Effects of reduced plant height on breeding requirements and ...

to control wild oats at Carman was partly responsible.
Carbyne is known to eontroL the wÍld oats by setting them
back and thereby decreasing their competitive ability wlth
the crop. High fertility enhances this effect, (8.H. Stobbe,
personal co¡nmunicatíon ) o and therefore the more fertile
treatments in the study grew taller because they were less
affected by the wild oats.
?he shorter <strong>height</strong>s <strong>of</strong> all genotype s at a1l N levels at
Carman reflected the less than ideal growing conditions, due
to drought and weeds, and. the lower initial levels <strong>of</strong> availl -
able N at thãt site. lhe mid and. late season drought at
Portage in 19?6 probabry caused the snaller amount <strong>of</strong> he ight
variatíon there' arthough there may have been other contríbuting
faetors "
Since there was generally no fertiLizer by genotype
(¡ x c) interaction for <strong>height</strong> we assume thåt the shortness
<strong>of</strong> straw, relatíve to the tall genotypes, uras maíntained as
applied N increased. On the other hand, <strong>height</strong> increased
with added N, meaning the heíght <strong>of</strong> the semi-dwarf,s increaseir
as well as that <strong>of</strong> the talls. This might reduce their lodging
resístance" fhe significant intêraction at portage in L975,
occurred beiause cz030l1 and, cla)oJ7 showed a tendency towards
greater <strong>height</strong> íncreases as applied N increased than diil
MLnn64-62, the other short genotype considered. fhe evidence
leads us to conclude that it would be ,r"""""u"y to evaluate
the lodging resístance <strong>of</strong> short strawed material despite the
strong relationship <strong>of</strong> this trait with <strong>plant</strong> <strong>height</strong>, part-
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