CSIRO Division of Plant Industry
North Ryde (Sydney) 2113 and Canberra 2600,
Australia.
Program leader Dr. R. Appels.
Wheat germplasm and grain quality program.
This is one of several research programs of the CSIRO Division of Plant Industry, based in Canberra, Australia. Staff of the program are located at both the Grain Quality Research Laboratory, in Sydney, and at the division's headquarters in Canberra, permitting the integrated study of wheat quality at technological, chemical, and genetic levels. The participation of this research program in the recently created Cooperative Research Centre for Quality Wheat
Products and Processes will expand opportunities
for collaboration with other research groups and with the wheat-growing
and processing industries.
An important achievement of the past
year has been the transformation of wheat with the regeneration
of phenotypically normal transgenic plants and also contributions
to the transformation of barley. We recognise the need to identify
the most worthwhile genes to target for application of the technology
(a major goal of our other research), as well as suitable promoter
sequences. Steps towards these goals involve the application
of gene probing. Such studies have involved the development of
new approaches to identify sources of pathogen resistance, new
information about the relatives of wheat, and methods of genotype
identification.
Wheat-grain proteins and dough function.
Our very-small-scale dough
testing equipment is helping breeders to test at an earlier stage
and is an important research tool for identifying the proteins
involved in specific aspects of dough function. Study of the
contributions of specific proteins has included the role of rye
proteins in 1RS lines and study of durum wheats. Beyond the level
of identifying coding genes and specific polypeptides, their polymerisation
into macromolecules has been identified as critical to their functional
properties in dough. New approaches to analysing size distribution
have been developed to further elucidate this relationship.
Direct observation of the contributions
to dough properties of individual polypeptides have been made
in the 2-gram Mixograph, after initially developing a procedure
for breaking and reforming disulfide bonds, in the process of
incorporating added glutenin polypeptides into the macromolecular
structure. The study of individual polypeptides has included
those purified from flour and also proteins expressed heterologously
in bacteria from the isolated gluten genes. These mixing studies
h also ave included elucidation of the role of the `improver',
bromate.
The development of antibodies specific
to particular groups of gluten proteins has provided the opportunity
of identifying amino acid sequences expected to relate to dough-quality
attributes. Such antibodies have been used to provide predictions
of dough strength, to identify the presence of rye protein in
wheat-rye translocation lines, and to identify other alien-chromosome
substitutions.
Molecular studies on starch and grain
hardness.
A starch-granule protein associated
with the soft-grain character in wheat has been further characterised,
and the genes for its synthesis have been cloned. The locus for
this protein has been studied in the wheat progenitor Triticum
tauschii. This species also has been used to study the mechanisms
of starch synthesis.
Wheat-starch
structure is particularly important for noodle-processing
quality, and a predictive system of quality evaluation has been
developed based on chemical analysis. For industrial use of wheat
starch, a high paste viscosity is important. We have shown that
loss of viscosity may be due to the presence of residual FONT SIZE=2 FACE="WP Greek Century""-amylase
after washing.
Modification of grain quality by growth
environment.
Starch and protein quality are affected by growing conditions. In particular, a few days of heat stress can produce an increase in the proportion of large (A-type) starch granules and a weakening of dough properties. On the other hand, modest temperature increases (15 to 35 C) during grain filling appear to cause a strengthening in dough properties. Because genotypes differ in their reactions to temperature change, we have examined a range of wheats for quality changes to identify those that are more tolerant to heat stress. Another approach to overcoming the problems of
quality variation due to environmental
factors is to predict the extent of these variations. We have
focused on the protein content of wheat and barley, for which
winter rainfall and spring heat stress were identified as major
factors.
Quality protection during storage
.
Beyond harvest, the conditions of grain
storage and transport are critical to providing the market with
grain of suitable quality. Moisture content and temperature are
the critical factors taken into account in modeling the rates
of quality change for a range of grains. These models have been
used to develop predictive software to better manage grain storage,
even for rain-damaged grain.
Pesticide treatment is still an important
means of protecting stored grain from insect attack, but there
is a need to monitor treatment to ensure that minimum residue
levels are not exceeded. We have developed antibody-based
test kits to determine the levels of specific pesticides in grain
-
fenitrothion, chlorpyrifos-methyl, bioresmethrin, and several
others. The development of these test systems requires the application
of sophisticated organic chemistry, but the immunoassay principle
is capable of delivering results fast (within 15 minutes) under
field conditions. The tests have been used to determine the fate
of pesticides during milling and baking. Immunoassay systems
also have been developed for agrochemicals used in irrigated agriculture,
particularly for the pesticide endosulfan. The speed and portability
of test kits are already improving the management of irrigation
waters.
Rapid determination of grain quality attributes.
In addition to their use in agrochemical
analysis, antibodies have proved valuable for determining dough
strength, the presence of rye proteins, and varietal identity.
Near-infrared spectroscopy also has been used for grain-quality
testing, originally for moisture and protein analysis. More recently,
we have improved on calibration procedures for these analyses
and extended the capability of this technology towards dough-property
analysis and distinguishing red-grained wheats from white
wheat.
The need to make this distinction arises
from the recent registration of red wheats for growing in Australia
where wheat has exclusively been white grained. Therefore, we
have examined a range of methods for visually distinguishing red
from white wheat with a reflection colour meter or by image analysis.
Image analysis also has been used to identify yellowed grains
in samples of milled rice.
Because genotype is a major indicator
of grain quality for all species, variety is used widely as a
basis for quality segregation, and there is a pressing need for
better methods and strategies for variety identification. Visual
methods are limited. Analysis of protein composition has proved
adequate for many grain varieties, using immunoassay, column chromatography,
and gel electrophoresis. DNA probing methods now are being developed
for the direct identification of genotype for grains.
Annual report available.
Full details of the program's
research results are provided in our publications. The details
of 150 papers, for the year July, 1993, to June, 1994, are given
in our Annual Report, available on request from Colin Wrigley
(Fax: 612 887 8419 or E-mail: c.wrigley@pi.csiro.au).
Queensland Wheat Research Institute
PO Box 2282, Toowoomba Q 4350, Australia.
Wheat breeding.
P.S. Brennan, P.M. Banks, J.A. Sheppard,
and M. Cooper.
The drought that commenced in the summer
of 1990-91
continued throughout 1994, when it was at its most severe. Queensland
produced 180,000 t of wheat in 1994. The long-term average is
1.4 m t. The most recent occasions when Queensland has produced
less wheat than this were in 1970 and 1946. In those years, the
area that could be sown to wheat was less than half of what it
is today.
One set of yield trials was established
and maintained with irrigation, and all others were either not
planted or failed to develop secondary roots. It is clear from
previous experience with such trials that yield prediction is
poor.
For a number of years, we have advocated
the use of BC1F2 populations as the starting
point for a breeding program. The recurrent parent would have
the greater number of favourable alleles. This approach has been
emphasised in the QWRI breeding program for sometime, and late
generation material derived from this type of population has been
evaluated over the last few years.
This material is exhibiting very large
advances for yield, while combining the better quality and disease
resistance attributes of both parents. These results have been
obtained consistently over 2 or more years. This type of outcome
is consistent with the predictions made from theoretical considerations.
We are now using BC1F2-derived populations,
almost exclusively, as the starting point for our wheat breeding
activities in our pedigree program.
The much maligned backcross procedure
has been used to transfer genes for a number of economically important
diseases into adapted cultivars. Two varieties were released
last year from this program. Both varieties exhibited nontarget
improvements of economic importance. This probably was due to
the evaluation of fairly large populations at the BC3
level and to using a number of resistant BC1 lines
as donor parents.
In 1995, we anticipate the release
of two more backcross derived lines. QT5793 is based on Hartog
and has yellow (tan) spot resistance from CNT2. The second is
based on Ford and has mildew and rust resistance from 1BL-1RS.
This will provide a stem, leaf, and stripe rust resistant hay-wheat
for Queensland.
Staff changes. Mr.
Ma Wujun was awarded a PhD scholarship through the University
of Southern Queensland to work on the location of molecular markers
for genes for high protein.
Ms. Tanya Pearce will continue the
development and assessment of wheat/barley translocations for
the transfer of the barley FONT SIZE=2 FACE="WP Greek Century""-amylase
inhibitor from barley to wheat. This work was commenced by Mr.
Ian Haak who has completed writing up the work for a master's
degree. Ian is now involved in a project to locate molecular
markers for a number of disease resistance genes. The disease
resistances selected for this work are effective, but selection
on a single plant basis is difficult because of low heritability.
Double haploids will be used.
Russian wheat aphid. For some time, we have been backcrossing resistance to the Russian wheat aphid into varieties adapted to Australia. This has been accomplished by resistance testing at Colorado State University by Professor Jim
Quick. Agronomically acceptable lines
have been identified in a number of populations and will be yield
and quality tested in the near future.
Mr. Steve Kammholz has developed a
small double-haploid population from a `Turcikum
57/Hartog'
cross. This population segregates in a 1:1 manner, suggesting
a single gene for RWA resistance in Turcikum 57.
Steve Kammholz.
A considerable effort has been committed
to developing double haploids in wheat using pollination with
maize and chromosome doubling with colchicine. The technical
problems associated with the development of haploids were overcome,
and large populations developed. The initial doubling was unsuccessful
because of high glasshouse temperatures. The process was repeated
in 1994 using much cooler conditions and was successful.
This procedure is now routine and is
being applied to a number of research projects.
Funds are being sought to determine
the utility of double haploids in a breeding program.