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

environnent. Àny eonclusion regarding whieh component has
the greatest effect on any other then nay have to do with
the potential "sink" <strong>of</strong> a given genotype or group <strong>of</strong> genotypes.
The eonplexity <strong>of</strong> these relationships may hâve been
compounded in the semi_dwarfs by li:rkage between kernef
weight and the semÍ-dwarf habit.
Yie 1"4_lÇomponent s
0vera11 the more successful semí-dwarfs appear to be
such because they have larger nunbers <strong>of</strong> spikes per unit
area, wh5"eh Íncreased with added N. In conjunctÍon with
this there was a reduction in spike size, but more seriously
a reduction in kernel weight. Frorn an end u_se standpoint
<strong>reduced</strong> kernel weÍght could not be tolerated and, since
maxinum yield wirr only be achieved by an efficient balance
anong the components, the semi_dwarfs must be aLtered to
improve kernel weight, even at the expense <strong>of</strong> the other yield
conponents provided that yield ean be maintarned or increased.
f,odsinE
îhe lodging encountered was the late season type eaused
by the inabÍlity <strong>of</strong> the straw to support filling and/or
filled spikes. Lodging can then be partially aecounted for
by yield level, with the higher yieJ"ding treatnents suffering
increased lodging. l{owever, the superíor lodging resistance
<strong>of</strong> the shorter strawed materÍar was elearry demonstrated at
Portage, where Minn64-62 díd. not lodge despite yielding as
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