GrainGenes

ITEMS FROM AUSTRALIA

 

THE UNIVERSITY OF ADELAIDE

Waite Campus, Plant Science, Glen Osmond, SA 506, Australia.

Research interests. [p. 21]

• Biochemistry and genetic control of factors that cause deterioration of wheat quality prior to harvest (preharvest sprouting and tolerance to preharvest sprouting, grain dormancy, late maturity a-amylase, and black point).
• Biochemical and genetic control of color and color stability in Asian noodles (grain and flour constituents involved in color of wheat flour and color and color stability in Asian noodles; xanthophylls, flavonoids, polyphenol oxidase, peroxidase, lipoxygenase, and nutritive aspects of cereal xanthophylls, lutein and lutein esters).
• Durum germ plasm with tolerance to hostile soils and root diseases and better adaptation to southern Australia.

Preharvest sprouting tolerance in white-grained wheats. [p. 21]

Daryl Mares and Kolumbina Mrva.

Preharvest sprouting periodically causes massive losses to the Australian wheat industry and affects all states, albeit with different frequency. Cultivar improvement via the introgression of dormancy from landraces introduced from South Africa, AUS1408, and more recently from China, SW95-50213, is being undertaken in all Australian breeding programs. The same highly significant QTL on chromosome 4A was associated with dormancy in AUS1408, SW95-50213, and a dormant single gene red genotype, AUS1490, despite their apparent diverse origin. This QTL corresponded with the QTL previously identified in a partially dormant Australian wheat, Halberd, and a number of red-grained wheats. Two SSR markers flanking the highest LRS (Likelihood Ratio Statistic) position on 4A were used to select doubled-haploid lines (dormant / nondormant) containing the dormant parent alleles. The dormancy phenotype of lines in these subpopulations varied from dormant to intermediate. The observations appeared to be consistent with a model in which the 4A QTL is the key component of the dormant phenotype, contributing intermediate dormancy on its own and strong dormancy in combination with 1-2 additional genes. A doubled-haploid population, fixed for the 4A dormancy allele but varying with respect to the additional genes, is being mapped currently.

Late-maturity alpha-amylase in wheat. [p. 21-22]

Kolumbina Mrva and Daryl Mares.

Late-maturity alpha-amylase (LMA) is a genetic defect that can give rise to high grain a-amylase activity, low falling number (typically 200-300 sec but in some instances < 200 sec.), in the absence of sprouting and depending on the environmental conditions during the middle stages of grain filling. The defect is present at low levels in Australian wheat breeding programs and has been identified in genotypes from the U.K., Japan, China, South Africa, Mexico (CIMMYT), and possibly the U.S. (California). Once introduced, the defect is very difficult to eliminate from breeding programs. Preliminary data suggests that LMA is common in synthetic wheats and derived synthetic wheats. A number of sources have been examined and in each case the tendency to produce high alpha-amylase activity was linked to QTL located on 3B and 7B. These QTL appeared to be independently effective and additive. The effects of these QTL were reduced in the presence of semi-dwarfing genes, Rht1 and Rht2, and increased in the presence of 1B/1R.

Current work is focused on populations involving different sources of LMA including an 'Opata/Synthetic' population, the underlying biochemical mechanisms involved, and the temperatures or temperature differential required for maximal expression.

Biochemical and genetic control of color and color stability in Asian noodles. [p. 22]

Robert Asenstorfer, Richard Leach, Imelda Soriano, and Daryl Mares.

Our aims are to identify and quantify the biochemical constituents, enzymes and interactions that influence quality, specifically color, and. hence. marketability of noodles; develop efficient, small-scale screening technologies for color and color constituents; identify QTL/genes associated with control of color components; develop and validate molecular markers for critical traits; and exploit available genetic variation, mutations, and synthetic wheats to develop wheat genotypes with improved or novel characteristics.

Polyphenol oxidase (PPO). Australian cultivars vary from high (unacceptable for alkaline noodles due to excessive darkening) to low in benchmark cultivars such as Sunco. Recently, a bread wheat genotype with PPO levels significantly less than Sunco and synthetic derived material with zero PPO have been identified. This material provides incremental improvements in color stability (i.e., reduced rate of darkening). In the absence of PPO, there is still significant darkening contributed by non-PPO enzymic activity. QTL associated with variation in PPO activity are located on chromosomes 2A and 2D. Current work on this trait includes introgression of very low PPO and zero PPO into locally adapted cultivars and biochemical analysis of the non-PPO component.

Flavonoids. Water and 0.1 M hydroxylamine extract compounds from whole meal or flour that are colorless at neutral pH but which turn yellow at higher pH (e.g., as in yellow alkaline noodles, YAN). The germ tissues contain free and phenolic esters of apigenin-C-diglycosides that contribute to the total yellow color of YAN. whereas the seed coat or bran contains nonflavonoid phenolics that have a minor role. The proportion of total flavonoid that is recovered in flour during milling appears to vary with both genotype and plant growth environment.

Lipoxygenase. Variation in both the 'Sunco/Tasman' and 'Opata/Synthetic' populations was associated with a QTL on chromosome 4B located close to the centromere and in the case of the 'Sunco/Tasman' population, Rht1.

Durum germ plasm with better adaptation to southern Australia. [p. 22]

David Cooper and Daryl Mares.

Durum production in the southern region of Australia expanded rapidly in the late 1990s but more recently has declined in popularity in the face of inconsistent performance and perceived deficiencies in adaptation to the local environment. This new project began in 2004 and aims to introgress tolerance to a range of hostile soil (boron toxicity, salinity, high bicarbonate, and zinc deficiency), disease (crown rot and nematodes), and grain defects (sprouting, high alpha-amylase, and black point) traits into elite durum genotypes. Part of the research will also be directed at improving semolina yellowness.

Publications.

• Asenstorfer RE, Wang Y, and Mares DJ. 2004. Yellow colour in alkaline noodles. In: Cereals 2004, Proc 53rd Aus Cereal Chem Conf (Black CK, Panozzo JF, and Rebetzke GJ, Eds). Pp. 175-178.
• Leach RC and Mares DJ. 2004. Quantitative trait locus associated with lipoxygenase activity in bread wheats: a tool to improve the marketability of Australian bread wheat. In: Cereals 2004, Proc 53rd Aus Cereal Chem Conf (Black CK, Panozzo JF, and Rebetzke GJ, Eds). Pp 130-133.
• Mares DJ, Mrva K, Cheong J, Williams KJ, Cavallaro B, Storlie E, Sutherland M, and Zou Y. 2004. Genetic control of dormancy in white-grained wheats of diverse origin. In: Cereals 2004, Proc 53rd Aus Cereal Chem Conf (Black CK, Panozzo JF, and Rebetzke GJ, Eds). Pp. 231-233.
• Mares DJ, Mrva K, and Fincher GB. 2004. Enzyme activities. Encyclopedia of Grain Science (Wrigley C, Corke H, and Walker C, Eds). Elsevier Science, London, UK. 1:357-365.
• Mares DJ and Campbell AW. 2001. Mapping components of flour and noodle colour in Australian wheat. Aus J Agric Res 52:1297-1309.
• Mrva K, Mares DJ, Williams KJ, and Cheong J. 2004. Molecular markers associated with late maturity a-amylase (LMA) in wheat. In: Cereals 2004, Proc 53rd Aus Cereal Chem Conf (Black CK, Panozzo JF, and Rebetzke GJ, Eds). Pp 150-151.