- Concerns about the genetic control and environmental influence
of various stages of development including the grain filling period,
and the relationship between early maturity and grain yield prompted
The experimental material consisted of two facultative and two
winter wheat cultivars. A dial!el cross, excluding reciprocals, was
also developed to provide an Fl generation. Information was collected
for 14 traits and subjected to statistical analyses.
Genetic differences among varieties were found for time of
heading, flowering and physiological maturity, duration and rate of
the grain filling period, grain yield and yield components. The
facultative types, AI Feng 2 and Selection CB 83-52, showed earlier
heading, flowering and physiological maturity, longer lag period
(period between heading and flowering), and longer duration and lower
rate of grain filling, resulting in lower grain yield. The winter
cultivars, Stephens and Yamhill Dwarf, in contrast had later heading,
flowering and maturity, shorter lag period, and shorter duration and higher rate of grain filling, giving higher grain yield. For the
developmental stages after heading, larger differences were observed
in the lag period while differences in duration of grain filling
period were relatively small among the cultivars.
Depending on the specific Fl population, there was a tendency
toward dominance for early heading, a range from no to complete
dominance for early flowering and no dominance for physiological
maturity. Long duration and fast rate of grain filling were generally
Grain yield was positively associated with the number of days to
heading, flowering and physiological maturity. Also positive
associations of grain yield were obtained with tiller number, kernel
weight, grain weight per spike, biological yield and rate of grain
filling. Negative associations of grain yield were noted with lag
period and duration of grain filling period. No clear associations
between physiological maturity and the yield components were found.
Grain filling duration showed no association with yield components
while grain filling rate exhibited positive association with tiller
number and kernel weight. There was negative association between
duration and rate of grain filling period.
According to heading responses from different planting dates,
Stephens and Yamhill Dwarf had high sensitivity while Selection CB 83-
52 and AI Feng 2 showed low sensitivity to vernalization. Genotype X
environment interaction was observed with each cultivar responding
differently for several traits depending on the planting dates.