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Results
Monosomic analysis for total floret number per spike
The large number of florets per spike of 10-A was found to be
controlled by six pairs of genes, located on the chromosomes 5A, 7A,
1B, 2B, 2D and 6D (Table
1). However, it
should be noteworthy that the three pairs of genes on the chromosomes
2B, 2D, 6D could have much stronger effects than other three pairs of
genes on the chromosomes 5A, 7A and 1B in governing this character.
Chinese Spring, Abbondanza and 10-A had 114 plus or minus 2,106 plus
or minus 3 and 176 plus or minus 5 florets per spike of mean values,
respectively, whereas the mean values of floret number per spike of
the two
F1 disomic
hybrids were 144 and 140 (Table
1), respectively,
so the large number of florets per spike of 10-A should be controlled
by the multiple nondominance genes.
Monosomic analysis for sterile floret number per spike
The genes controlling the high number of sterile florets per
spike of 10-A were found to be carried on the chromosomes 1 B, 2B, 2D
and 6D (Table
2). Of these four
pairs of genes, the genes on chromosomes 2B and 2D have much stronger
effects than the gene on chromosome 1B which has stronger effect than
the gene on chromosome 6D in this character. Chinese Spring,
Abbondanza and 10-A had 33 plus or minus 4, 24 plus or minus 3 and 97
plus or minus 6 sterile florets per spike of mean values,
respectively, but the two F1 disomic hybrids had 55 and 41
sterile florets per spike of mean values (Table
2), respectively,
so the genes for the high number of sterile florets per spike of 10-A
should be also multiple but partially recessive inheritance.
Discussion
The effect of chromosomes on the total floret number per spike of
common wheat was not found to be reported in the past literatures,
but the genes controlling the sterile floret number per spike of
common wheat were located on the chromosomes of groups 2 and 6 (Sears
1954) and chromosome 4A (Driscoll 1975, Barlow and Driscoll 1981). In
this experiment, the large number of total florets per spike of 10-A
was found to be controlled by the chromosomes 5A, 7A, 1 B, 2B, 2D and
6D, but the genes on chromosomes I B, 2B, 2D and 6D might mainly
control the high number of sterile florets per spike. In other words,
these genes on chromosomes I B, 2B, 2D and 6D could have
pleiotropism. This is the obstacle to hardly overcome in the breeding
projects of increasing grain number per spike. It was fortunate that
the chromosomes 5A and 7A increasing the number of total florets per
spike did not carry the genes governing the high number of sterile
florets per spike, so the chromosomes 5A and 7A of 10-A could provide
the favourable genetic resource for wheat breeding of increasing
grain number per spike. In fact, some improved strains derived from
10-A have 150-160 florets per spike and only 20-30 sterile floret per
spike, and 120-130 grains per spike which is very higher than that of
the popular variety Mianyang-11 with 60-70 grains per spike (Zheng et
al. 1992). From theoretical and practical aspects, it has been shown
that 10-A is an excellent parent in wheat breeding, projects of
increasing grain number per spike.
References
Barlow KK and Driscoll CJ (1981) Linkage studies involving two
chromosomal male-sterility mutants in hexaploid wheat. Genetics 98:
791-799.
Driscoll CJ (1975) Cytogenetic analysis of
two chromosomal
male-sterility mutants in hexaploid wheat. Aust J Biol Sci 28:
413-416.
Sears ER (1954) The aneuploids
of common wheat.
Missouri Agr Exp Sta Res Bull. 572, pp59.
Yen C, Zheng YL and Yang JL (1993) An ideotype for high yield
breeding, in theory and practice. In: Proc 8th Int Wheat Genet Symp
(in press).
Zheng YL. Yen C and Yang JL (1992) Study on the genetic improvement
and utilization of
the common wheat
multispikelet line10-A. In: New Ways and
Technologies
of Genetics and
Breeding. pp 56-63.
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