| Results Differences in days to ear emergence of unvernalized plants of the different genotypes grown under long photoperiods is largely a measure of their relative vernalization responses. On the other hand differences in days to ear emergence in vernalized and unvernalized genotypes grown under long day would be a measure largely of their actual vernalization responses. The F2 population of the Condor x Sunset cross (both spring wheats) shows transgressive segregation for days to ear emerience beyond the later parent Condor in both the vernalized and unvernalized conditions under long day (Tables 2 and 3). The vernalized and unvernalized F2 populations had similar distributions and the mean value for the two populations differed by only 3.2 days indicating the presence of very little vernalization response. Days to ear emergence in unvernalized F2 plants of the cross Condor x Thatcher grown under long day had a range intermediate between the two parents but vernalized plants grown under the same daylength thowed transgressive segregation for delayed ear emergence. Again the difference in mean days to ear emergence between the two vernalization treatments (ca. five days) of the F2 population indicates the presence of a small vernalization response. The response of vernalized plants to a short photoperiod is an indication of the effect of photoperiod on delaying ear emergence in the absence of vernalization influences. Under these conditions the whole F2 population of Condor x Sunset again showed transgressive segregation for delayed ear emergence (Table 4) possibly due to increased photoperiod sensitivity as indicated by a comparison between this treatment and vernalized plants grown under long day (Table 2). The F2 population of Condor x Kogat showed some transgressive segregation for increased photoperiod sensitivity (Table 4) but that of Condor x Thatcher was intermediate between the two parents for days to ear emergence (Table 4). Unvernalized plants grown under the short photoperiod (normal daylength) give an indication of the interaction of vernalization and photoperiod in controlling ear emergence (Table 5). In this environment 18 of 30 plants of the F2 population of Condor x Sunset showed transgressive segregation for delayed days to ear emergence and in the Condor x Kogat cross only 1 out of 23 plants was later to ear emergence than both parents (Table 5) The F2 population of Condor x Thatcher was intermediate between the two parents for days to ear emergence. None of the three F2 segregating populations in any of the four treatment combinations (Tables 2 to 5) showed segregation into early and late types that would be consistent with simple inheritance. There was a close relationship between mean days to ear emergence and mean spikelet number in the four parental varieties (Table 6) with spikelet number being lowest in the vernalized, long day treatment and highest in the unvernalized, short day treatment. In the F2 populations of the three crosses differences in days to ear emergence between vernalized and unvernalized treatments were small (i.e., no vernalization response) under both long and short photoperiods and this was reflected in small differences in spikelet number. Short compared with long photoperiod gave substantial increasese in spikelet number (Table 6). |
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