|Abstract or Summary
- Four, six-rowed, spring barley cultivars were used as
parental material in this study. The parents were distinctly different
in plant height. Washington-6124-62 is a standard height
selection while Short Wocus and Minn. 66-102 are intermediate.
The fourth parent was a dwarf selection obtained from India. The
two intermediate cultivars and the dwarf cultivar were crossed to
the tall parent, Wa-6124-62, with a portion of the F₁ progeny
backcrossed to the shorter parent. In addition, the intermediate
parent, Short Wocus, was crossed to Indian Dwarf. The following
generations were available for study: parents, BC₁F₁, F₁, and F₂.
The purpose of this study was to obtain information concerning
the inheritance of plant height and to determine when selection for this
trait could be made in the breeding program most effectively. To
achieve this objective heritability and the mode of gene action were
studied as well as number of genes segregating for plant height.
The effect of temperature on plant height was also investigated in a
growth chamber utilizing two temperature levels, 19° C and 30° C.
Plant height was recorded on an individual plant basis at two
sites that were distinctly different environmentally and in the growth
chamber. The number of nodes were counted, and the length of
internodes measured for genetic interpretation of culm length.
Broad sense heritability values for plant height of each cross
were estimated by using the variance of parents, F₁'s and F₂' s.
Heritability values were quite high in the F₂ generation ranging from
50 to 90 percent, and suggest that plant phenotype gave a relatively
good indication of the genotype for plant height.
Height of the F₁ plants was between the mid-parent and tall
parent indicating partial dominance for tall culm length.
In earlier studies, many investigators found that additive gene
action was the major component of genetic variability for plant
height. Results obtained from this study suggest that the nature of
gene action is a function of the parents used. Where large differences
exist between parents, plant height appeared to be largely
influenced by non-additive gene action. When the parents were
similar in height the trait was controlled mainly by additive gene
Fairly discrete height classes in the segregating populations
indicated that plant height was controlled by only a few genetic factors in these populations. Ratios obtained from segregating populations
suggested the presence of three recessive genetic factors
for short height in the dwarf parent (Indian Dwarf). The tall parent,
Wa-6124-62, and intermediate parent, Minn. 66-102, appeared to
differ for plant height by one major genetic factor.
Difference in height among the cultivars was mostly due to
difference in internode length rather than the number of nodes.
It was concluded that the rather simple inheritance of plant
height in barley will allow effective selection in the F₂ generation
for short stature, and progress to develop semi-dwarf barley
cultivars should be possible if stiffness of straw can also be obtained
along with short stature. In the cross between the tall and dwarf
parent, selection for intermediate plant height would be more effective
if delayed for several generations of selfing due to the relatively
large dominance component of genetic variance.