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Wheat Information
Service
Number 74: 1-3 (1992)
Review
A
guide to the wheat aneuploids
Kozo Nishikawa
Gifu University, 1-1, Yanagido, Gifu 501-11, Japan
Thanks to the late Dr. E. R. Sears, the various aneuploid series have
been available in common wheat, which are indispensable for
cytogenetic studies. To avoid confusion, Sears (1975) defined
aneuploids as "individuals with a changed number of chromosomes,
chromosome arms, or centromeres, or with arms so arranged that normal
pairing and disjunction can not occur at meiosis".
1. Types of aneuploids
Monosomics and trisomics were primarily isolated in offspring of
haploid Chinese Spring wheat, from which nullisomics and tetrasomics
were subsequently derived, respectively. General description and
breeding behavior of these complete series of aneuploids and some
other aberrations were summarized by Sears (1954). By means of
several backcrosses of a certain common wheat cultivar to Chinese
Spring monosomics, the monosomics of that cultivar have been
developed. Worland (1988) compiled the catalogue of monosomic series.
Using monosomics, nullisomics and tetrasomic, Sears was successful in
obtaining 42 possible nullisomic-tetrasomic compensating combinations
and several non-compensating ones in variety Chinese Spring, and
reported their origin and characteristics (Sears 1966).
So called secondary aneuploids, telocentrics and isochromosomes are
also available in the variety Chinese Spring. Sears and Sears (1978)
reported telocentrics; their origin, designations, cytological
behavior, fertility, morphology, uses and so on. Representative
monosomics and deletion aneuploids were illustrated in
Figs1 and
2.
Much effort has been successfully devoted to develop the alien
chromosome lines, alien chromosome additions and substitutions.
Shepherd and Islam (1988) compiled the compendium of wheat-alien
chromosome lines.
Various types of aneuploids in tetraploid wheat are also available
(Joppa 1987).
2. Use of aneuploids
Wheat aneuploids have been used not only for genetic analyses but
for developing the new aneuploids. There are several references in
which methods and procedures of using wheat aneuploids in cytogenetic
studies are demonstrated (Sears 1953, 1969, 1972, Kimber and Sears
1980, Law and Snape 1987. McIntosh 1987).
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