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Selection for fertility in the original TRC population might have been
effective (Table 1) since the random population
had slightly lower fertility than the 41 selections (61.8 vs. 67.4%),
slightly higher variance in fertility, and smaller range. Further selection
for fertility will be made at Davis while maintaining the winter-type
background. At present the TRC lines have lower fertility than most standard
varieties. If high fertility lines can be selected under Davis conditions,
it is likely that their fertility levels would be high in areas where
winter types are adapted. TRC will also be maintained as a bulk population
to allow further recombination to occur. Intercrossing among fertile lines
may be required to obtain maximum restoration. Small quantities of seed
of the bulk or selected lines are available on request.
Restoration of Triticum zhukovskyi and Primepi
Primepi was crossed to cms Ramona and the F1 plants had 50.4% fertility
(based on three plants with four spikes each). Primepi itself is very
late at Davis and to be useful, pollen fertility restoration from this
variety should be introduced into a photoperiod insensitive background.
A Justin-type restorer line, obtained from K. LUCKEN, North Dakota State
University, with pollen fertility restoration genes from T. zhukovskyi
showed quite high fertility at Davis. In a cross with cms Ramona 50 the
F1 fertility was 70.0% (based on three plants with four spikes
each). Additional observations will be made on restoration in this material.
Seed set on cytoplasmic male sterile plants
Conversion of varieties to cytoplasmic male sterile forms is in progress
using the T. timopheevi cytoplasm at Davis. Early generation materials
from this program and lines received from other workers were used to judge
the general level of outcrossing under nursery conditions. Random open
pollinated spikes were taken from cytoplasmic male sterile rows which
had at least one male fertile border row. The plants were spaced 30 cm
within rows which were 30 or 60 cm apart. The sample included a range
of heading time: early and late spring wheats and winter wheats. No seed
set has been obtained from bagged cms plants at Davis. From the data of
Table 2 it is apparent that outcrossing did
not differ greatly depending on time of anthesis. The late flowering winter
types had 18% mean seed set and the spring types were similar with a mean
of 17% seed set. These results indicate that considerable care will be
required to develop pollination blocks with high crossing rates at Davis.
(Received October 13, 1969)
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