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

drastícaIIy changed phenotype as the seni_dwarf requires
ehanges in agronomic practics to maximize yield. The relative
yielding abilities <strong>of</strong> the specific genotypes investi_
gated were also <strong>of</strong> interest.
At Sanford and Winnipeg, where growing conditions were
adequate to ideal, Minn64-62 outyielded Bonanza by 6"0 and
1-4.0 percent over the whole <strong>of</strong> each experiment respectÍvely.
At Carman, where late seeding, drought and weeds led to very
poor growing conditions, Bonanza outyielded the semí-dwarf
by sorne IJ.O percent. fhese results suggest, as did those
<strong>of</strong> Porter et al. (fg64) with wheat, that the semi_dwarf nay
not be suited to growth under stress conditions, partic ularly
weed competition and drought. In the present rnaterial, this
is probabJ.y a result <strong>of</strong> generally poor competitive ability
due to slow and prostrate early growth and perhaps a less
extensive root system. However, under conditions <strong>of</strong> adequate
to good moisture and fertility, and r,rlith good weed control,
the semi-dwarfs may have a higher potential yíeld. Such
results are important relative to recornmendations to farmers
regarding the production <strong>of</strong> such semi-dwarfs.
As previously noted by others, seeding rates, particular-
1y <strong>of</strong> the narrow range used, affected yield only when conditions
were adverse. This was the case at Carnan, where
increased seeding rates gave hígher yields" Â similar,
though non-sÍgnificant, trend was shown at Sanford, but no
differences <strong>of</strong> consequence were shown under the more ideal
conditions at Winnipeg.
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