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Results
The table of means of Chinese Spring and the six
substitution lines and the analysis of variance for seed
setting ability are shown in Tables
1 and 2 respectively. The
seven genotypes differed significantly in seed setting
ability. The seed set obtained on the 5A and the 5B
chromosome substitution lines of Hope and Cappelle-Desprez
was significantly lower than that obtained on Chinese
Spring. The crossability of the 5D substitution lines,
however, was not significantly different from Chinese
Spring. This implies either that Hope and Cappelle-Desprez
possess an allelle of small effect at the third crossability
locus, Kr3, on chromosome 5D or that, in
these varieties, this locus is represented by an allele
equivalent to that of Chinese Spring.
The variation in crossability of the six substitution lines
was partitioned into the main effects of the three
chromosomes, of the two varieties and the interaction
between these two main effects, Table
2.
The overall crossability of chromosomes 5A, 5B and 5D
differed significantly, the 5D chromosome substitution lines
having the highest crossability and the 5B chromosome
substitution lines the lowest. The variation between
chromosomes was further partitioned to allow a comparison
between chromosome 5B and the remaining chromosomes, and
between chromosomes 5A and 5D. This indicated that a large
proportion of the variation in the overall crossability was
attributable to the severe reduction in percent seed set
caused by Kr1 on chromosome 5B. However,
the allele Kr2, on chromosome 5A, also
contributed towards this variation since the overall
crossability of the 5A substitution lines was significantly
lower than that of the 5D substitution lines.
An overall comparison of the crossability of the
substitution lines derived from Hope and from
Cappelle-Desprez showed that the mean of the group 5
chromosome substitutions did not differ significantly.
However, the significance of the interaction implies allelic
variation between the homoeologous chromosomes of Hope and
Cappelle-Desprez. A partitioning of this variation into a
comparison between chromosome 5B and the remaining
chrosomes, and between chromosomes 5A and 5D, revealed that
the allelic variation between Hope and Cappelle-Desprez was
attributable to allelic differences at both the
Kr1 and Kr2 loci. The
Kr1 allele on chromosome 5B of Hope was
significantly (p < 0.05) more potent than that of
Cappelle-Desprez in suppressing crossability. In contrast,
the Kr2 allele from Hope was significantly
(p < 0.05) less effective than that from
Cappelle-Desprez.
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