An understanding of the genetic regulation of low-temperature (LT) tolerance is a prerequisite for the development of cold tolerant cultivars for high stress regions. The objectives of this study were to determine if LT tolerance genes are developmentally regulated. Low-temperature response curves were determined for spring wheat and barley genotypes grown at 4°C under 8 hour (h) short day (SD) and 20 h long day (LD) photoperiods for various acclimation periods up to 112 days. Final leaf number (FLN) and growth of shoot apex was used to determine the stage of phenological development. Expression of LT tolerance genes was determined by LT50. A delay in transition from the vegetative to the reproductive phase in SD sensitive, non-hardy AC Minto spring wheat and highly SD sensitive Dicktoo barley grown under SD resulted in an increased level and/or longer retention of expression of LT tolerance genes. In vernalization requiring winter genotypes photoperiod response of SD sensitive winter barley and wheat genotypes was reflected in the level of expression of LT tolerance genes beginning in the early stages of vernalization and plant development. A delay in transition to the vegetative stage allowed LT acclimation to continue to colder temperatures under SD compared to LD conditions in photoperiod sensitive genotypes. To determine the interrelationships between the developmental stages and LT gene expression, winter wheat genotypes were LT acclimated at 4°C under SD and LD from 0 to 112 d. Also, three de-acclimation (20C) and re-acclimation cycles were used beginning before and after vegetative/reproductive transition. Development of the SD de-acclimated plants was greatly delayed compared to LD plants as determined by shoot apex development, and this delay was reflected in the ability of SD plants to re-acclimate to much lower temperatures. Results indicated that expression of LT tolerance genes is governed by developmental regimes and plants in the vegetative phase have a much greater ability to LT acclimate than plants in the reproductive phase. These results support the hypothesis that level and duration of expression of LT tolerance genes determine the degree of LT tolerance and that LT tolerance genes are developmentally regulated.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-10212004-002431 |
| Date | 01 January 2001 |
| Creators | Mahfoozi, Siroos |
| Contributors | Fowler, David |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-10212004-002431 |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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