Latest Update: 10nd January 2007
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A database of information relating to wheat precise genetic stocks developed and maintained within the Crop Genetic Department of the John Innes Centre is being developed. The aim of the database is to collate information on stock parentage, cytogenetic descriptions and notable phenotypic traits associated with the stocks. The database is presently populated with data relating to some 3000+ stocks. The database is currently managed off-line and reports are generated which details stocks available. These are available for viewing, printing or saving as word documents as listed below. Discussions are underway to develop a web searchable interface to the database.
Advice on stock avaiability and their use is available through Steve Reader (steve.reader@bbsrc.ac.uk) of the Crop Genetics Department of the John Innes Centre..
Aneuploid Stocks Report Alien Introductions + Miscellaneous Amphiploids Report Intervarietal Substitutions Report
Aneuploid stocks
Wheat has an allopolyploid origin, and the homoeology existing between its
three component genomes allows a range of aneuploidy to be tolerated. The late
Prof. Ernie Sears began accumulating this aneuploid set in the 1940's, and it
now comprises around 220 lines. The set is primarily derived from a single
cultivar, 'Chinese Spring', and features the loss of one chromosome (monosomy)
or a pair (nullisomy), extra chromosomes (trisomy and tetrasomy) and
compensation (nullisomy-tetrasomy) involving all 21 constituent chromosomes.
There are also telosomic sets in which the same half of a pair of chromosomes is
missing (derived via centromere breakage of univalent chromosomes during
meiosis. Because each accession has an aneuploid genotype, it is necessary to
screen cytologically at either mitosis and/or meiosis each time they are grown.
The transfer of aneuploidy to agronomically adapted cultivars via traditional
plant breeding methods permitted its effects to be more easily determined.
Similarly, locating genes conferring agronomically important traits became
possible, an obvious example being the mlo locus, which provided an effective
resistance to powdery mildew for many years. With the advent of molecular marker
analysis in the early 1980's, the use of these wheat aneuploids, together with
the wheat/alien aneuploids (see section 2), confirmed that homoeology within the
Triticeae extended beyond the phenotype to the molecular level. This led to the
comparative mapping of wheat and its near relatives, and the construction of a
molecular map of wheat. In this latter exercise, the compensating
nullisomic-tetrasomic lines and telosomic lines have featured prominently.
Alien Introductions
Wheat has an allopolyploid origin, and the homoeology existing between its
three component genomes allows a range of aneuploidy to be tolerated.
Innumerable worldwide research projects spanning more than 60 years has led to
the establishment of this set of wheat/alien aneuploids. Because each accession
has an aneuploid genotype, it is necessary to screen cytologically at either
mitosis and/or meiosis each time they are regenerated. Initially, research
workers employed traditional plant breeding methods to add a pair of chromosomes
from a close relative (alien) to the wheat complement. The establishment of
monosomic series in various wheat cultivars (see the 'Aneuploid' section of
WPGS) then facilitated the substitution of this alien pair for a homoeologous
pair belonging to the wheat. As this unique collection grew, co-operative
studies determined both the induced effects of the aneuploidy, and the
chromosomal location of alien genes conferring agronomically important traits
such as improved disease resistance or tolerance of abiotic stress. One such
example is the 1B.1R translocation so popular in European cultivars in the 1980s
and '90s. With the advent of novel molecular marker analysis in the early
1980's, extensive use of these wheat/alien aneuploids confirmed that the
homoeology within the Triticeae extended beyond the phenotype to the molecular
level.
Intervarietal substitutions
While much of the early work on aneuploidy in wheat was conducted in
'Chinese Spring', many other background varieties have been used. The stocks
developed by Colin Law and the late Tony Worland are currently in the process of
being prepared for inclusion in the database.
References
Law CN, Snape JW, Worland AJ. (1987). Aneuploidy in wheat and its uses in
genetic analysis In: Lupton, F. G. H. (ed.). Wheat Breeding. Its Scientific
Basis, 71-127, Chapman and Hall, London and New York.
Page maintained by M.J.Ambrose Genetic Resources Unit Manager (mike.ambrose@BBSRC.AC.UK)