OREGON
OREGON STATE UNIVERSITY
Crop and Soil Science Department, Corvallis, OR 97331-3002 USA.
Preharvest sprouting tolerance of a synthetic hexaploid
wheat (Triticum turgidum / Aegilops tauschii).
A.C. Rosa and W.E. Kronstad.
Two studies evaluated the preharvest sprouting tolerance (PST)
of a synthetic hexaploid wheat (Altar 84/Ae. tauschii)
and to investigate its potential as a source of PST in crosses
with selected wheat cultivars.
The first study compared the synthetic hexaploid wheat with selected
wheat checks for PST and with its durum wheat parent (Altar 84)
for the germination response of these genotypes to controlled
wetting treatments applied to field-grown intact spikes and threshed
seed. Spikes were rolled in wet germination paper, and the percentages
of germinated seed were determined after 7 days. Threshed seeds
in petri dishes were wetted with water and vegetative floral tissues
(chaff) extracts. Germinating seeds were counted daily for 14
days. RL-4137, Frontana, and BR-35 were more tolerant than the
synthetic. The synthetic was more tolerant than Altar 84 and Bacanora
88 and was as tolerant as the moderately sensitive cultivar BR-23.
The improved PST of the synthetic over Altar 84 was attributed
to Ae. tauschii. Seed dormancy and water-soluble substances
in the chaff of the synthetic and other genotypes appeared to
contribute to their PST.
The second study used random inbred F5 lines obtained from single
and backcrosses between the synthetic (red-seeded) and the sensitive
wheat cultivars Opata 85 (red-seeded) and Bacanora 88 (white-seeded).
Seed-coat color and germination responses of the F5 lines subjected
to a 5-day spike wetting treatment were evaluated. Preharvest
sprouting tolerance was moderately to highly inheritable and largely
controlled by additive gene effects in the studied populations.
An association between red seed coat color and PST was observed,
but white recombinant lines more tolerant than their sensitive
parent were obtained. The synthetic was capable of improving the
PST of wheats with red and white seed coats. In order to utilize
the tolerance from the synthetic to breed for improved PST, the
use of the more tolerant lines obtained in this study as parents
in backcrosses to agronomically superior germ plasm is suggested
as an appropriate strategy.