Soil salinity and sodicity are major constraints to global cereal production, but breeding for tolerance has been slow. Narrow gene pools, over-emphasis on the sodium (Na+) exclusion mechanism, little attention to osmotic stress/tissue tolerance mechanism(s) in which accumulation of inorganic ions such as Na+ is implicated, and lack of a suitable screening method have impaired progress. The aims of this study were to discover novel genes for Na+ accumulation using genome-wide association studies, compare growth responses to salinity and sodicity in low-Na+ bread Westonia with Nax1 and Nax2 genes and high-Na+ bread wheat Baart-46, and evaluate growth responses to salinity and sodicity in bread wheats with varying leaf Na+ concentrations. The novel high-Na+ bread wheat germplasm, MW#293, had higher grain yield under salinity and sodicity, in absolute and relative terms, than the other bread wheat entries tested. Genes associated with high Na+ accumulation in bread wheat were identified, which may be involved in tissue tolerance/osmotic adjustment. As most modern bread wheats are efficient at excluding Na+, further reduction in plant Na+ is unlikely to provide agronomic benefit. The salinity and sodicity tolerant germplasm MW#293 provides an opportunity for the development of future salinity/sodicity tolerant bread wheat.

Darkening in yellow alkaline noodles (YAN) was examined over a 24 h period in noodles made from 4 wheat varieties, including varieties with different levels of polyphenol oxidase (PPO) activity, selected to cover a range of protein levels. Noodles were made in the presence and absence of the PPO inhibitor, tropolone. The darkening was divided into two time periods: 0-4 h and 4-24 h. The first four hours was described by a composite rate equation, and this period was subdivided into two stages. The rate of darkening in the first stage was independent of both protein concentration and PPO activity. The amount of darkening (c), however, was highly dependent on protein concentration during this stage (-tropolone, r = 0.902; +tropolone, r = 0.905), but independent of PPO activity. The first stage darkening was a zero order reaction where additional protein does not increase the reaction rate, but when the protein supply has been depleted, the reaction stops. The rate of darkening during the first stage (k'(1) = 5.6 +/- 1.0) was similar to the rate of change in the protein structure (k'(1) = 6.5 +/- 1.3) as measured using the amide II band by infrared spectroscopy. This suggested that the first stage of darkening represents changes in light reflectance and absorbance caused by changes in hydrogen bonding rather than changes in covalent bonding. During the second stage of darkening, both the rate (k'(2)) and amount of darkening (DeltaL*(4h-c)) were significantly correlated with protein concentration (-tropolone, r = 0.465; +tropolone, r = 0.813), and in the absence of tropolone the amount of darkening was increased by PPO activity. The amount of darkening (DeltaL*(24h-4h)) during the second time period (4-24 h) (or third stage) was significantly correlated in the presence of tropolone (r = 0.375) and in the absence of tropolone (r = 0.428) with protein concentration. However, compared with earlier stages the response of non-PPO darkening during the third stage to change in protein concentration was smaller. Protein oxidation, or more specifically oxidation of tyrosine groups within the protein, appears to be the main mechanism involved in non-PPO darkening in YAN during the second and third stages with glutenin being the main reactant. Albumin and globulin are important substrates for PPO. No differences in darkening were detected in YAN made from the four varieties in the presence of tropolone; however, differences in YAN darkening were observed for the second and third stages due to site and year variation.

Darkening in yellow alkaline noodles (YAN) was measured over 24 h in a high polyphenol oxidase (PPO) bread wheat ( Triticum aestivum L. cv. Tasman) and a very low PPO durum wheat ( Triticum durum cv. Kamilaroi). Over 24 h non-PPO darkening occurred across a range of pH 3.5-10.5, and in Tasman this was overlaid by darkening from PPO activity. The rate of darkening in YAN was separated into two main time periods, 0-4 and 4-24 h. The first 4 h of darkening was further divided into two stages using a composite first-order rate equation. Several specific inhibitors that partially inhibited non-PPO darkening were identified. These inhibitors, as well as the PPO inhibitors SHAM and tropolone, were used to analyze YAN darkening. The rate of the early stage of darkening was not altered by any inhibitors used; however, the magnitude of darkening was reduced by inhibitors specific for non-PPO darkening. Both the rate and extent of non-PPO darkening of the second stage of darkening were decreased in Tasman and Kamilaroi by inhibitors specific for non-PPO darkening, whereas both PPO inhibitors only decreased darkening in Tasman. The second and third stages of darkening showed similar characteristics. The third stage of darkening was examined in YAN made from Kamilaroi over a temperature range from -4 to 65 degrees C. It followed an Arrhenius relationship indicating non-PPO darkening during this stage was nonenzymatic. The inhibitor data suggested that the reactive component(s) was/were present in a reasonably high concentration(s) and that the soluble protein fraction was involved in the non-PPO darkening process.

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Triticale is a hardy, high yielding cereal crop with a reputation for poor gluten strength. The secalogluten formation capacity was investigated in 17 modern triticale cultivars by defining their HMW glutenin and 75K γ-secalin alleles and then assessing SDS-sedimentation height and mixograph parameters in a subset of cultivars. The allelic diversity was poor with only 13 alleles identified at four loci; nevertheless, sufficient variability existed to allow secalogluten improvement through crossbreeding and selection. SDS-sedimentation height of triticale (35.5 mm) and mixing time (2.7 min) was equivalent to soft wheat but significantly less than hard wheat. However, flour protein content was 16% less in triticale compared to wheat, despite similar grain protein contents, suggesting triticale stores a lower proportion of grain protein in the endosperm. The confounding factor of protein content must be considered as part of an equitable analysis of gluten quality in cultivar breeding, in the interpretation of previous triticale research, and when comparing triticale to wheat. Improved glutenin properties will expand the utility of triticale in human food products and, thus, increase potential profitability.