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Although some crosses between Aegilops squarrosa and common
wheat were obtained recently by some workers (Gill and Raupp 1987;
Cox et al. 1990), hybridization between wheat and Aegilops
squarrosa is still difficult. Genetic analysis on the
crossability of wheat with Aegilops squarrosa would provide
useful information not only for practical breeding, but also on the
genetics and evolution of wheat (Koba and Shimada 1993).
Krolow (1970) revealed that tetraploid wheat, like the hexaploid
wheat, has the Kr system which regulates hybrid kernel set in
wheat x rye crosses. Halloran (1981) reported that mutation(s) in
wheat from high to low crossability with rye took place at least as
early as the tetraploid level of wheat evolution. Scoles (1983) found
that the genotype used in the cross affected both hybrid endosperm
and embryo development, when tetraploid and hexaploid wheats were
crossed with different inbred lines of Secale cereale.
The objective of this study was to determine if specific chromosome
replacement can affect the crossabilitv of durum wheat with Secale
cereale and Aegilops squarrosa.
Materials and methods
A set of 14 disomic substitution lines, in which each of A and B
genome chromosome pairs of durum wheat (Triticum turgidum ssp.
turgidum conv. durum) cultivar Langdon was replaced by a
homoeologous pair from the D-genome of Chinese spring, was kindly
provided by Dr. L.R. Joppa, North Dakota State University, Fargo, ND,
USA. These disomic substitution lines and Langdon, were used as
female parent in crosses with rye, Secale cereale L. (a
diploid open pollinate Turkish landrace).However, these disomic
substitution lines and Langdon were used as male parent in crosses
with Aegilops squarrosa (collected from Azerbejcan and,
obtained from ICARDA, Accession no: 400630). The crosses were made in
field conditions in the 1994-95 growing season.
Emasculation and pollination were made in the early morning between
7.00 and 10.00 am, emerging spikes of wheat were selected for
emasculation in field conditions. Emasculated spikes were bagged with
parchement bags and checked in the next morning. When the stigmas
were fully receptive, mature anthers were taken from Langdon and rye
just before the bursting of the pollen sacs, and at least one anther
was carefully placed on each stigma of Langdon and Aegilops
squarrosa spikes. The spikes were harvested at maturity.
Crossability percentages were estimated as the ratio of the number of
kernels set to number of florets pollinated. The hybrid kernels were
germinated on wet filter paper in petri dishes at 22C and numbers of
germinating seedlings were scored six days later.
The t-test was adopted to detect the Crossability differences between
D-genome substitution lines of Langdon and Langdon (control) with
rye. Also, this statistical analyses were carried out by using
transformed values to angles of the percentages in individual
spikes.
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