Basic Development Rate in Spring Wheat1
- R. G. Flood and
- G. M. Halloran2
There have been a number of reports indicating that, in the absence of vernalization and photoperiod influences, there is a factor(s) which acts to exert control over the rate of development in bread wheat (Triticum aestivum L. em. Thell.). In an attempt to characterize this phenomenon more fully, three sets of wheat genotypes were examined for their rate of development in the absence of vernalization and/or photoperiod influences. Seventeen spring wheats, prevernalized and grown with an 18-h photoperiod in an outdoor pot experiment were found to differ in development rate, indicating that it may be of significance to adaptability and yield, at least in this type of wheat. In a set of near-isogenic lines of ‘Triple Dirk’ (differing for the vernalization response genes vrn 1 and vrn 2) their development rates were similar, indicating that it is not a manifestation of the action of genes for vernalization response. Additionally, the absence of a close correlation between the level of vernalization response and basic development rate in the 17 spring wheats indicates physiological independence between the two processes. Using growth apex dissection the various phases of floral development were followed in two Australian spring wheat cvs., Pinnacle and Falcon, at four times of sowing in an outdoor situation and grown under an 18-h photoperiod. The cv. Falcon was much faster than Pinnacle from sowing to floral initiation, terminal spikelet, and ear emergence at the four times of sowing. While the vegetative phase in Pinnacle was generally longer than in Falcon, the spikelet initiation and stem elongation phases did not show the same relative prolongation. ‘Chinese Spring’/‘Thatcher’ chromosome substitution lines 7B and SD, pre-vernalized for weekly periods from 0 to 8 weeks and grown with an 18-h photoperiod in an outdoor pot experiment were used to investigate the chromosomal control of development rate in wheat. Chromosome 7B of Thatcher substituted in Chinese Spring reduced its vernalization requirement and increased its rate of development. Chromosome 5D of Thatcher did not alter either vernalization response or rate of development of Chinese Spring. In view of these data and earlier reports, the term “basic development rate” is proposed to denote differences between wheats in the rate of development in the absence of vernalization and photoperiod influences. Recognition of the phenomenon of basic development rate prompts a re-evaluation of the developmental basis of flowering in wheat and other temperate plants.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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