Genetic aspects of tolerance to freezing and ice-cover in gramineous plants
|Larsen Arild||Rannsˇknastofnun landb˙naarins, B˙naarfÚlag ═slands, BŠndaskˇlinn ß Hvanneyri, Rannsˇknast÷ SkˇgrŠktar rÝkisins, Tilraunast÷ hßskˇlans Ý meinafrŠi, Veiimßlastofnun||1989||ReykjavÝk|
Frß vefstjˇra: Greinina Ý heild sinni er a finna Ý pdf-skjalinu hÚr a ofan
In winter cereals, freezing tolerance is controlled both by dominant and recessive genes, both additive and non-additive in wheat, but mostly additive in barley and oat. The heritability for freezing tolerance in winter cereals and grasses is quite high. The hardy cultivars of winter wheat may already possess all the major genes available for freezing tolerance, but in grasses there is still great variation in tolerance to be used in breeding. The genetic background for ice-cover tolerance has not been studied in detail, but the variability should give possibilities for breeding.
Key words: freezing tolerance, genetic aspects, grasses, ice encasement, winter cereals.
ErfafrŠi frost■ols og svell■ols Ý gr÷sum og vetrarkorni
Frost■oli Ý vetrarkorni er stjˇrna bŠi me rÝkjandi og vÝkjandi erfavÝsum, bŠi samleggjandi og ekki samleggjandi Ý hveiti og aallega samleggjandi Ý byggi og h÷frum. Arfgengi frost■ols er fremur hßtt Ý vetrarkorni og gr÷sum. Frost■olin afbrigi af vetrarkorni hafa lÝklega n˙ ■egar alla megin erfavÝsa fyrir frost■oli, en Ý gr÷sum er enn ˇnotaur allmikill erfabreytileiki. Erfagrunnur svell■ols hefur enn ekki veri rannsakaur, en breytileikinn gefur vonir um ßrangur Ý kynbˇtum.
Freezing tolerance and ice-cover tolerance are physical components of the winter hardiness complex of overwintering plants. Winter hardiness was early on shown by field studies to be controlled by many genes like other quantitative characters, as concluded by Nilson-Ehle as early as 1913. Freezing tolerance, which has been recognized as the primary component of winter hardiness, is also a complicated quantitative character, when tested under controlled climatic conditions (Gullord et al., 1975). The same is certainly true for ice-cover tolerance (McKersie and Hunt, 1987) even though this has not been studied to the same degree.
The earliest experiments in this field were aimed at distinguishing between the degree of tolerance of the varieties and genotypes of breeding material. However, to set up a scientifically-based breeding program, the inheritance of the characters involved have to be explained.
Because of their economical importance the winter cereals have been the most, extensively studied. Considerable research attention has been paid to freezing tolerance in winter wheat in particular. Even so, Brule-Babel and Fowler (1987) recently stated that poor understanding of inheritance was a possible reason for lack of progress in breeding for better cold hardiness in winter wheat.