22.07.2013 Views

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

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

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

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

inputs $rould be required, since they appeared to perform<br />

best under more idear growing c<strong>on</strong>diti<strong>on</strong>s. The semi_dwarfs<br />

were not as able to h<strong>and</strong>fe stresses åmposed by weed cornpeti_<br />

ti<strong>on</strong>, Ìow ferti_líty or drought. Although no fertilizer by<br />

genotype interacti<strong>on</strong>g occwred for yield or its major compo_<br />

nents, trends indicated that the short-statured naterial had<br />

a greater requírenent for at l_east the first increment <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

nitrogen relative to the tal1 genotypes. At the hígher<br />

nitrogen levels this extra resp<strong>on</strong>se did not c<strong>on</strong>tinue.<br />

fhe two semi-dwarfs whÍch performed best in this trial,<br />

C7o3o32 <strong>and</strong> Minn64-62, galned their yield primarily frorn<br />

producti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> more heads per unit area than the tatls. lfhey<br />

had fewer kernels per head <strong>and</strong> lower kernel weight at most<br />

sltes. Inereased N díd al"leviate some <str<strong>on</strong>g>of</str<strong>on</strong>g> these d.ifferentials<br />

when growing c<strong>on</strong>diti<strong>on</strong>s were adequate ¡ however. kernel weight<br />

$ras least favourable at the hÍghest yield 1evels.<br />

0n the average, Minn6&_ó2 was the highest yieldång<br />

genotJæe. ¡iowever, its drawback was its lateness, since,<br />

except under good growing c<strong>on</strong>diti<strong>on</strong>s, it was unabre to c<strong>on</strong>plete<br />

its growing cyc1e, resur,ting ín greatry <str<strong>on</strong>g>reduced</str<strong>on</strong>g> kernel<br />

size "<br />

When lodging oecurred, the semi_dwarfs exhibited<br />

superior resistance, which c<strong>on</strong>tinued as the fertility level<br />

increased. The gap between the lociging levels <str<strong>on</strong>g>of</str<strong>on</strong>g> the tall<br />

<strong>and</strong> short types increased with N level, particularly for<br />

mírn64-62, which showed no increase ln degree <str<strong>on</strong>g>of</str<strong>on</strong>g>, lodging as<br />

N inereased.<br />

238

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!