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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 availability
and their use is available through Steve Reader (steve.reader@jic.ac.uk) of the
Crop Genetics Department of the John Innes Centre..
Aneuploid Stocks ReportAlien Introductions + Miscellaneous Amphiploids ReportIntervarietal 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@jic.ac.uk)