Postdoc: CSIRO, Plant Industry on "A multilocus linkage group phylogeny of Citrus".

Randall Bayer randy.bayer at CSIRO.AU
Wed Aug 17 00:57:10 CDT 2005

We are seeking candidates to apply to work on the following project:

Title: A multilocus linkage group phylogeny of Citrus (Rutaceae:

Project Background:  The Citrus industry is one of the largest
horticultural industries in the world and the breeding of new, high quality
Citrus cultivars for the industry depends on reliable information about the
relationships among the cultivated and wild Citrus species. Wild Citrus
species are of interest to Citrus breeders as they possess genes that may
provide a number of beneficial traits (e.g., disease resistance and new
fruit characteristics).  Although, Citrus fruits are the most widely
cultivated tree fruit in the world, the evolutionary origins of many of the
commercial classes of cultivars, i.e. lemons, oranges, limes, grapefruits,
are unknown.  As a consequence it has been exceedingly difficult to produce
new cultivars by traditional hybridization/selection techniques, and it is
therefore important to understand the relationships among the different
species of the tribe for advancing breeding techniques and developing
better conservation strategies for wild germplasm.  Our current
understanding of the group suggest that few of the cultivated species are
true biological species [e.g., C. maxima (pummelo), C. medica (citron) and
C. reticulata (mandarin / tangerine)], while many of the more widely known
Citrus types [e.g., sweet oranges (C. sinensis), grapefruits (C. paradisi),
lemons (C. limon), sour oranges (C. aurantium) and limes (C. aurantifolia)]
are fixed hybrid biotypes derived from the “true” species that are
maintained by vegetative reproduction. The chimeric nature of these hybrid
Citrus genomes makes it impossible to apply standard phylogenetic
strategies for determining historical genetic relationships.

Proposed Research:  We propose to produce phylogenies based on sequences
representing each arm of the nine chromosomes in the Citrus genome.  The
resulting phylogenies will help us determine the phylogenetic origin of
each of the chromosomes arms of the of the various cultivar groups.  From
this information we will be able to establish the origin of each linkage
group in each of the cultivar groups, i.e., oranges, grapefruits, lemons,
and limes.  Rudimentary genetic linkage maps exist for Citrus.  To date, 19
linkage maps have been constructed from a series of ten studies.  These
maps will form the basis for selecting appropriate sequences from each
linkage group for sequencing and phylogenetic reconstruction.

Tenure: 3 years

Salary: $58K to $64K (Australian dollars)

Eligibility:  International applicants welcome.  To be eligible for a
Postdoctoral Fellowship you will have received your Ph.D. after the 1st Jan

Closing Date for Application: 1 September 2005

For more information on application procedures contact: Dr. Randall Bayer,
CSIRO, Plant Industry, Canberra, Australia.  randy.bayer at

Web link:

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