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Wheat Information
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Number 78: 18-20 (1994)
Breeding
behaviour of monosomics in hexaploid wheat
D. Singh and C. Rajlakshmy
Division of Genetics, Indian Agricultural Research Institute, New
Delhi 110012, India
All the monosomic lines of the wheat cultivar Chinese Spring,
developed by E.R. Sears, and twenty monosomic lines (excluding 5B) of
the Indian wheat variety Pb. C591, developed by Swaminathan et al.
(1968) have been maintained at the Division of Genetics, Indian
Agricultural Research Institute , New Delhi. These monosomic series
have been utilized in genetical and cytogenetical studies (Joshi et
al. 1968, Joshi and Singh 1979, Singh and Joshi 1979, Singh and Joshi
1986, Singh 1992).
Breeding behaviour of all the monosomic lines in the above two series
was studied for a period of eighteen years. Data pertaining to
variety Chinese Spring revealed that out of the 617 plants analysed,
65.6% were monosomics (20"+1'), 36.6% disomics (21"), 0.5% double
monosomics (19"+2') and 0.5% were nullisomics and trisomics (20" and
20"+1''' or 21"1') (Table
1). Similarly out
of 573 plants analysed in variety Pb. C591, 69.6% were monosomics,
29.3% disomics, 0.5% double monosomics and 0.5% nullisomics and
trisomics (Table
2). The
frequencies of monosomics and disomics in the selfed progenies of
monosomic lines in these varieties were well within the range (49 to
85% of monosomics and 11 to 29% of disomics) shown by Morris and
Sears (1967). Low frequencies of nullisomics and trisomics obtained
in the monosomic lines of the two varieties could be due to the fact
that only healthy plants were selected for cytological analysis,
expecting that identified monosomics could be effectively used in
crossings and for maintenance of monosomic lines.
Person (1956) reported a low frequency of double monosomics (0.4%) in
a population of 225 monosomics. A similar frequency of double
monosomics was obtained by McGinnis and Campbell (1960). The
frequency obtained in the present study is consistent with those
reported by these workers. However, Joshi et al. (1968) reported a
very high frequency of double monosomics (1.9%) in the selfed
progenies of Chinese Spring monosomic lines. Since the presence of
double monosomics and trisomics may permit univalent shift, a rigid
cytological check of monosomic plants used in selfing or in crossing
programme, is essential, in order to maintain the purity of the
monosomic lines.
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