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

One <strong>of</strong> the problems which has existed with the seni-
dwarf $¡heat in the U.S.Â" has been poor ernergence due to
shortness <strong>of</strong> the coleoptile, shown to be associ.ated with
<strong>reduced</strong> <strong>plant</strong> <strong>height</strong> (Allan e.[ ål, 1962). This can present
a problem for the producer, particuÌarly if deep seeding is
requfred to reach moisture "
Despite the lack <strong>of</strong> a slgnifÍcant correlation between
<strong>plant</strong> <strong>height</strong> and coleoptile length for the genotypes studied
in the present experiment, the ranking data and significant
difference between <strong>height</strong> classes indicated that the tall
genotypes did have longer coteoptiles. However, due to the
strong positive relationshÍps between eoleoptÍle length and
the kernel size parameters, and the strong positive relation-
ships between these and. helght, the question arises as to
whether the <strong>height</strong> to coleoptile length relationship was
direct or l-ndirect. nhe results indicated that it was
posslbly indírect, èaused by the short statured genotypes
having smaller, lighter kernels. and therefore shorter
coleoptiles. This relationship could present further prob-
Lems as higher yÍelding serai-dwarfs are developed, since,
as shown ln experiments discussed earlier, the kernel size
component <strong>of</strong> yield suffered thê greatest reduction as overall
yíeld increased. This was particularly the case for the
higher yieldíng semi-d.warfs ín Experiment It.
Bhe positive assocåation in thís experiment between root
219