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

extent to which the observed variability is heritable and
therefore selectable. Such a measurement is termed heritability,
and, in the broad sense, is measured by the ratio
<strong>of</strong> the genetic variabilit¡' to the environmental varÍability
(A]lard, 1960). This measurement gives the breeder an indic-
ation <strong>of</strong> the method <strong>of</strong> selection most likety to succeed,
the sel-ection íntensity required in various generations and
the generation during which selection is most 1ikely to be
effective.
Heritability estimates for yield and other <strong>plant</strong>
characters have been calculated in several- crops (Fiuzat
and Atkins, Agfi). In general, characteristics such as
maturity and <strong>plant</strong> <strong>height</strong> have been reported to be highly
heritable, while yield and its related components have been
l-ow in heritability. It shoufd be noted that heritability
estimates in self-pollinated crops are dependant on: (1)
the generation in which they are neasured, since with increased
homozygositÍ, the non-heritable (dominant) fraction
<strong>of</strong> the genetie variance j-s decreased in cornparison to the
additive (heritable) fraction (Grafius et 41., 1952)¡
(2) the amount <strong>of</strong> geneti-e variability in the naterial
studied, and (3) the method used to cal-c ulate the genetic
variance and thus the herÍtability estimate (Frey and
Horner, !955).
Various ínvestigators have reported heritability
estimates for several characteristics in barley (fable 1).
Heritability estimates have generally been high for <strong>plant</strong>
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