| Vernalized seedlings plus an unvernalized set (germinated five days before
the end of the vernalization treatment) were planted in the same soil mixture
described above. Ten seedlings (five per pot) of each vernalization treatment
per line (0, 4, 6 and 8 weeks) were planted in 18 cm diameter pots. The
experiment was placed outdoors in early December 1981 under 18 h photoperiod
(natural photoperiod extended to 18 h by 150 W incandescent lights operated
through a time clock) so that photoperiod would not limit development rate
of the wheat. Minimum daily temperatures for the duration of the experiment
were above those necessary for vernalization. Records were made of the number
of days from planting to ear emergence on the primary tiller of each plant
and an analysis of variance was performed on the data. Results Significant (P=.01) differences in days to ear emergence at 0 and 8 weeks vernalization for all the wheats indicates the general presence of vernalization response amongst them. However, for those wheats showing only small differences in days to ear emergence between 0 and 8 weeks vernalization, e.g., in Triple Dirk and Thatcher, the presence of a vernalization response may be questioned because of possible differences in the developmental stage between the 0 and 8 weeks treatments at the time of planting out. However, part of the difference in days to ear emergence between 0 and 8 weeks vernalization for Triple Dirk D (5.2 days) is likely to represent an influence of vernalization because Triple Dirk D possesses the vernalization-promoting gene vrn 2 while Triple Dirk possesses the gene Vrn 2. On this basis it appears that all of the Australian wheats in this study with the exception of Halberd, possess a vernalization response. In some of the wheats the absence of a significant (P=.01) difference in days to ear emergence after 6 and 4 weeks vernalization indicate that their responses were satisfied by at least four weeks vernalization and in the remainder, except Sherpa, by six weeks cold treatment. Sherpa was the only wheat to exhibit a significant reduction in days to ear emergence from the six to eight weeks vernalization treatment. Many of the wheats were significantly (P=.01) different from each other in days to ear emergence at 0 weeks vernalization, which cannot be interpreted as solely due to differences in vernalization response between them. The existence of significant (p =.01) differences between some of the wheats in days to ear emergence after eight weeks vernalization, when the vernalization response of each line had been satisfied, indicates the possible presence of another factor(s), other than vernalization and photoperiod, influencing the time to ear emergence. |
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