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Phenotypic plasticity is the ability of an individual genotype to express phenotype variably in different environments. This study investigated the plasticity of yield-related traits of bread wheat by utilising 225 doubled haploid (DH) lines developed from cv. Westonia and cv. Kauz, through two field trials in Western Australia. Plasticity was quantified via two previously published methods: responsiveness to varying ecological conditions and slopes of reaction norms. The spikelets/spike was the most plastic trait, with an overall plasticity of 1.62. The least plastic trait was grain protein content, with an overall plasticity of 0.79. The trait hierarchy based on phenotypic plasticity was spikelets/spike > thousand kernel weight > seed number > seed length > grain yield > grain protein content. An increase in yield plasticity of 0.1 was associated with an increase in maximum yield of 4.45 kg ha−1. The plasticity of seed number and grain protein content were significantly associated with yield plasticity. The maximal yield was positively associated with spikelets/spike and grain yield, whereas it negatively associated with grain protein content. In contrast, the minimal yield was found to be negatively related to the plasticity of spikelets/spike and the plasticity of grain yield, whereas it was not related to grain protein content plasticity. Seed number and seed length exhibited plastic responses at the higher fertilisation state while remaining relatively stable at the lower fertilisation state for the wheat DH population. The finding of the current study will play a key role in wheat improvement under the changing climate. Seed length and seed number should be the breeding target for achieving stable yield in adverse environmental conditions. [ABSTRACT FROM AUTHOR]

Water availability is the most important aspect of plant growth and development, which has an impact on crop yield and productivity. Plants respond to water shortages by altering their physiology, biochemistry, and osmotic balance. This study aimed to evaluate the role of K applications on wheat performance under water stress. The study was comprised of five levels of potassium applications, i) NK = control-no K applied, ii) WA = water applications at the heading stage (50 DAS), iii) K50 = 50 mg L-1, iv) K100= 100 mg L-1, and v) K150 = 150 mg L-1, and two levels of water status viz. i) WS0 = Control-no Water stress and ii) WS1 = Water stress (50 DAS). Results revealed that plant height, leaf area, and dry weights were decreased by 29.3, 20.8 and 23.3%, respectively, under water stress due to the reduction in the photosynthetic pigments in plants. Alternatively, cell membrane injuries were increased along with the overproduction of malondialdehyde and hydrogen peroxide. However, the production of metabolites (soluble proteins and phenolics), and antioxidant enzymes (superoxide dismutase, catalase, protease, and peroxidase) regulate plant defense. The K supplementation ameliorated the harmful effect of water stress as proved by improving plant growth attributes, leaf area and dry weight, and chlorophyll contents. In addition, the production of antioxidant enzymes and metabolites contents were increased under K applications which improved stomatal conductance and photosynthetic rate by 38.4 and 12.8%, respectively resulting in the grain yield increase of 25.3%. Among the different K levels, K applied at 150 mg L-1 was the most effective as compared to 50 mg L-1 and 100 mg L-1, which increased the seed yield by 29.5% as compared to the control. In crux, K applications have an important role to impart water stress tolerance in wheat plants based on the improvements in plant physicochemical activities. [ABSTRACT FROM AUTHOR]

Wild emmer, the direct progenitor of modern durum and bread wheat, has mostly been studied for grain quality, biotic, and abiotic stress-related traits. Accordingly, it should also have a certain amount of diversity for morphological and agronomic traits. Despite having a high chance of huge diversity, it has not been deeply explored. In the current study, 263 wild emmer accessions collected from different regions of Israel, Turkey, Lebanon, and Syria were characterized for a total of 19 agronomic and shoot morphological traits. Three trials were carried out in Western Australia, which demonstrated a large variation in these traits. The average phenotypic diversity (H') was 0.91 as quantified by Shannon's diversity index. A high heritability was recorded for most of the traits, where biomass/plant and yield/plant were identified as the most potential traits. Correlation analysis revealed several significant associations between traits, including significant positive correlation between yield and tiller number, first leaf area, spike length, and biomass/plant. The principal component analysis (PCA) demonstrated that most of the traits contributed to the overall observed variability. The cluster analysis categorized 263 accessions into five clusters on average. On the other hand, accessions were categorized into eight populations based on the collection region and a comparative analysis demonstrated considerable variations between populations for plant height, spike length, and flag leaf area. Despite the low yield, several wild emmer accessions demonstrated superior performance compared to modern bread wheat cultivars, when selection was based on combining yield with multiple traits. These observations indicate that wild emmer contains a broad gene pool for several agronomic and shoot morphological traits, which can be utilized for bread and durum wheat improvement. [ABSTRACT FROM AUTHOR]

A doubled haploid mapping population was developed from a cross between the hard red winter wheat (Triticum aestivum L. subsp. aestivum) landrace PI 173438 and WA 8137, a soft white winter wheat breeding line developed by the Washington State University winter wheat breeding program in Pullman, WA. The PI 173438/WA 8137 (Reg. no. MP‐16, NSL 543858 MAP) population consists of 437 individuals, with 358 of these individuals used to identify quantitative trait loci associated with snow mold (Typhula spp.) tolerance in PI 173438. Genotypic information was gathered on these individuals using genotype‐by‐sequencing and processed using a pipeline developed by the USDA Eastern Regional Small Grains Genotyping Laboratory. Twenty‐three linkage groups covering the whole genome with groups for the long and short arms of chromosomes 3D and 7D were constructed using 4,029 single nucleotide polymorphisms from the sequenced individuals. Quantitative trait loci associated with snow mold tolerance and snow mold recovery attributed to PI 173438 were successfully identified in this population. PI 173438 has also been used to identify other traits associated with snow mold tolerance, such as freezing tolerance and carbohydrate reserves, and has been important in research investigating dwarf and common bunt. This population may continue to expand current knowledge in these areas, and, given the landrace status of PI 173438, the population may be useful in identifying other novel traits of interest. Core Ideas: Landraces remain vital sources of genetic diversity for trait improvement.The PI 173438/WA 8137 population can aid in research of novel genetics.Snow mold tolerance QTL have been identified in the PI 173438/WA 8137 population. [ABSTRACT FROM AUTHOR]

Rotations and associated management practices in rainfed farming systems of southwest Australia have shifted towards intensified cropping. Survey data from 184 fields spanning 14 Mha of southwest Australia were used to document water use efficiency (WUE) and water-limited yield potential (WLYP) of commercial crops and crop sequences and identify biophysical variables influencing WUE. WUE achieved in commercial wheat crops was 10.7 kg grain/ha.mm. Using a boundary function Ywl = 25 × (WU − 45), farmers achieved 54% of WLYP. Climate variables affected WUE more than management and biotic variates, the highest latitude region having WUE of 9.0 kg grain/ha.mm, compared to 11.8 kg grain/ha.mm for regions further south. Increased soil nitrogen and nitrogen fertiliser increased WUE, as did sowing earlier; in keeping with farmers in southern Australia sowing crops earlier and trebling fertiliser nitrogen usage since 1990. Wheat yield and WUE increased a small amount after break crop or pasture (12.5 kg grain/ha.mm) compared to wheat grown after wheat (11.2 kg grain/ha.mm), due to good weed and root pathogen control, and high fertiliser nitrogen application. However, WUE of wheat declined to 8.4 kg grain/ha.mm when more than three wheat crops were grown in succession. Farmers continue to improve WUE with increased inputs and new technologies replacing some traditional functions of break crops and pasture. However, break crops and pastures are still required within the rotation to maintain WUE and break effects need to be measured over several years. High water use efficiency was associated with low levels of weed, disease and high fertliser nitrogen inputs in Western Australia's rainfed cropping systems. The yield benefit to wheat sown immediately after break crops or pasture was low, because of low levels of biophysical constraints. However, water use efficiency of wheat declined when three wheat crops were grown in succession. This highlights the need for continued research into the integration of break crops and pastures into wheat dominated rotations. [ABSTRACT FROM AUTHOR]

In areas of the Pacific Northwest (PNW), snow mold, a fungal disease with multiple causal agents, can have severe impacts on winter wheat (Triticum aestivum L. subsp. aestivum) yields. Growing tolerant varieties is the best option to manage the disease; however, genetic diversity for the trait is limited in local varieties. The winter wheat landrace PI 173438 has been used in Japan to improve snow mold tolerance but has not been used in PNW breeding programs. A doubled haploid population from a cross between PI 173438 and susceptible variety WA 8137 was used to identify novel quantitative trait loci (QTL) associated with snow mold tolerance that would be validated using marker‐assisted selection (MAS) in two separate populations. A linkage map was developed using genotypic data collected on the PI 173438/WA 8137 population, which was then used with phenotypic data in composite interval mapping for QTL analysis. Six QTL were found associated with snow mold tolerance traits, five of which originated from PI 173438. A QTL was found on chromosome 1D that has not been reported before. The remaining QTL occurred on chromosomes that were previously reported to have snow mold tolerant QTL, some of which may be identical. Several of these QTL and linked markers were suitable for testing via MAS on separate populations revealing no significant difference amongst the three or four QTL that could be tested. Such results continue to indicate the complexity of breeding for snow mold tolerance using molecular markers. Core Ideas: PI 173438 was found to possess novel QTL associated with snow mold tolerance.Complexity in snow mold tolerance contributed to challenges in validating the QTL.Marker‐assisted selection is still difficult to use in wheat on quantitative traits like snow mold tolerance. [ABSTRACT FROM AUTHOR]

Unknown genetic architecture makes it difficult to characterize the genetic basis of traits and associated molecular markers because of the complexity of small effect quantitative trait loci (QTLs), environmental effects, and difficulty in phenotyping. Seedling emergence of wheat (Triticum aestivum L.) from deep planting, has a poorly understood genetic architecture, is a vital factor affecting stand establishment and grain yield, and is historically correlated with coleoptile length. This study aimed to dissect the genetic architecture of seedling emergence while accounting for correlated traits using one multi-trait genome-wide association study (MT-GWAS) model and three single-trait GWAS (ST-GWAS) models. The ST-GWAS models included one single-locus model [mixed-linear model (MLM)] and two multi-locus models [fixed and random model circulating probability unification (FarmCPU) and Bayesian information and linkage-disequilibrium iteratively nested keyway (BLINK)]. We conducted GWAS using two populations. The first population consisted of 473 varieties from a diverse association mapping panel phenotyped from 2015 to 2019. The second population consisted of 279 breeding lines phenotyped in 2015 in Lind, WA, with 40,368 markers. We also compared the inclusion of coleoptile length and markers associated with reduced height as covariates in our ST-GWAS models. ST-GWAS found 107 significant markers across 19 chromosomes, while MT-GWAS found 82 significant markers across 14 chromosomes. The FarmCPU and BLINK models, including covariates, were able to identify many small effect markers while identifying large effect markers on chromosome 5A. By using multi-locus model breeding, programs can uncover the complex nature of traits to help identify candidate genes and the underlying architecture of a trait, such as seedling emergence. [ABSTRACT FROM AUTHOR]

Septoria nodorum blotch (SNB) is a necrotrophic disease of wheat prominent in some parts of the world, including Western Australia (WA) causing significant losses in grain yield. The genetic mechanisms for resistance are complex involving multiple quantitative trait loci. In order to decipher comparable or independent regulation, this study identified the genetic control for glume compared to foliar resistance across four environments in WA against 37 different isolates. High proportion of the phenotypic variation across environments was contributed by genotype (84.0% for glume response and 82.7% for foliar response) with genotype-by-environment interactions accounting for a proportion of the variation for both glume and foliar response (14.7 and 16.2%, respectively). Despite high phenotypic correlation across environments, most of the eight and 14 QTL detected for glume and foliar resistance using genome wide association analysis (GWAS), respectively, were identified as environment-specific. QTL for glume and foliar resistance neither co-located nor were in LD in any particular environment indicating autonomous genetic mechanisms control SNB response in adult plants, regulated by independent biological mechanisms and influenced by significant genotype-by- environment interactions. Known Snn and Tsn loci and QTL were compared with 22 environment-specific QTL. None of the eight QTL for glume or the 14 for foliar response were co-located or in linkage disequilibrium with Snn and only one foliar QTL was in LD with Tsn loci on the physical map. Therefore, glume and foliar response to SNB in wheat is regulated by multiple environment-specific loci which function independently, with limited influence of known NE- Snn interactions for disease progression in Western Australian environments. Breeding for stable resistance would consequently rely on recurrent phenotypic selection to capture and retain favorable alleles for both glume and foliar resistance relevant to a particular environment. [ABSTRACT FROM AUTHOR]

Cultivar disease resistance ratings to nodorum blotch (caused by Parastagonospora nodorum) provide critical information to growers to assist with disease management. However, less has been done in terms of yield losses from diseases under different cultivar resistance scenarios. The purpose of this study was to characterize yield and quality loss responses to wheat nodorum blotch as influenced by variety partial resistance, epidemic intensity, and environment. The trial series includes four site/years in Western Australia. Five varieties, Magenta, Calingiri, Trojan, Janz, and Scout were used for all four trials. These varieties represented resistant/susceptible categories MRMS, MS, MSS, S, and SVS, respectively, and were selected on the basis that they were adapted to the western region, had similar maturities, and were resistant to diseases that were potential contaminants. Trials were sown in a strip‐plot design with three replicates and five disease levels, with intersecting main‐plots of varieties and disease levels, which facilitated comparisons across disease levels within varieties. Current categories of resistance were well reflected in yield and quality responses. A negative exponential relationship was observed between yield and disease, with a nonlinear yield loss function for both flag leaf and glume infection. This indicates that yield is most affected during early stages of disease on flag leaves and glumes. The functional form of yield loss response over four site years was similar among varieties, but varieties differed in their extent of disease expression. Partial resistance in commercial wheat varieties reduced yield loss by 40%–60% of losses observed in susceptible varieties. [ABSTRACT FROM AUTHOR]

Processing quality of winter-wheat is affected by genotype, environmental conditions, and crop husbandry practices. In the present study, a data set of 17 quality-related traits for 211 main winter-wheat varieties in China during 2006 to 2018 was extracted from China Wheat Quality Report. Analysis was carried out to evaluate the quality status and variations, to reveal correlation between quality-related traits, as well as to identify key influencing factors. Results indicated that the quality indicators of medium-gluten or medium-strong-gluten wheat varieties were acceptable, whereas those of weak- and strong-gluten wheat varieties were far below national standard, especially hardness index (HI), crude protein content (CPC), wet gluten content (WG), and water absorption for weak-gluten wheat and sedimentation value (SV), stability time (ST), and stretch area (SA) for strong-gluten wheat, respectively. Correlation analysis showed that WA, WG, development time, HI, CPC, falling number, ST, and tractility directly affected the overall quality of winter-wheat. CPC, SV, and WG in medium-gluten wheat had no significant correlation with the processing quality of noodles score, whereas gluten index significantly correlated with noodle score (P < 0.001). This implied that protein quality might play a more important role than protein quantity in determining medium-gluten wheat quality. Furthermore, analysis of variance showed that genetic characteristics (cultivars) had significant influences on the restriction indexes (SV, ST, and SA) of strong-gluten wheat, whereas genetic characteristics, environment conditions, and crop growing practices (cultivars, locations, and years) significantly affected the restriction indexes (HI, CPC, WG, and WA) of weak-gluten wheat. The results suggest that improvement of Chinese strong-gluten wheat should mainly focus on cultivating new varieties. As to weak-gluten wheat, cultivation and husbandry practices should be paid more attention to limit undesired high grain protein content. [ABSTRACT FROM AUTHOR]

Development of integrated weed management strategies is dependent on a thorough knowledge of the demography of individual species. The current research established eight winter or summer weed species in a winter annual wheat cropping system at Wongan Hills, Western Australia, and investigated emergence of the first cohort of each species, survivorship, plant size, seed production and seed shedding over three years (2016–2019). The winter weeds Bromus diandrus and Lolium rigidum emerged at the same time as the wheat crop, and the initial cohort of marked plants had 100% survival to seed production in each year. By comparison, other winter weed species like Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus and Polygonum aviculare frequently emerged later than the crop and had a lower percentage of plants surviving to seed production. However, individual S. oleraceus and P. aviculare plants had the greatest seed production compared to other species. All winter weeds had variable patterns of seed shedding between years, with the exception of L. rigidum. Summer weed species emerged at the same time, but plants in the initial cohort of each species did not always survive to produce seed. The early emergence and high survivorship of B. diandrus indicates high competitive ability, but shedding commenced at a similar time to L. rigidum and harvest weed seed control may be a viable control method for this species. [ABSTRACT FROM AUTHOR]

Camelina [ Camelina sativa (L.) Crantz] of the Brassicaceae family is a potential alternative and oilseed biofuel crop for wheat (Triticum aestivum L.)-based cropping systems of the Inland Pacific Northwest (PNW) of the United States. We investigated the effect of this relatively new rotational crop on soil microbial communities. An 8-year cropping systems experiment was initiated in 2007 at Lind, WA, to compare a 3-year rotation of winter wheat (WW)-camelina (C)-fallow (F) to the typical 2-year WW-F rotation. All phases of both rotations (total = 20 plots) were present every year to allow valid statistical analysis and data interpretations. Monoculture WW-F is the dominant system practiced by the vast majority of farmers on 1.56 million ha of cropland in the PNW drylands that receive <300 mm average annual precipitation. Microbial abundance and community composition were determined using phospholipid fatty acid analysis (PLFA) from soil samples collected during 3 consecutive years beginning in 2010. The abundance of fungi, mycorrhizae, Gram positive and negative bacteria, and total microbial abundance all declined over the 3-year period in the WW-C-F rotation compared to the WW-F rotation. All microbial lipid biomarkers were significantly less in fallow compared to WW of the WW-C-F rotation. The 2-year WW-F rotation demonstrated few differences in microbial lipid abundance and community structure between the rotation phases. Microbial abundance declined and community structure shifted in the 3-year WW-C-F rotation likely due to the combination of a Brassica crop followed by a 13-month-long fallow. The results of this study suggest that camelina in combination with a fallow period may disrupt microbial communities that have become stable under historical WW-F monocropping. Such disturbances have the potential to affect soil processes that have been provided by wheat-adapted microbial communities. However, the disruption appears to be short-lived with the microbial abundance of WW in the WW-C-F rotation, returning to similar levels observed in the WW-F rotation. [ABSTRACT FROM AUTHOR]

Pratylenchus curvicauda, which was first described in metropolitan Perth in 1991, was recently identified in grain‐growing areas in Western Australia. The biology of this root‐lesion nematode, and especially its pest status, is unknown. We investigated its life cycle and interaction with host plants, because such information is essential for its management. The life cycle took 45 days to complete in a wheat cultivar maintained at 23°C. Over 10 weeks, the nematode multiplied in 26 of 61 genotypes; these host plants were all cereals and included widely grown cultivars of wheat and barley. Eighteen other cereal genotypes and 13 cultivars including canola, chickpea, ryegrass, lupin, soybean, and tomato, sustained the nematodes to different degrees without multiplication. Four cover crops were not suitable hosts. The patterns of attraction of the nematodes and penetration into roots of the host and tolerant plants were similar. The nonhosts attracted fewer nematodes, none of which penetrated the roots. Browning of infected roots was atypical—it occurred late in some roots, 55 days after inoculation, and in the presence of a fungus. The nematodes were confined to, and fed from, cortical cells. The ultrastructure of infected wheat and barley cells showed typical signs of damage caused by Pratylenchus spp. and included cell disorganization and lack of membrane integrity, disintegration of cytoplasm, hypertrophy of some nuclei, and deposition of tannin‐like granules. This detailed characterization of P. curvicauda–host interaction indicates the nematode is likely to be a pest of major crops, and attention should be given to its management. [ABSTRACT FROM AUTHOR]

Weed seeds are introduced to agronomic systems naturally or through human‐mediated seed dispersal, and introduced seeds have a high chance of being resistant to selective, in‐crop herbicides. However, colonisation (invasion) rates for a weed species are usually much lower than rates of seed dispersal. The current research investigated colonisation of a winter annual wheat cropping system in Western Australia by a range of winter or summer annual weed species. The weed seeds were sown (at 100 seeds/m2) directly before seeding the crop in 2016 and allowed to grow in the following 3 years of wheat. Selective herbicides were not applied, to simulate growth of weed populations if the initial seed had been resistant to herbicide. Bromus diandrus, Hordeum leporinum, Rumex hypogaeus, Sonchus oleraceus, Polygonum aviculare, Lolium rigidum, Citrullus amarus and Tribulus terrestris colonised the crop, while Dactyloctenium radulans, Chloris truncata and Salsola australis failed to establish over 3 years. The most successful weed was B. diandrus, with a plant density of 1,170/m2 by the third year and seed production of 67,740/m2. The high density of B. diandrus reduced wheat density by 76% in the third year and reduced average yield by 36%. Lolium rigidum reduced average yield by 11%, and the other weed species did not affect crop yield. Further research is required on the invasiveness of these species in other regions, but it is clear that the spread of B. diandrus to new areas or the introduction of resistant B. diandrus seeds via contaminated grain should be avoided. [ABSTRACT FROM AUTHOR]

The slow rate of genetic gain for improving resistance to Septoria nodorum blotch (SNB) is due to the inherent complex interactions between host, isolates, and environments. Breeding for improved SNB resistance requires evaluation and selection of wheat genotypes consistently expressing low SNB response in different target production environments. The study focused on evaluating 232 genotypes from global origins for resistance to SNB in the flag leaf expressed in different Western Australian environments. The aim was to identify resistant donor germplasm against historical and contemporary pathogen isolates and enhance our knowledge of the genetic basis of genotype-by-environment interactions for SNB response. Australian wheat varieties, inbred lines from Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), and International Center for Agricultural Research in the Dry Areas (ICARDA), and landraces from discrete regions of the world showed low to moderate phenotypic correlation for disease response amongst genotypes when evaluated with historical and contemporary isolates at two locations across 3 years in Western Australia (WA). Significant (P < 0.001) genotype-by-environment interactions were detected regardless of same or different isolates used as an inoculum source. Joint regression analysis identified 19 genotypes that consistently expressed low disease severity under infection with different isolates in multi-locations. The CIMMYT inbred lines, 30ZJN09 and ZJN12 Qno25, were particularly pertinent as they had low SNB response and highest trait stability at two locations across 3 years. Genome wide association studies detected 20 QTL associated with SNB resistance on chromosomes 1A, 1B, 4B, 5A, 5B, 6A, 7A, 7B, and 7D. QTL on chromosomes 1B and 5B were previously reported in similar genomic regions. Multiple QTL were identified on 1B, 5B, 6A, and 5A and detected in response to SNB infection against different isolates and specific environments. Known SnTox- Snn interactions were either not evident or variable across WA environments and SNB response may involve other multiple complex biological mechanisms. [ABSTRACT FROM AUTHOR]

Climate change has likely impacted crop yield potential in major rain-fed crop-growing regions. However, the impact on the spatial pattern across regions is unclear. Here, the wheat belt of Western Australia was used as a case study to investigate the effect of historical climate change on the spatial patterns of water-limited crop yield. We used 117 years (1900–2016) of observed daily climate data on ~ 5 km × ~ 5 km grids to map and quantify the spatial-temporal changes in water-limited wheat yield simulated by the APSIM model. The climate data were split into four periods based on distinct changes in rainfall (Period 1, 1900–1934; Period 2, 1935–1974; Period 3, 1975–1999; and Period 4, 2000–2016). The results showed that the observed decreases in rainfall shifted the regional wheat yield potential towards the southwest of the wheat belt by an average of 70 km between the first and last periods. Observed increases in CO2 counteracted this by about half of this movement. Actual wheat yields achieved by farmers have not decreased, thanks to improvements in crop genetics and management, but the simulated decrease in water-limited yields has meant that actual yields in this region are not as high as they might have been. Future climate change is likely to continue to impact on water-limited crop yield and its spatial pattern in Western Australia. Cropping systems will need to continually evolve to cope with a changing climate, and every aspect of agronomy and genetics needs to be considered. Without continuing improvements, there will likely be a decrease in wheat yield across this cropping region. [ABSTRACT FROM AUTHOR]

The pathogenic fungal species Pyrenophora tritici - repentis (Ptr) and Parastagonospora nodorum (Pan) are common in many wheat-producing parts of the world. These two fungi cause tan spot and septoria nodorum blotch, respectively, frequently co-infecting wheat leaves. Empirical studies of this and other co-infections are rare because of the visual similarity of symptoms and the lack of robust methods for quantifying the abundance of pathogens associated with the co-infection. Here, we use a recently developed molecular method that simultaneously distinguishes and quantifies, in DNA equivalent, the abundance of Ptr and Pan, thereby allowing the prevalence of co-infection to be determined. The study examines the prevalence of co-infection under field conditions, at three widely spaced sites and on three wheat (Triticum aestivum L.) cultivars varying in disease resistance. Co-infection by Ptr and Pan was almost ubiquitous (overall prevalence 94%), and Pan DNA was detected only in association with Ptr. Although Ptr and Pan commonly co-infected, Ptr was more abundant during early and mid-season, at 80% of total fungal abundance when crops were tillering and 67% at booting stage. Pan became as abundant as Ptr when crops reached flowering. Variability in total fungal abundance and disease severity was primarily determined by cultivar; however, Ptr was the more abundant despite differences in cultivar resistance to this pathogen. We present DNA evidence that the two most common foliar fungal diseases, tan (yellow) spot and septoria nodorum blotch, co-occur in Western Australian wheat fields. Despite their co-occurrence, septoria nodorum blotch occurs only in association with tan spot in the co-infected leaves. We highlight the importance of considering tan spot and septoria nodorum blotch as a complex, and accounting for this complex may be central to successful disease-management efforts. [ABSTRACT FROM AUTHOR]

Introduction: Septoria nodorum blotch (SNB) is a complex fungal disease of wheat caused by the Dothideomycete fungal pathogen Parastagonospora nodorum. The fungus infects through the use of necrotrophic effectors (NEs) that cause necrosis on hosts carrying matching dominant susceptibility genes. The Western Australia (WA) wheatbelt is a SNB "hot spot" and experiences significant under favorable conditions. Consequently, SNB has been a major target for breeders in WA for many years. Materials and Methods: In this study, we assembled a panel of 155 WA P. nodorum isolates collected over a 44-year period and compared them to 23 isolates from France and the USA using 28 SSR loci. Results: The WA P. nodorum population was clustered into five groups with contrasting properties. 80% of the studied isolates were assigned to two core groups found throughout the collection location and time. The other three non-core groups that encompassed transient and emergent populations were found in restricted locations and time. Changes in group genotypes occurred during periods that coincided with the mass adoption of a single or a small group of widely planted wheat cultivars. When introduced, these cultivars had high scores for SNB resistance. However, the field resistance of these new cultivars often declined over subsequent seasons prompting their replacement with new, more resistant varieties. Pathogenicity assays showed that newly emerged isolates non-core are more pathogenic than old isolates. It is likely that the non-core groups were repeatedly selected for increased virulence on the contemporary popular cultivars. Discussion: The low level of genetic diversity within the non-core groups, difference in virulence, low abundance, and restriction to limited locations suggest that these populations more vulnerable to a population crash when the cultivar was replaced by one that was genetically different and more resistant. We characterize the observed pattern as a low-amplitude boom-and-bust cycle in contrast with the classical high amplitude boom-and-bust cycles seen for biotrophic pathogens where the contrast between resistance and susceptibility is typically much greater. Implications of the results are discussed relating to breeding strategies for more sustainable SNB resistance and more generally for pathogens with NEs. [ABSTRACT FROM AUTHOR]

Fusarium crown rot (FCR), caused predominantly by Fusarium pseudograminearum (Fp) in Australia, is an important fungal disease of wheat and barley. FCR causes significant yield losses and reduced grain quality worldwide. This study investigated the population dynamics of FCR‐causing F. pseudograminearum isolates from Western Australia (WA), a major wheat‐growing region. Wheat samples were collected from a total of seven different sites in 2008 and 2015. Two sites, Tammin and Karlgarin, with moderate to high FCR incidence, were intensively sampled in both years. The results revealed significant increase in Fp isolation frequency between 2008 and 2015. Over 86% of 1100 Fusarium isolates were Fp in 2015 compared with 59% of 639 isolates from 2008. Mating type idiomorphs, toxin chemotypes and population genetic structures were determined for a subset of 279 Fp isolates (132 isolates from 2008 and 165 from 2015). Mating type analysis revealed differences in MAT1‐1 and MAT1‐2 distributions between Tammin and Karlgarin for both years. Results also showed that 97.6% of Fp isolates analysed had the 3‐ADON trichothecene chemotype. Additionally, for the first time in Australia, the 15‐ADON chemotype was identified in 2.3% and 2.4% of Fp isolates from 2008 and 2015, respectively. The genetic structure of Fp population determined using 21 cleaved amplified polymorphic sequence (CAPS) markers revealed a high level of genetic variation within and between populations. In addition, 2015 isolates from Tammin and Karlgarin were significantly more aggressive (P < 0.0001) than 2008 isolates. This finding may have implications in managing this significant fungal disease. [ABSTRACT FROM AUTHOR]

• Fusarium spp. and Rhizoctonia solani were favoured by cereal dominated rotations. • Pythium spp. and Pratylenchus neglectus were favoured by more diverse rotations. • Windrow burning had little effect on amount of stubble-borne disease. • Farmers require up-to-date information on the crop host status. No-tillage is a cropping system that promotes minimal soil disturbance, full residue retention and diverse crop rotation. From a disease perspective, crop rotation is one of the best control measures in no-tillage systems, as many diseases are stubble-borne. A long-term no-tillage systems experiment was conducted from 2007 to 2016 in Western Australia to test effects of crop rotation and residue amount on soil health, crop growth and yield. The current research focusses on the progression of the main stubble-borne and root diseases and plant-parasitic nematodes in this experiment. The research compared a diverse crop rotation with a 'typical' farmer rotation, a cereal rotation and wheat monoculture. Three-year rotations were used and the crops and cultivars were changed periodically, within the rotations, to ensure they were relevant to farmers. Levels of root lesion nematode (Pratylenchus neglectus) and Pythium increased most in the pasture and diverse rotations, followed by the wheat monoculture and appeared to decrease slightly in the farmer and cereal rotations. The combination of canola and wheat, along with susceptible chickpea, appeared to favour root lesion nematode. In contrast, fallow and lupin in the farmer rotation appeared most effective at reducing levels. The relatively high numbers of P. neglectus in the pasture was likely due to continuous presence of a number of susceptible weeds and subterranean clover. The crop selections in the diverse rotation of this experiment have generally been a poor choice in terms of P. neglectus, the main nematode threat in Western Australia. By 2016, there was significantly greater Rhizoctonia solani in the soil following cereals compared with canola, chickpea and fallow. Nonetheless, the break crops appeared to have had a relatively short term effect on amounts of R. solani. Over the nine years, Fusarium spp. DNA in the soil increased most in the cereal rotation and wheat monoculture; it hardly changed in the farmer rotation and pasture and it declined in the diverse rotation. There was a decrease in Didymella pinodes / Phoma medicaginis var pinodella DNA (causing pea black spot) in the cereal rotation, farmer rotation and wheat monoculture. In contrast, there was a small increase in pea black spot pathogen DNA in the diverse rotation. This generally reflected the number of pea crops grown, except for the farmer rotation, which had peas grown at the same intensity as the diverse rotation. The difference between these two rotations was likely due to the lower amounts of residue in the farmer rotation, which had fallow and tillage since 2013. As expected, there were higher incidence of the stubble-borne disease in wheat and barley when following the same type of crop. Crop residue management, by windrow burning, had little effect on the level of leaf, root or crown diseases. The differences in host status between crop types and even varieties means that farmers require up-to-date information on the host status if rotations are going to be effective in reducing a broad range of plant-parasitic nematodes and pathogens in soils with no-tillage. [ABSTRACT FROM AUTHOR]

With increasing canola (Brassica napus L.) acreage in the Inland Pacific Northwest of the USA, we investigated the effect of this relatively new rotational crop on soil microbial communities and the performance of subsequent wheat (Triticum aestivum L.) crops. In a 6-year on-farm canola-wheat rotation study conducted near Davenport, WA, grain yields of spring wheat (SW) following winter canola (WC) were reduced an average of 17% compared to SW yields following winter wheat (WW). Using soil samples collected and analyzed every year from that study, the objective of this research was to determine the differences and similarities in the soil microbial communities associated with WC and WW, and if those differences were associated with SW yield response. Microbial biomass and community composition were determined using phospholipid fatty acid analysis (PLFA). The WC-associated microbial community contained significantly less fungi, mycorrhizae, and total microbial biomass than WW. Additionally, reduced fungal and mycorrhizal abundance in SW following WC suggests that the canola rotation effect can persist. A biocidal secondary metabolite of canola, isothiocyanate, may be a potential mechanism mediating the decline in soil microbial biomass. These results demonstrate the relationship between soil microbial community composition and crop productivity. Our data suggest that WC can have significant effects on soil microbial communities that ultimately drive microbially mediated soil processes. [ABSTRACT FROM AUTHOR]

Yield prediction is a major determinant of many management decisions for crop production. Farmers and their advisors want user-friendly decision support tools for predicting yield. Simulation models can be used to accurately predict yield, but they are complex and difficult to parameterise. The goal of this study is to build a simple and parsimonious model for predicting wheat yields that can be implemented in a decision tool to be used by farmers at a paddock level. A large yield data set accumulated from trials on commonly grown varieties in Western Australia is used to build and validate a generalised additive model (GAM) for predicting wheat yield. Explanatory variables tested included weather data and derivatives, geolocation, soil type, land capability, and wheat varieties. Model selection followed a forward stepwise approach in combination with cross-validation to select the smallest set of explanatory variables. The predictive performance is also evaluated using independent data. The final model uses seasonal water availability, location and year to predict wheat yield. Because the GAM model has minimal inputs, it can be easily employed in a decision tool to predict yield throughout the growing season using rainfall data up to the prediction date and either climatological averages or seasonal forecasts of rainfall for the remainder of the growing season. It also has the potential to be used as an input to agronomic models that predict the effect on yield of various management choices for fertiliser, pest, weed and disease management. • Wheat yields in Western Australia are driven by seasonal rainfall. • Yields can be predicted using a simple model with few, easily obtained inputs. • The model can be easily implemented in an online decision tool or mobile app. [ABSTRACT FROM AUTHOR]

The Australian wheat industry is an important contributor to the Australian economy and farm sector. This paper investigates the determinants of land use and profitability in wheat production for the Australian wheat-sheep zone. Wheat area supply response and its profitability were estimated across the wheat-sheep zone for the period 1990-2015. The results indicated that the growers in Western Australia are more (relative expected) price responsive than the growers in the South Eastern states. The current wheat area is highly depended on the previous year's wheat area, and the area adjustment is also not significantly different between the regions. Estimates for own-price (wheat-wheat) and cross-price (wheat-wool) elasticities are with the expected signs, and the cross-price elasticities are more inelastic compared to the own price elasticities. Wheat productivity influenced negatively by the area sown but showed the positive influence of locations and periods, which implies technological progress has been playing a significant role to improve wheat production. Ricardian approach for wheat profitability indicates the regional effect of minimum temperature on determining wheat net revenue in the Australian wheat-sheep zone. [ABSTRACT FROM AUTHOR]

Agricultural operations routinely expose farm workers to high levels of soil dust and other airborne particulate matter that have been linked to adverse health outcomes. The main objective of this study was to investigate exposure to agricultural dust during seeding operations of Western Australian farm workers. Twenty-one wheat-belt farms were recruited to participate in the study. Data were collected over the 6-week seeding period of April-June 2014. Each farm was visited once, and workers were asked to complete a workplace survey that asked questions related to minimizing exposure to agricultural dusts and occupational health and safety issues on their farm. Farmers were also asked to simultaneously participate in monitoring of personal exposure to inhalable or respirable dust along with real-time monitoring for particulate air pollution in their tractor cabin. Sampling was undertaken for 4 hr. The results showed that, on average, Western Australian farmers were exposed to personal respirable dust concentrations above the Australian Institute of Occupational Hygienists recommended guideline values, with some farmers being exposed to concentrations up to seven times higher than the value for respirable dusts. In comparison, in-cabin dust concentrations were lower, although some individual tractors recorded intermittently higher levels, which might be attributed to the type of work activity or process being undertaken. Remaining in tractor cabins with closed doors and windows with properly maintained seals might minimize the infiltration of hazardous dusts and may provide some protection from dust exposures. Future research should focus on educating and providing farm owners and workers with more information on adopting work processes and procedures related to minimizing harmful exposures to agricultural dusts. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is a major factor limiting grain production in the high rainfall zone (HRZ, 450–700 mm annual average rainfall of southwestern Australia (SWA). Transient waterlogging and leaching of applied N fertilizer are hazards faced in most years by crop producers. The major crops are wheat (Triticum aestivumL.), barley (Hordeum vulgareL.), canola (Brassica napusL.) and lupin (Lupinus angustifioliusL.) grown in rotation. Two series of experiments involving, levels and timing of N fertilizer application and levels of plant population were done. The first series, in 2003–2004, consisted of 3 experiments in 3 growing seasons (early May to late-October) to measure the grain yield (GY) increase (response) of wheat and barley to various methods of N fertilizer application (methods of split N application were compared to N applied at sowing). The aim of the experiments was to determine the optimal N fertilizer application strategy for maximum GY and quality in situations where transient waterlogging was a frequent occurrence. The second series of four experiments, from 2007–2009, measured the GY of wheat sown at three levels of plant population to 4 levels of N applied after transient waterlogging (taken to be rainfall events in which >25 mm of rain was recorded in 24 to 48 hours). Applying the N fertilizer after high rainfall and transient waterlogging (tactical N application) increased GY and protein percentage of grain compared to applying all of the N fertilizer at sowing. Where transient waterlogging was not frequent, applying the N after waterlogging was not always better than applying part of the N according to growth stage of the crop or according to fixed times after sowing. When the crop was water-logged three or more times, N uptake by the crop at anthesis and apparent fertilizer N recovery in the crop was substantially increased by applying the N after waterlogging compared to applying the entire N at sowing. This study found that a tactical N management strategy for the HRZ of SWA is to apply some N at sowing with subsequent applications made after heavy rainfall that leads to transient waterlogging. Split N fertilizer applied either according to time after sowing or to growth stage of the crop was equally effective for increasing GY in situations where waterlogging was less frequent. The observation from these experiments, that grain yield increases due to splitting the N dose were associated with increases in ear numbers, lead to a further set of experiments where plant population was increased in conjunction with N applied after waterlogging events. The combined strategy of increased plant population with strategic N application decreased the amount of N required for maximum GY where more than 3 heavy rainfall events occurred in a growing season. One practical outcome of this research is to indicate that farmers can withhold applications of N fertilizer after sowing in seasons when transient waterlogging does not occur. [ABSTRACT FROM AUTHOR]

This research aimed to clarify the evolution of textural characteristics and in vitro digestibility under different storage conditions. Quickly increasing hardness and decreasing resilience was observed in quinoa bread after 5d cold (4 °C) storage. However, when stored at −18 °C for 5d, bread crumb still maintains a dense alveographic with 52.33% of cell density and 33.76% area fractions. In addition, the starch digestion rate decreased with increasing retrogradation degree. Scanning electron microscope (SEM) characterizations illustrated that the chunky matrix gradually disappeared with digestion. However, quinoa starch (QS) granules were the most difficult to digest owing to the relative intactness and wrapping in the protein-starch bulk. Meanwhile, X-ray diffraction (XRD) showed that the crystal structure of starch remained 21.09% stored in frozen conditions, and wheat type-A (WA) starch was mainly involved in gelatinization. The results of water migration proved that water participated in the retrogradation of starch and affected the quality of quinoa bread. Overall, bread stored in frozen conditions can maintain good texture characteristics and slow starch digestion rate. This study indicates that quinoa flour fortified bread has the potential to be developed as staple food with both low glycemic index values and storage stability. [Display omitted] • Cold storage accelerated starch retrogradation and bread staling. • The texture was affected by starch retrogradation and the change of water state. • Bread stored at frozen condition was more conducive to digestion. • A-type wheat starch mainly participated in the gelatinization and aging process. • Quinoa and B-type wheat starch with small particles digested slowly after storage. [ABSTRACT FROM AUTHOR]

The Western Australian wheat-belt has experienced more rainfall decline than any other wheat-cropping region in Australia. Future climate change scenarios suggest that the Western Australian wheat-belt is likely to see greater future reductions in rainfall than other regions, together with a further increase in temperatures. While these changes appear adverse for water-limited rain-fed agriculture, a close analysis of the changes and their impacts reveals a more complex story. Twentieth century changes in rainfall, temperature and atmospheric CO concentration have had little or no overall impact on wheat yields. Changes in agricultural technology and farming systems have had much larger impacts. Contrary to some claims, there is no scientific or economic justification for any immediate actions by farmers to adapt to long-term climate change in the Western Australian wheat-belt, beyond normal responses to short-term variations in weather. Rather than promoting current change, the most important policy response is research and development to enable farmers to facilitate future adaptation to climate change. Research priorities are proposed. [ABSTRACT FROM AUTHOR]

The long term archiving of both Landsat imagery and wheat yield mapping datasets sensed by precision agriculture technology has the potential through the development of statistical relationships to predict high resolution estimates of wheat yield over large areas for multiple seasons. Quantifying past yield performance over different growing seasons can inform agricultural management decisions ranging from fertilizer applications at the sub-paddock scale to changes in land use at a landscape scale. However, an understanding of the magnitude of prediction errors is needed. In this study, we examine the predictive wheat yield relationships developed from Normalised Difference Vegetation Index (NDVI) acquired Landsat imagery and combine-mounted yield monitors for three Western Australian farms over different growing seasons. We further analysed their predictive capability when these relationships are used to extrapolate yield from one farm to another. Over all seasons, the best predictions were achieved with imagery acquired in September. Of the five seasons reviewed, three showed very reasonable prediction accuracies, with the low and high rainfall years providing good predictions. Medium rainfall years showed the greatest variation in prediction accuracy with marginal to poor predictions resulting from narrow ranges of measured wheat yield and NDVI values. These results demonstrate the potential benefit of fusing together two high resolution datasets to create robust wheat yield prediction models over different growing seasons, the outputs of which can be used to inform agricultural decision making. [ABSTRACT FROM AUTHOR]

Objective In September 2009, Australia implemented mandatory folic acid fortification of wheat flour for bread-making to reduce the incidence of neural tube defects. Our study aimed to establish baseline folate status data in Aboriginal and non- Aboriginal Western Australians. Methods Patients who presented at a health service or collection centre for blood tests were invited to participate. One hundred and ninety-one Aboriginals and 159 non- Aboriginals were recruited between April 2008 and September 2009. Participants completed a five-minute questionnaire and had blood taken for red blood cell ( RBC) folate and serum vitamin B12. Data were analysed using SPSS (version 17.0.2, SPSS Inc., Chicago, IL, USA). Results Ten per cent (95% confidence intervals ( CI): 5, 19) of the Aboriginal women participants and 26% (95% CI: 16, 40) of men had RBC folate concentrations below 250 ng/mL, the cut-off associated with folate deficiency. None of the non- Aboriginal women (95% CI: 0, 4) and 4% of the non- Aboriginal men (95% CI: 2, 12) had RBC folate concentrations below 250 ng/mL. All participants were vitamin B12 replete. None of the 96 Aboriginal and 8% of non- Aboriginal women aged 16-44 reported consumption of supplements with a daily intake of >400 μg folic acid during the previous week. Conclusions and implications This study established a baseline of RBC folate, folate consumption and supplement use in Aboriginal and non- Aboriginal groups. We identified 10% of Aboriginal women and none of non- Aboriginal women participants with low folate concentrations. The higher prevalence of folate deficiency in Aboriginal participants suggests they are more likely to benefit from a universal program of folate fortification. [ABSTRACT FROM AUTHOR]

Abstract: Achievable grain yields can vary widely between seasons in rain-fed agriculture. Adjusting N fertiliser inputs according to achievable grain yields could reduce over-fertilisation in low-yielding seasons and allow increasing gross margins in potential high-yielding seasons. Seasonal rainfall forecasts from the coupled ocean-atmosphere global circulation model POAMA were skill tested and employed for N fertiliser decision making in the Western Australian wheat-belt. The POAMA seasonal rainfall forecast showed significant skill in forecasting rainfall season types in southern regions of the Western Australian wheat-belt. This skill resulted in about A$50ha−1 of additional benefits when used in N management decisions in wheat cropping. However, such a forecast should not be used without considering other systems knowledge available to farmers. Combining a forecast with systems information such as initial soil water conditions can be crucial in obtaining value from a forecast. Another important factor to consider is the risk behaviour of farmers, where the gross margin from additional fertiliser is expected to exceed the cost by a factor of two or more. Finally, variations in fertiliser cost and wheat prices are critical in determining the benefits from using a forecast system for management decisions in agriculture. Using a forecast for only the wet season-type can further increase a forecast value because the additional gains in wet seasons are often higher than the savings from reduced fertiliser in dry seasons. It is expected that skilful seasonal forecasting systems will become increasingly valuable in regions where rainfall is decreasing because they help to capture benefits in the declining number of potentially high-yielding seasons and minimise the losses in the increasing number of low-yielding seasons. [Copyright &y& Elsevier]

Aims: Despite our current understanding of plant nitrogen (N) uptake and soil N dynamics in arable systems, the supply and demand of N are infrequently matched as a result of variable seasonal and soil conditions. Consequently, inefficiencies in N utilisation often lead to constrained production and can contribute to potential environmental impacts. The aim of this study was to examine the influence of plant residue quality (C/N ratio) and extent of residue incorporation into soil on temporal changes in soil mineral N and the associated plant N uptake by wheat in the semi-arid agricultural production zone of Western Australia. Methods: Oat ( Avena sativa); lupin ( Lupinus angustifolius) and field pea ( Pisum sativum) were incorporated into a Red-Brown Earth using varying degrees of mechanical disturbance (0 to 100% residue incorporated). Soil samples for inorganic N (NO and NH) profiles (0-50 cm), microbial biomass-C (0-50 cm) and plant N uptake were taken throughout the growing season of the subsequent wheat ( Triticum aestivum) crop. Grain yield and yield components were determined at harvest. Results: Despite observed treatment effects for plant residue type and soil disturbance, fluctuations in inorganic N were more readily influenced by seasonal variability associated with wet-dry cycles. Treatment effects resulting from residue management and extent of soil disturbance were also more readily distinguished in the NO pool. The release of N from crop residues significantly increased ( p = 0.05) with greater soil-residue contact which related to the method of incorporation; the greater the extent of soil disturbance, the greater the net supply of inorganic N. Differences in microbial biomass-C were primarily associated with the type of plant residue incorporated, with higher microbial biomass generally associated with legume crops. No effect of residue incorporation method was noted for microbial biomass suggesting little effect of soil disturbance on the microbial population in this soil. Conclusions: Despite differences in the magnitude of N release, neither crop type nor incorporation method significantly altered the timing or pattern of N release. As such asynchrony of N supply was not improved through residue or soil management, or through increased microbial biomass in this semi-arid environment. N fluxes were primarily controlled by abiotic factors (e.g. climate), which in this study dominated over imposed agricultural management practices associated with residue management. [ABSTRACT FROM AUTHOR]

Despite apparent climatic and edaphic similarities with traditional growing areas in the Mediterranean basin, durum wheat has not been grown extensively as a commercial crop in Western Australia. The principal objective of this study was to develop some effective agronomic management practices as one of the first steps in introducing durum wheat cultivation into Western Australia and to compare the responses to those found in more traditional areas in the world where durum is successfully grown. Twenty-seven experiments were conducted in 1998, 1999, 2000 and 2001 in the northern, central, and southern wheat belt of Western Australia using treatments which included: two durum wheat cultivars (Triticum turgidum L. subsp. durum (Desf.) Husn.) and two bread wheat cultivars (T. aestivum L.); 3 sowing times; 5 nitrogen (N) rates and; 5 seeding rates. The experiments were conducted on a range of soil types and the seasonal rainfall ranged from 70 to 347 mm. The average yield advantage for bread wheat cultivars over durum wheat cultivars was 13 - 19% depending on site and season. The average grain protein percentage for durum cultivars was between 0.8 and 1.5% greater than for the bread wheat cultivars. Overall, it was concluded that durum wheat could be grown successfully in Western Australia using the practices resulting from the experiments described in this paper but that the long term success of the crop will depend on reducing the yield gap between bread wheat and durum wheat and on the continued quality and price advantage for durum wheat. [ABSTRACT FROM AUTHOR]

Early vigour in wheat (Triticum aestivum) is an important physiological trait to improve water-use efficiency and grain yield, especially on light soils in Mediterranean-type climates. Potential interactions for plant stand and seedling vigour between seed density and various seed quality treatments were examined for wheat grown in two experiments, conducted under controlled and field environments in Western Australia. Seed lots were graded into seed size classes and seed density fractions using saturated solutions of ammonium sulphate or sodium polytungstate. Dense seed improved plant stands or produced seedlings with greater early seedling vigour than their low-density counterparts in all three field environments. Artificial ageing reduced germination and emergence in the controlled environment. When grown in the field at Merredin, Western Australia, on the sandy soil, plant development was delayed with aged seed, and total leaf area and dry weight of plants were reduced. Fungicide application diminished total plant dry weight in sandy soils, but had a much larger detrimental effect when applied to aged and low-density seeds than normal seeds, retarding development, total leaf area and total plant dry weight. Our results indicate that an increase in seed density, particularly in small seed, can potentially improve plant stand and seedling vigour independently of seed size, and may be especially important for wheat grown on sandy soils of poor fertility and low water-holding capacity. The results also suggest consistency in seedling vigour may benefit from combined screening against small seed size and low seed density, which may also reduce the likelihood of adverse reactions to seed-applied fungicides. More attention should be paid to seed density as a valuable trait for improved reliability in plant stand and seedling vigour. [ABSTRACT FROM PUBLISHER]

This paper investigates the key decision parameters of farmers related to the allocation of land between wheat production and pasture for sheep (wool) production. Wheat area supply response, is estimated across the Australian wheat-sheep zone using data for the period 1991 to 2004. Statistical results reveal that wheat growers in Western Australia are more price responsive than growers in the eastern states. Area adjustment is not significantly different between the regions. Rainfall has a positive influence on wheat production while time-related exogenous factors such as technical progress seemed to have little influence on the wheat yield over this period. [ABSTRACT FROM AUTHOR]

Abstract: The high prevalence (14 of 24 isolates) of enniatin-producing isolates from Western Australian Fusarium species isolated from pasture legumes associated with sheep feed refusal and rat deaths, and the high toxicity of their crude extracts to brine shrimp (Artemia franciscana) from a previous study warranted further investigation of this class of mycotoxin. Crude extracts from Fusarium acuminatum, Fusarium avenaceum, Fusarium tricinctum and Fusarium sambucinum, along with enniatins A, A1, B and B1 purified from a Western Australian strain of F. acuminatum using semi-preparative HPLC, were bioassayed using brine shrimp. All Fusarium isolates produced both enniatins B and B1, except for F. tricinctum WAC 8019, and 11 of the 17 isolates produced enniatin A1. Overall, all of the F. avenaceum isolates produced high amounts of enniatins, in particular enniatin B. One isolate of F. acuminatum (WAC 5715) and of F. tricinctum (WAC 11486) also produced high amounts of both enniatins B and B1. Only F. acuminatum WAC 5715 produced enniatin A among the tested isolates. All four purified enniatins A, A1, B, B1, individually and in combination, caused brine shrimp toxicity after 6 h of exposure, implicating that this emerging class of mycotoxin as a cause of the acute toxicity to brine shrimp observed. The mixture of all four enniatins was the most toxic to brine shrimp compared to purified individual enniatins, where the relative toxicity order was B > B1 > A1 > A. Enniatin B was the individual most toxic enniatin with some bioactivity at 5 μg/mL and almost 100% brine shrimp death at 50 μg/mL after 24 h of exposure. This study is the first report to confirm the acute toxicity of enniatins A, A1, B and B1 to brine shrimp, and also highlights the need for further investigation of the potential toxicity of these cyclic hexadepsipeptides to animals and humans. [Copyright &y& Elsevier]

Wheat growers in Western Australia (WA) value flowering date predictions for risk aversion from frost and terminal stresses. Currently used statistical models such as the "flowering calculator" (referred to as photothermal model as programmed by Tennant and Tennant [2000] [TT]) are less robust in colder regions and/or higher latitudes of WA. We developed a new statistical model (named DM) that includes a vernalization component in addition to photoperiod and temperature components, the three biological drivers of reproductive growth and development in wheat (Triticum spp.). The model assumes that heatsums required for flowering comprise a variety specific minimum, plus some more that are linearly contingent on sowing day, daylength, and the statistical summaries of daily temperature profiles. The vernalization opportunity was quantified using a term named "coldsum" calculated as equal to the sum of daily periods under 5°C in hourly temperature profile, while "heatsum" referred to the periods above 0×C. Environments were characterized using a log-log transformation on heatsums and a segmented-lines approach on coldsums. The model coefficients were estimated using data from four sowing dates spanning prevalent sowing times in WA over 4 yr at three diverse locations. The DM predictions were statistically far superior to TT (F probability < 0.001; RMSD 6.1 and 17.4, respectively) in all respect of location, season, sowing date, and cultivar factors when compared in independent datasets from six cultivar × sowing date trials across WA wheatbelt. Since DM relies on a structured application of seasonal profiles, it should be applicable to other geographic areas, cultivars, and crops. [ABSTRACT FROM AUTHOR]

As herbicide-resistant weeds have spread in the agricultural fields of grain-exporting countries, their seeds could be introduced into other countries as contaminants in imported grain. The spread of resistance genes through seed and pollen can cause significant economic loss. In order to assess the extent of the problem, we investigated the contamination by herbicide-resistant annual ryegrass ( Lolium rigidum) of wheat imported from Western Australia into Japan. Annual ryegrass seeds were recovered from wheat shipments and seed bioassays were conducted to identify resistance to the herbicides that are commonly used in Australia: diclofop-methyl, sethoxydim, chlorsulfuron, and glyphosate. Nearly 4500 ryegrass seeds were detected in 20 kg of wheat that was imported in both 2006 and 2007. About 35% and 15% of the seeds were resistant to diclofop-methyl, 5% and 6% were resistant to sethoxydim, and 56% and 60% were resistant to chlorsulfuron in 2006 and 2007, respectively. None was resistant to glyphosate in either year. As the contamination of crops by herbicide-resistant weeds is probably a common phenomenon, the monitoring of incoming grain shipments is necessary to stem the further spread of herbicide-resistant weeds into importing countries. [ABSTRACT FROM AUTHOR]

Abstract: In the Mediterranean farming systems of the Western Australian wheatbelt, crop yields are influenced primarily by the amount and distribution of rainfall and the soil''s capacity to hold moisture. The wheatbelt''s growing season rainfall varies in the range of 200–400mm (average) and the plant available water holding capacity (PAWC) of soils is generally in the 40–140mm range. The grain yield of wheat is sensitive to this combination of small rainfall and small storage capacity. In this study, we explore the relationship between yield and PAWC using a combination of simulation modelling and analysis of field data. Crop yields and soil properties were monitored in detail at 17 locations (PAWCs 43–131mm) across six seasons (1997–2005). Crop yields were also simulated using the APSIM crop simulator (RMSE=311kg/ha) to evaluate the long-term relationship between crop yield and plant available water capacity using 106 years of historical climate data. The relationship between crop yield and PAWC varied with season, and two important factors emerged: (1) for PAWC<65mm, there was a linear relationship with crop yields that ranged from 17kg/ha/mm to 58kg/ha/mm of PAWC across seasons; (2) for PAWC 65–131mm the crop yield response to PAWC ranged from 11.5kg/ha/mm in 45% of seasons to no response. The impact of PAWC on crop yield was reduced in seasons with late rainfall, and magnified in seasons with reduced rainfall late in the growing season. Six distinct season types with different yield–PAWC relationships are identified and season-specific management strategies that exploit within-field variation in PAWC are developed to manage the spatial variation of PAWC in a field. [Copyright &y& Elsevier]

A two-layer steady-state resistance model is compared with routine meteorological data collected from the Western Australian wheat belt during 2000–06. Major difficulties in implementing such a model are the correct parameterization for the incoming longwave radiation and estimation of daily soil moisture, neither of which are routinely measured. These difficulties are addressed by testing parameterizations for incoming longwave radiation calibrated to local conditions and incorporating a soil–water balance model based on routine weather data. The modified model has RMSE and biases ranging from 2.4° to 3.1°C and -0.2° to 0.8°C, respectively, across the wheat belt when comparing all minimum nocturnal temperatures. The model is shown to predict frost events approximately 55% of the time and illustrates that frost damage to foliage may occur when screen temperatures are < 2°C. [ABSTRACT FROM AUTHOR]

In situ 15N-labelling was used to provide a quantitative assessment of the total contribution of lupin ( Lupinus angustifolius) to below-ground (BG) N accumulation during a growing season under field conditions, and to directly trace the fate of the lupin BG N in the next season, including quantifying the N benefit from lupin to a following wheat ( Triticum aestivum) crop. The experiments were conducted at two sites, both experiencing a semi-arid Mediterranean-type climate in the wheat-growing region of Western Australia but with differing soil types, a deep sand (Moora) and a sand-over-clay shallow duplex soil (East Beverley, EB). Lupin shoot and root dry matter and total plant N accumulation, proportional dependence on nitrogen fixation and grain yield were greater at the deep sand site than the duplex soil site, although there was a similar proportion of shoot N to estimated total BG N at both sites. The proportion of total plant BG N decreased from the vegetative stage (42–51%) to peak biomass (25–39%) and maturity (23–34%). From 56–67% of BG N on the deep sand and 74–86% on the duplex soil was not recovered in coarse roots (>2 mm) or as soluble N, but was present in the insoluble organic N fraction. There was evidence for cycling of lupin root-derived N into soil microbial biomass and soluble organic N during lupin growth (by the late vegetative stage), but no evidence for leaching of legume derived BG N during the lupin season. Estimates of fixed N input BG were at least four times greater if based on total lupin BG N rather than on N recovered in coarse roots (>2 mm). There were no apparent losses of lupin BG N during the summer fallow period subsequent to lupin harvest at either site. Also, immediately prior to sowing of wheat there were similar proportions of lupin BG N in the inorganic (20–25%) and microbial biomass (6–9%) pools at both sites, with the majority of BG N detected in the <2 mm fraction of the soil column. However, the proportion of residual lupin BG N estimated to benefit the aboveground wheat biomass was relatively low, 10% on the deep sand and only 3% on the shallow duplex. Some (14%) residual lupin BG N was leached as nitrate to 1 m on the deep sand compared to 8% of residual lupin BG N leached to the clay layer (0.3 m) on the shallow duplex. About 27% of the residual lupin BG N on the deep sand at Moora had apparently mineralised by the end of the succeeding wheat season (i.e. recovered either in the wheat shoots, as inorganic N in the soil profile or as leached nitrate) compared to only 12% at EB. There was an unaccounted for large loss of residual lupin BG N (50%) from the duplex soil at EB during the wheat season, postulated to be chiefly via denitrification. At both sites after the wheat season a substantial proportion (32–55%) of legume derived BG N was still present as residual insoluble organic N, considered to be an important contribution to structural and nutritional long-term sustainability of these soils. [ABSTRACT FROM AUTHOR]

In 2003, a random survey was conducted across the Western Australian wheatbelt to establish the extent and frequency of herbicide resistance in Raphanus raphanistrum populations infesting crop fields. Five hundred cropping fields were visited, with 90 R. raphanistrum populations collected, representative of populations present in crop fields throughout the Western Australian wheatbelt. Collected populations were screened with four herbicides of various modes of action that are commonly used for the control of this weed. The majority of Western Australian R. raphanistrum populations were found to contain plants resistant to the acetolactate synthase (ALS)-inhibiting herbicide chlorsulfuron (54%) and auxin analogue herbicide, 2,4-D amine (60%). This survey also determined that over half (58%) of these populations were multiple resistant across at least two of the four herbicide modes of action used in the screening. Only 17% of R. raphanistrum populations have retained their initial status of susceptibility to all four herbicides. The distribution patterns of the herbicide-resistant populations identified that there were higher frequencies of resistant and developing resistance populations occurring in the intensively cropped northern regions of the wheatbelt. These results clearly indicate that the reliance on herbicidal weed control in cropping systems based on reduced tillage and stubble retention will lead to higher frequencies of herbicide-resistant weed populations. Therefore, within intensive crop production systems, there is a need to diversify weed management strategies and not rely entirely on too few herbicide control options. [ABSTRACT FROM AUTHOR]