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

new era in rice research and production. Again the purpose
<strong>of</strong> the shorter straw was to allow more intensive use <strong>of</strong>
farm inputs, especÍally nitrogenr to increase grain yields.
Semi-dwarf rice varieties have Led to as much as double the
yields <strong>of</strong> the older standard <strong>height</strong> cultívars in sone areas
<strong>of</strong> Asia.
Short-strawed wheat and rice genotype s have been suc-
cessful- primarily due to their improved lodgíng resistance
under conditions <strong>of</strong> both high fertílity and moísture
(Briggle and Vogel, 1p68¡ Chand3er, 1969). Nevertheless
Briggle and Vogel (1968) índicated that the semi-dwarf
wheats did have some inherent yÍeld advantage as wel-l.
Success with wheat and rice prompted researchers in
other crops to look for a similar avenue <strong>of</strong> irnprovement.
Mutants produced by irradiation have been the prímary source
<strong>of</strong> short straw in barley. Among released semi-dwarf barley
varÍeties are "Midas" developed in the United Kingdom,
<strong>of</strong>fering a potential ten percent yield advantage over other
varieties at the t j-rne <strong>of</strong> its release (World Crops, L969),
and "Deba Abedr', a Danish variety <strong>of</strong>fering greater response
to nitrogenous fertilizers as conpared to sirnilarly adapted
standard eultivars (Kirby, 1968 ) .
Konishi (L9?6) indicated that the main barley growing
areas <strong>of</strong> Japan are occupied by semi-d.warf cultivars with
the "uzun gene giving them all a semi-brachytic growth
habit. The most common Japane se variety <strong>of</strong> this type is
"Akashinriki".
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