Response of wheat and its relatives to low temperatures

Non-Peer Reviewe

An evaluation of winter hardiness in Saskatchewan forages grasses

Non-Peer ReviewedThe cold hardiness of forage grasses recommended for production in Saskatchewan was evaluated at both the seedling growth stage (fall sown) and from established stands (spring sown). Plant crowns from the established stands were on average approximately 6 °C more cold-hardy than crown tissue of the same varieties at the seedling growth stage. 'Norstar' winter wheat and 'Puma' winter rye were used as standards for cold hardiness comparison. None of the grass varieties which were tested at the seedling stage were more cold hardy than Puma rye. The least cold hardy forage grasses, orchard grass and reed canary grass, were considerably less cold-hardy than Norstar winter wheat. Fall seeding of these species is not recommended because of the high risk of winter-kill. Many other varieties would need adequate snow-cover to ensure winter survival if fall sown. When spring sown, the least cold-hardy varieties were similar in cold hardiness to Norstar. Once established, many other varieties had cold hardiness levels similar to Puma rye

The development of super-hardy winter wheat cultivars: identifying the pieces of the cold hardiness puzzle

Non-Peer ReviewedSeveral years of investigation of the genetics of cold hardiness in wheat, and attempts to improve the cold hardiness of this crop, have identified a number of 'pieces' in the cold hardiness puzzle. The cell cytoplasm does not appear to have any direct effect on cold hardiness, nor on the expression of nuclear genes affecting cold hardiness in wheat or its relatives. Cold hardiness appears to be controlled mainly, although not exclusively, by additive gene action. The most promising source of new genes for the improvement of cold hardiness in wheat appears to be from the rather distantly related wheatgrass group and rye. The chromosome doubled hybrids of rye and crested wheatgrass with wheat exhibited none of the superior cold hardiness found in these donor species. Three explanations were found which help to explain the expression of these alien genes in a wheat background: 1) specific wheat chromosomes were found to affect the expression of rye genes, 2) the species contributing the greatest number of chromosomes in an interspecific cross has the greatest influence on cold hardiness, and 3) increasing the chromosome number, as when the chromosome number is doubled to make an interspecific hybrid fertile (e.g. Triticale), results in an increased cell size which gives the plant less cold tolerance than would be genetically expected. Small cell size was also found to be a factor related to cold hardiness within wheat cultivars. Methods for the improvement of cold hardiness in winter wheat are proposed based on these findings

Quantitative expression of cold-acclimation genes in wheat (Triticum aestivum L.)

Non-Peer ReviewedWinter wheat (Triticum aestivum L.) is seeded in the fall, regrowth resumes in spring, culminating in an early summer harvest. Yield is generally 20-25% higher than spring wheat. However, winter damage/kill can reduce yield. The low fall temperature allows the wheat plant to cold acclimate – a process during which physiological and biochemical changes occur resulting in the plant being able to withstand freezing temperatures. Specific cold regulated (COR) genes, such as Wcs120, are involved in these changes. Expression of COR genes are induced by transcriptional activators, such as WCBF1, in response to low temperature (LT). However, winter damage can still occur due to genetic differences limiting low temperature acclimation. An understanding of this cold acclimation/tolerance process will allow for better breeding strategies to improve winter wheat survival. Thus, the objective of this study was to determine the quantitative expression of some COR genes from field and growth chamber-grown winter and spring wheats using quantitative real-time PCR and establish their correlation, if any, to LT50 values (temperature at which 50% of plants are killed). Winter wheat (Norstar), spring wheat (Manitou) and two near-isogenic lines (Spring Norstar and Winter Manitou derived from reciprocal crosses of the two varieties) were used. Leaves were sampled on three dates (Sept. 29, Oct. 12 and Oct. 26, 2004) for the field grown plants and after 0, 2, 7, 14, 21, 28, 42, 56, 70, 84 and 98 days of LT acclimation for the growth chamber-grown plants. Relative expression of Wcs120 and WCBF1 genes were determined. Initial expression was high for both genes upon exposure to low temperature for all four lines from the growth chamber experiment. Expression decreased upon longer acclimation periods. The winter hardy wheat, Norstar, showed highest relative expression for both genes compared to the three other lines. This research implies that response to LT is very rapid and that accumulated LT tolerance (LT50) and LT tolerance gene translation, as revealed by accumulation of Wcs120, lags considerably