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

trial period. The area in which the triars were condueted
tended to have a hot dry period at the time the material was
naturi.ng. lhese conditions forced earlier naturity, and the
later heading lines had grain filling terminated prematurely.
llence, lines which headed, and therefore f loì¡re¡ed, earl!.er,
were subjected to less heat and moisture stress for more <strong>of</strong>
their filLing period than lines which headed later.
Ehe positive yÍe1d to post-anthesis association would
be expected since post-anthesis is essentially a neasurement
<strong>of</strong> the graín development stage, and the longer this period
is, the more fully developed the graÍn should be. However,
neither kernel weight nor plumpness, both positively assoc_
iated with days in post-anthesis, were significantly correlated
with yield.
Apparently the yield to post-anthesis relationship
occurred as did the yieLd to heading association. fn fact,
on an individual basís, only those populations showing a
significant negative yield to heading relationship showed
the corresponding yleld to post-anthesis assocÍation. ThÍs
is not surprising as days to headíng is used in the calcula_
tion <strong>of</strong> days in post-anthesis. These results suggested that
measurement <strong>of</strong> days to heading nay be <strong>of</strong> greatest value when
selecting for high yieldÍng 1ines destined for prod.uction
under conditions similar to those encountered in this study,
particularly when large kernel sÍze is a desired eharacter.
The posítive correlation <strong>of</strong> lodging with yíelcl occurred
primarily because lodging was an effect rather than a cause.
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