| Summary: | The lack of information regarding the inheritance of the duration and rate of
grain filling, and the possible relationship between grain fill and grain protein
content in wheat prompted this study.
Early maturing Chinese cultivars, 'AI Feng 2' and 'CB 83-52', and late
maturing cultivars adapted to Oregon, 'Stephens' and 'Yamhill Dwarf', were
examined for vernalization and photoperiod responses. Progeny from a diallel cross
of the genotypes was evaluated for grain filling parameters, grain protein content and
other agronomic traits for two years.
'Yamhill Dwarf' required six weeks of vernalization, while other cultivars
needed only four weeks. The two Oregon developed genotypes were more sensitive
to photoperiod than Chinese genotypes. Variation in developmental patterns among
genotypes was related to differences in leaf number, spikelet number, rate of spikelet
initiation, and rate of grain fill. Compared to solid planting, space-planting reduced
the grain filling period.
Significant genotypic variation for grain filling rate, duration, and kernel
weight was observed in both seasons. Genotype X year interaction was not
significant for any of the grain filling traits. General combining ability effects for
grain filling rate, duration, and kernel weight were much larger than specific
combining ability effects. Additive gene action made the major contribution to the
inheritance of the grain filling traits. However, dominance effects appeared also to
be involved in the genetic control of grain filling duration and kernel weight.
Narrow sense heritability estimates were high for all three grain filling traits.
Results indicated that early generation selection for both duration and rate of grain
fill should be effective in these populations.
Rate, but not duration of grain fill was closely associated with kernel weight.
There was an inverse relationship between duration and rate of grain filling. Kernel
protein percentage was positively associated with duration, but negatively related to
rate of the grain filling. Results suggest that starch and protein accumulations in the
kernel are two highly independent processes and may not necessarily compete for
assimilates or energy. It may be necessary under the environments of this study to
increase the duration of the grain fill to obtain high protein content with acceptable
grain yield. === Graduation date: 1993
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