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

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<strong>and</strong> the treatments which increased the number <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>plant</str<strong>on</strong>g>s per<br />

unit <str<strong>on</strong>g>of</str<strong>on</strong>g> row length showed j_ncreased <str<strong>on</strong>g>height</str<strong>on</strong>g>, with B<strong>on</strong>anza the<br />

more resp<strong>on</strong>sive" rrt carrnan, the combined effeets <str<strong>on</strong>g>of</str<strong>on</strong>g> rate<br />

seeding, drought <strong>and</strong> early weed infe stati<strong>on</strong> gave the opposite<br />

effect, wíth both genotypes resp<strong>on</strong>ding <strong>and</strong> the widest row<br />

spacing having the shortest prants. The eãrly weed infestati<strong>on</strong><br />

whlch rimited growth <strong>and</strong> utilized rnuch <str<strong>on</strong>g>of</str<strong>on</strong>g> the available<br />

moisture appeared to be the rnain cause <str<strong>on</strong>g>of</str<strong>on</strong>g> this reacti<strong>on</strong>.<br />

The lack <str<strong>on</strong>g>of</str<strong>on</strong>g> sigrrificant seeding rate effects dem<strong>on</strong>stra_<br />

ted the ability <str<strong>on</strong>g>of</str<strong>on</strong>g> the rnaterial to compensate for those<br />

differences. However, under stress c<strong>on</strong>dití<strong>on</strong>s at Carman<br />

the semL-dwarf showêd a trend towards taller <str<strong>on</strong>g>plant</str<strong>on</strong>g>s at the<br />

highest seeding rate, while B<strong>on</strong>anza had the g:.eatest <str<strong>on</strong>g>height</str<strong>on</strong>g><br />

at the intermediate seed rate. Thís suggested that the<br />

semi-dwarf may require higher seeding rates when grown under<br />

stress. At Winnipeg, under very ideal c<strong>on</strong>diti<strong>on</strong>s, B<strong>on</strong>anza<br />

was tallest at the lowest seeding rate, whi.Ie Mírn64_62<br />

showed no <str<strong>on</strong>g>height</str<strong>on</strong>g> differenee across seeding rates.<br />

The very short stature <str<strong>on</strong>g>of</str<strong>on</strong>g> Minn64-62 under the stress<br />

c<strong>on</strong>dÍti<strong>on</strong>s at Carman raises the questi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> whether such a<br />

heíght may be too short for. practical purposes. Such a<br />

very short genotype might, under adverse c<strong>on</strong>diti<strong>on</strong>s, be less<br />

desirable than <strong>on</strong>e <str<strong>on</strong>g>of</str<strong>on</strong>g> an intermedj.ate <str<strong>on</strong>g>height</str<strong>on</strong>g> Ín terrns <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

suitability for modern harvesting procêdures.<br />

Yield<br />

It is c<strong>on</strong>sidered important to deternÍne whether such a<br />

2L4

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