000's of genes involved here.

That type of trait is called quantitative, as opposed to the Mendalian
dominant-recessive model.  And the genetic loci involved are called
QTL's, for Quantitative Trait Loci.

You have intra & extra-cellular water movement, cryoprotectant
molecules, signaling molecules (ex. abscisic acid (ABA)), etc.

So the basic rule to use in hardy breeding is to use at least one hardy
parent if you want hardy seedlings......................

MH