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

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while the tall sho\^/ed virtually no yield difference between<br />

]-39<br />

the narrowest <strong>and</strong> the intermediate spacings" Similar<br />

results v,¡ere reported from a wheat study b¡, Stoskopf (Lg6?) "<br />

Ä significant genotype x seeding rate x row spacing<br />

interacti<strong>on</strong> occurred at Õarman (ra¡re 56). This interacti<strong>on</strong><br />

wâs due to B<strong>on</strong>anza c<strong>on</strong>sistently outyielding the semi_dwarf<br />

at al-Ì levels <str<strong>on</strong>g>of</str<strong>on</strong>g> al_l seeding-rate - rovr'_spacing combinati<strong>on</strong>s<br />

except for the combinati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> the narrowe st row space <strong>and</strong><br />

the highest seedíng rate. At this treatment co¡nbinati<strong>on</strong><br />

Minn 64-62 outyierded B<strong>on</strong>anza by an amount equal to that by<br />

which the reverse had Õccurred at all other treatment<br />

co¡nbinati<strong>on</strong>s. This effect was probably due to the adverse<br />

growth c<strong>on</strong>diti<strong>on</strong>s at this site, resulting in particular<br />

stress <strong>on</strong> the seni-dwarf due to earty weed competiti<strong>on</strong>. At<br />

the narrow row spacing <strong>and</strong> higher seeding rate the semi_<br />

dwarf was able to compete with the weeds as well as the<br />

tal1 genotJrpe <strong>and</strong> thu.s yielded rnore grain at thât treatrnent<br />

combinati<strong>on</strong>. Similar results were reported from a ,¡rheat<br />

study (You.ng <strong>and</strong> Bauer, Ig?3),<br />

Spikes ner ünit Area<br />

At Sanford <strong>and</strong> lfinnipeg the semi-dwarf had significantly<br />

more spikes per unit area than the tall (Table 5B),<br />

In agreement with the findings <str<strong>on</strong>g>of</str<strong>on</strong>g> Guitar.d et q!. (]961)<br />

a positive effect <strong>on</strong> spikes per unit area resulted from<br />

íncreased seedì-ng rates (fable 59), atthough the ehange was

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