|
I. Research Notes
Allelic variation at the crossability
loci in wheat (Triticum aestivum)
L.A. SITCH(1) and J.W SNAPE
PLANT BREEDING INSTITUTE, CAMBRIDGE, U.K.
The crossability of hexaploid wheat (Triticum
aestivum) with rye (Secale cereale) has been
shown to be controlled by three loci, designated
Kr1, Kr2 (LEIN 1943) and
Kr3 (KROWLOW 1970), located on chromosomes
5B, 5A (RILEY & CHAPMAN 1967) and 5D (KROWLOW 1970)
respectively. LEIN (1943) demonstrated that the dominant
alleles at the Kr1 and
Kr2 loci reduced crossability, with
Kr1 having a greater effect than
Kr2. A high positive correlation between
the crossability of wheat with rye and Hordeum bulbosum has
also been demonstrated (FALK & KASHA 1981, SITCH et
al. 1985, SNAPE et al. 1979) and genetic studies
involving comparisons of the crossability of the Chinese
Spring (Hope) single chromosome substitution lines (SNAPE
et al. 1979) and of recombinant lines for the
Kr1 locus, with rye and H. bulbosum
(SITCH et al. 1985) confirm that the Kr loci
control the crossability of wheat with both pollen
parents.
An examination of the H. bulbosum and the rye
crossability of the single chromosome substitution lines of
the non-crossable varieties, Hope, Atlas 66 and Cheyenne
into Chinese Spring, for all the homoeologous group 5
chromosomes by FALK & KASHA (1983) indicated that there
may be multiple alleles for reduced crossability on
chromosomes 5A and 5B. However, no evidence was found for
variation at the Kr3 locus on chromosome
5D of these varieties. The only significant evidence of a
third crossability gene was obtained by FEDAK & JUI
(1982), in pollinations of barley (Hordeum vulgare) cv.
Betzes with the Chinese Spring (Hope) substitution
lines.
This paper describes an investigation designed to ascertain
whether there is any evidence of multiple allelism at the
Kr loci of the non-crossable varieties Hope and
Capelle-Desprez and to determine whether different
Kr3 alleles exist in these varieties from
that in Chinese Spring, from a study of the H.
bulbosum crossability of the group 5 substitution lines
of these varieties into Chinese Spring.
Materials and Methods
The single chromosome substitution lines of the group 5
homoeologous chromosomes of the varieties Hope and
Cappelle-Desprez into Chinese Spring were produced by
Professor E.R. Sears, University of Missouri, Columbia,
Missouri, U.S.A. and by Dr. C.N. Law and Mr. A.J. Worland,
Plant Breeding Institute, Cambridge, England respectively.
SNAPE et al. (1979) demonstrated that these two donor
varieties are non-crossable with tetraploid H. bulbosum. All
H. bulbosum pollinations were made using the
tetraploid H. bulbosum clone PB168, originally
obtained from Dr. D.B.H. Sparrow, from the Turkey collection
CPI 18968, entry number 73/3.
The chromosome 5D substitution lines were vernalized for two
weeks, at 4C with an 8-hour daylength, to promote flowering
because both donor varieties possess winter alleles at the
Vrn3 locus on chromosome 5D controlling
vernalization requirement (LAW et al. 1976). The
H. bulbosum clones were vernalized under identical
conditions for 8 weeks to promote flowering, and grown,
together with the wheat genotypes, in an unheated glasshouse
during the summer.
All crossing procedures were carried out as described SITCH
et al. (1985) on 12 spikes per genotype. The percent
seed set was established for each spike individually and
then averaged over contributing spikes. The statistical
analysis was carried out using data transformed to
angles.
|