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| Abstract or Summary |
- The purpose of this study was to determine the amount of
heterosis in three complex traits in barley and to investigate the
concept of component interaction as a means of producing heterosis.
The complex traits were grain yield, total leaf area, and malting
quality.
Seven varieties of spring barley were crossed in all possible
combinations in the spring of 1963, The following year, the 21 F₁'s
and seven parental varieties were space planted in a replicated,
randomized block design in a greenhouse groundbed on the campus of
Oregon State University. Since three of the seven parents were six-rowed
barleys (Hordeum vulgare L., emend. Lam) and four were two-rowed
barleys (Hordeum vulgare L., emend. Lam) , crosses within
and between six-rowed and two-rowed barleys were included in this
study. The 21 crosses were separated according to their respective
parental row numbers throughout this study.
The evaluation of heterosis for the complex traits was made by the component approach. The amounts of heterosis for the complex
traits were related to the expression of heterosis of their components.
The association between components and the complex traits
and between the different components, were determined by computing
simple correlation coefficients. The direct and indirect relationships
of the components to the complex traits were further analyzed
by path coefficient analyses. Estimates of the type of gene action
present for the complex traits, as well as for their respective components,
were made by computing general and specific combining
ability estimates and narrow-sense heritability estimates.
Heterosis may occur in a complex trait even though none of the
components of the complex trait exhibit heterosis. This situation
has been called component interaction. When parental varieties do
not differ in the complex trait but possess large differences in
the components of the complex trait, component interaction may occur
in the hybrid to produce heterosis in the complex trait. Additive
expressions for the components in the hybrids of such parental
varieties may result in the hybrids exceeding both parents in the
complex trait.
Large differences in the components of the three complex
traits were found to exist among the parental varieties in this
study while the parental varieties were not greatly different in
the complex traits. These findings would suggest that component
interactions were likely to occur in the hybrids produced by
crossing the parental varieties. However, in this study, the expression
of heterosis for the three complex traits was limited, with only a few crosses expressing a substantial amount of heterosis.
The lack of heterosis, particularly in those crosses where the
largest differences in the components existed between the parental
varieties, could be ascribed to the failure to obtain an additive
expression in the hybrid for the most important components. The
relationships between the components of the complex traits also
indicated that the components were not completely independent. The
lack of independence of the components could also prevent component
interactions. There were several crosses which did exhibit component
interaction in the expression of heterosis for the complex
trait but these were relatively few in comparison to those which
did not exhibit component interaction.
Estimates of gene action, in general, were in agreement with
the observations of heterosis. Those traits which exhibited the
most heterosis were found to be controlled mainly by non-additive
gene action white those traits exhibiting a slight amount of heterosis were found to have large additive gene action estimates associated
with them.
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| Peer Reviewed |
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| Digitization Specifications |
- File scanned at 300 ppi using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 5.0 was used for pdf compression and textual OCR.
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Previous issue date: 1966-03-03
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