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

(Table t5t) ind.icated that the first increroent gave a
significant response at atl sites, whereas the seeond
increment produced a further significant yield increase
in onÌy the two tests at CarûÌan.
Significant genotypic differences for yield vrere
obtained in all" tests except the one at Carman ín L9?5
( f a¡le 1¿{., ljiA ) , Àt three <strong>of</strong> the se f our locations the
tall genotypes were higher yie ld.ing than the semí-dwarfs
on a mean basis (Table 158). However, as shown in Table
IJA, at no site was the yietd <strong>of</strong> Minn 64-62 signifieantly
lower than that <strong>of</strong> the talls¡ in fact, síngle degree <strong>of</strong>
freedom comparisons (faul"e 1&) indicated Minn 64-62 ta øe
sígnificantly higher yielding than the tall control genotype
cv. Bonanza at Portage in I)16, The lower semi-dwarf mean
yield resulted from the overall lower yield.s <strong>of</strong> CfOl011
and C7O3o32"
ljnlike the report <strong>of</strong> Gardener and Rathjen (19?5), tfre
present study showed no F x G j-nteraction at any site (fa¡le
14). However, there was a trend. for the serni-dwarfs, C?03011
anð. C?O3O32, to show a greater respo.rìse and./ or need for at
least the first nitrogen increment. rt,t higher N 1evels this
response did not continue, possibly d.ue to another 1ímiting
factor, in this case moisture. Such lack <strong>of</strong> interaction
was previously reported by Syme ftgAZ ) in wheat. The
importance <strong>of</strong> moisture in the expression <strong>of</strong> nitrogen
response was reported by Stanberry and Lowrey (tSøS),
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