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Variation in growth, flowering, and
seed set under high temperatures in Aegilops species
B. EHDAIE and J.G. WAINES
Department of Botany and Plant Sciences, University of
California, Riverside, CA 92521, USA
Drought and heat are major environmental factors that reduce
rainfed wheat production in semiarid regions. While there
has been considerable effort to understand and improve
drought resistance in wheat, relatively little effort has
been made to increase knowledge about heat resistance
(MARSHALL 1982). Consequently, there has been little
improvement of resistance to heat stress.
The effect of temperature on wheat was studied under
controlled conditions (FRIEND 1966, BAGGA & RAWSON
1977). In these studies, only a few bread wheat genotypes
(Triticum aestivum L.) were tested. The existence of
heritable variation for heat resistance during early stages
of growth was reported in bread wheats and durum
wheats (T. durum) (SISODIA et al. 1978, KANANI
& JADON 1985). Reports of the effect of high
temperatures on wild relatives of wheat are limited. This
preliminary experiment was undertaken to study the responses
of different accessions of the D genome (Aegilops
squarrosa L.) and the B genome (Sitopsis group of
Aegilops) to high temperatures in the field during
early stages of growth as well as during reproductive
stages.
Materials and Methods
A total of 389 plants belonging to Ae. squarrosa (15
accessions), Ae. speltoides ssp. speltoides
(13 accessions), Ae. speltoides ssp. ligustica
(5 accessions), Ae. bicornis (11 accessions), Ae.
longissima (12 accessions), Ae. sharonensis (7
accessions), and Ae. searsii (10 accessions) from the
University of California, Riverside, germplasm collection
along with 5 tetraploid and 5 hexaploid wheat genotypes were
grown in the field during Summer 1987. The tetraploid
genotypes, Mexicali, Nos. 18, 62, 82, and 94, and the
hexaploid genotypes, Anza, Yecora Roja, Sholeh, and Nos. 14
and 69, involved Mexican semidwarf Californian cultivars and
landraces from southwestern Iran. Seed were sown in flats in
the greenhouse on June 16, and seedlings were transplanted
in the field on July 22. Each accession had 4 to 10 plants.
Plants were irrigated frequently to prevent moisture stress.
The number of plants which survived during early stages of
growth was recorded for each species and subjected to
chi2 analyses to compare the survival rates,
i.e., the number of plants that survived to total number of
plants, of different species under heat stress. The number
of plants that flowered and produced seed was also recorded.
Agronomic characteristics of the promising heat-resistant
accessions were measured.
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