Context Red leather leaf (RLL), caused by Neospermospora avenae, is a common foliar disease of oats in south-eastern Australia but its impact on hay and grain yield and quality is unknown.Aim We aimed to determine the effect of RLL on grain yield and quality of commercial milling oat varieties, and biomass and nutrition of hay oat varieties, with a range of host plant resistance responses by comparing fungicide and disease treatments.Methods A total of eight field experiments were conducted in 2019 and 2020; four experiments each investigated the effects of RLL on hay or milling oats. In each experiment, six or seven oat varieties were sown with a disease or fungicide imposed. RLL severity was estimated visually for each experiment. Biomass yield and quality traits at early milk development stage were measured for hay oat experiments; and grain yield and quality for the milling oat experiments.Key results RLL severity (% leaf area affected: 0-44% in hay oats and 2-61% in milling oats) varied with the season, varietal resistance, and treatments. RLL caused significant losses in most experiments, with reductions in biomass of up to 3.5 t/ha (22%) in hay oats and grain yield of up to 1.1 t/ha (21%) in milling oats.Conclusions RLL can be a severe foliar disease of oats in south-eastern Australia and cause significant losses in both hay and milling oat crops.Implications Growing varieties with resistance can effectively reduce potential loss due to RLL and growers are required to adapt fungicide strategies reflecting seasonal conditions and product type (grain or hay).

Tan spot (TS), known in Australia as yellow leaf spot, is caused by the fungal pathogen Pyrenophora tritici-repentis, a major foliar disease of wheat. Four experiments were conducted between 2016 and 2017 in two different climatic zones of southeastern Australia to determine the impact of TS on grain yield and quality in six wheat cultivars with different resistance ratings. In each experiment, high and low TS disease scenarios were applied to each cultivar. Disease severity was assessed as either whole-plot percentage leaf area affected (%LAA) or top three leaf (flag to flag-2) %LAA. Whole-plot %LAA was analyzed using both repeated measurements and area under the disease progress curve (AUDPC). For whole-plot %LAA, the repeated measurements identified differences in epidemic progression at key growth stages not identified through AUDPC. Both AUDPC and end-of-season flag to flag-2 %LAA were negatively correlated with grain yield and screenings. Increased rainfall impacting disease development and number of rain days above 5 mm increased TS severity across both climatic zones. Cultivar resistance ratings influenced grain yield loss, with moderately resistant, moderately susceptible, and susceptible cultivars losing up to 6, 18, and 24% grain yield, respectively. High disease significantly increased screenings by up to 1, 3, and 5% for moderately resistant, moderately susceptible, and susceptible cultivars, respectively. This study demonstrated that TS can cause significant grain yield losses in southeastern Australia, and a minimum cultivar rating of moderate resistance to moderate susceptibility was required to prevent severe TS and associated grain yield and quality losses. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Spot form net blotch, caused by Pyrenophora teres f. maculata, is a major foliar disease of barley worldwide. Knowledge of the pathogen's genetic diversity and population structure is critical for a better understanding of inherent evolutionary capacity and for the development of sustainable disease management strategies. Genome-wide, single nucleotide polymorphism data of 254 Australian isolates revealed genotypic diversity and an absence of population structure, either between states, or between fields and cultivars in different agro-ecological zones. This indicates there is little geographical isolation or cultivar directional selection and that the pathogen is highly mobile across the continent. However, two cryptic genotypic groups were found only in Western Australia, predominantly associated with genes involved in fungicide resistance. The findings in this study are discussed in the context of current cultivar resistance and the pathogen's adaptive potential.

Spot form of net blotch (SFNB), caused by Pyrenophora teres f. maculata is a prevalent and damaging foliar disease of barley (Hordeum vulgare). Fungicides are commonly used to manage SFNB infection and reduce production loss in susceptible varieties. This study determined the efficacy of suppression of SFNB and associated grain yield and quality improvements from application of fungicides to seed, fertiliser and/or foliar treatments. Eight field experiments were conducted in south-eastern Australia during 2016-2018. Two experiments compared single applications of different commercially available seed, fertiliser and foliar fungicides. Six experiments evaluated different growth stage application timings of either a single application or combinations of seed applied fluxapyroxad and foliar applied prothioconazole + tebuconazole. Spot form of net blotch caused grain yield loss of up to 1.2 t/ha (20%), reduced grain retention (percentage seed width greater than 2.5 mm) and weight by up to 15% and 13%, respectively, and increased screenings (percentage seed width less than 2.2 mm) by up to 18%. Seed applied fluxapyroxad was the most effective fungicide treatment providing the greatest SFNB suppression, grain yield and quality increase of the single fungicide applications. The combination of seed applied fluxapyroxad with a foliar application of prothioconazole + tebuconazole at flag leaf emergence significantly increased grain yield and quality further in one experiment. The dual foliar fungicide application of prothioconazole + tebuconazole at stem elongation (Z31) and flag leaf emergence (Z39) was not as effective in providing SFNB suppression according to AUDPC but provided comparable grain yield and quality to the seed and foliar treatment. Of the foliar fungicides, prothioconazole + tebuconazole and bixafen + prothioconazole provided the best SFNB suppression, grain yield and quality. These fungicide applications strategies provide improved SFNB management options for barley growers, particularly in high yielding crops where grain yield exceeds 5 t/ha.

Net blotches are the most widely distributed foliar diseases of barley worldwide, causing significant losses in grain yield. They occur as net form net blotch, caused by Pyrenophora teres f. teres and spot form net blotch caused by P. teres f. maculata. Both sexual and asexual reproduction play a role in the P. teres disease cycles leading to changes in genetic variation of populations. Breeding programs have to keep pace with pathogenic changes and ensure different sources of resistance are present in current barley cultivars. Knowledge of the genetic architecture and genes involved in virulence is thus vital to increase the durability of net blotch resistance in barley cultivars. This chapter explores the molecular biology, life-cycle and epidemiology of the net blotch fungi and discusses the key challenges we are facing in managing the net blotches using both fungicide resistance and breeding strategies to achieve durable disease resistance in barley.

Net form of net blotch (NFNB), caused by Pyrenophora teres f. teres, is a major foliar disease of barley (Hordeum vulgare L.) worldwide that can cause grain yield and quality loss in susceptible varieties. Seed- and foliar-applied fungicides were evaluated in six field experiments infected with NFNB during 5 years, for suppression of NFNB severity and protection of grain yield and quality. Suppression of NFNB severity varied between treatments and experiments. Grain yield and quality improvements were recorded in two experiments. Foliar fungicide applications at stem elongation (Zadoks growth stage Z31) and flag leaf emergence (Z39) or ear emergence (Z55) significantly reduced NFNB severity, increased grain yield by up to 23%, and improved grain-quality measurements of retention, screenings and weight. The seed-applied fungicide fluxapyroxad provided significant reductions in NFNB severity, improvements in grain yield of up to 20%, and improved grain quality. Where NFNB was severe, none of the seed or foliar fungicide application strategies provided complete control of NFNB, indicating that more than two applications were necessary when conditions were favourable for disease development in susceptible varieties.

Scald, caused by Rhyncosporium commune, is a common foliar disease of barley in south eastern Australia, causing significant damage during cool, wet seasonal conditions. In this study, scald caused up to 30% (1.4 t/ha) grain yield loss, reduced grain plumpness and weight by up to 25% and 20% respectively and increased screenings by up to 6%. Seed, fertiliser and foliar applied fungicides reduced scald severity and provided improvements in both grain yield and quality. Dual foliar fungicide application of propiconazole at early stem elongation (Z31) and flag leaf emergence (Z39) was most effective in controlling scald and reducing grain yield and quality losses. The seed applied fungicide, fluxapyroxad was the most effective single application fungicide treatment. Varieties with host-plant resistance had less grain yield and quality loss than the very susceptible rated variety, however, these varied between seasons. This study demonstrated that an integrated disease management strategy is required for scald in barley that includes growing resistant varieties and timely fungicide applications.

Pyrenophora teres f. teres and P. teres f. maculata cause net form and spot form, respectively, of net blotch on barley (Hordeum vulgare). The two forms reproduce sexually, producing hybrids with genetic and pathogenic variability. Phenotypic identification of hybrids is challenging because lesions induced by hybrids on host plants resemble lesions induced by either P. teres f. teres or P. teres f. maculata. In this study, 12 sequence-specific polymerase chain reaction markers were developed based on expressed regions spread across the genome. The primers were validated using 210 P. teres isolates, 2 putative field hybrids (WAC10721 and SNB172), 50 laboratory-produced hybrids, and 7 isolates collected from barley grass (H. leporinum). The sequence-specific markers confirmed isolate WAC10721 as a hybrid. Only four P. teres f. teres markers amplified on DNA of barley grass isolates. Amplified fragment length polymorphism markers suggested that P. teres barley grass isolates are genetically different from P. teres barley isolates and that the second putative hybrid (SNB172) is a barley grass isolate. We developed a suite of markers which clearly distinguish the two forms of P. teres and enable unambiguous identification of hybrids.

QTL for tan spot resistance were mapped on wheat chromosomes 1A and 2A. Lines were developed with resistance alleles at these loci and at the tsn1 locus on chromosome 5B. These lines expressed significantly higher resistance than the parent with tsn1 only. Tan spot (syn. yellow spot and yellow leaf spot) caused by Pyrenophora tritici-repentis is an important foliar disease of wheat in Australia. Few resistance genes have been mapped in Australian germplasm and only one, known as tsn1 located on chromosome 5B, is known in Australian breeding programs. This gene confers insensitivity to the fungal effector ToxA. The main aim of this study was to map novel resistance loci in two populations: Calingiri/Wyalkatchem, which is fixed for the ToxA-insensitivity allele tsn1, and IGW2574/Annuello, which is fixed for the ToxA-sensitivity allele Tsn1. A second aim was to combine new loci with tsn1 to develop lines with improved resistance. Tan spot severity was evaluated at various growth stages and in multiple environments. Symptom severity traits exhibited quantitative variation. The most significant quantitative trait loci (QTL) were detected on chromosomes 2A and 1A. The QTL on 2A explained up to 29.2% of the genotypic variation in the Calingiri/Wyalkatchem population with the resistance allele contributed by Wyalkatchem. The QTL on 1A explained up to 28.1% of the genotypic variation in the IGW2574/Annuello population with the resistance allele contributed by Annuello. The resistance alleles at both QTL were successfully combined with tsn1 to develop lines that express significantly better resistance at both seedling and adult plant stages than Calingiri which has tsn1 only.

Spot form of net blotch (SFNB), caused by Pyrenophora teres f. maculata caused up to 25 % (0.9 t/ha) grain yield loss to barley and significant reductions in grain quality parameters such as retention (13 %), screenings (5 %) and grain weight (6 %) in the Wimmera region of Victoria during 2005–11. Spot form of net blotch was suppressed by varying degrees between experiments, seasons, and crop growth stages when foliar fungicide (propiconazole) was applied. Of single applications, treatment at the stem elongation (Z31) or flag leaf (Z39) growth stages generally provided the greatest disease suppression. Single application at tillering (Z25) or ear emergence (Z55) were generally ineffective. Eight chemical seed treatments registered for use in barley were tested as potential low cost management options for SFNB. Four seed treatments reduced SFNB severity in the glasshouse, but none were effective in the field.

Yellow spot (syn. tan spot), caused by Pyrenophora tritici-repentis, is an important foliar disease of wheat in Australia that causes losses exceeding 50

Strategies for genetic enhancement of resistance to yellow spot and stagonospora nodorum blotch in wheat Manisha Shankar, Diane Mather, Michael Francki, Dorthe Jorgensen, Hossein Golzar, Ken Chalmers, Esther Walker, Grant Hollaway, Mark McLean, Stephen Neate and Rob Loughman Department of Agriculture and Food, Western Australia The University of Adelaide, South Australia Department of Primary Industries, Victoria Department of Agriculture, Fisheries and Forestry, Queensland

The responses of 95 barley lines and cultivars to spot form of net blotch (SFNB) caused by Pyrenophora teres f. maculata were analyzed as seedlings and adults in Australia and Canada. Cluster analyses revealed complex reaction responses. Only 2 lines (Esperance Orge 289 and TR3189) were resistant to all isolates at the seedling stage, whereas 15 lines and cultivars (81-82/033, Arimont, BYDV-018, CBSS97M00855T-B2-M1-Y1-M2-Y-1M-0Y, CI9776, Keel, Sloop, Torrens, TR326, VB0111, Yarra, VB0229, WI-2477, WI2553, and Wisconsin Pedigree) were resistant toward the two Canadian isolates and mixture of Australian isolates at the adult stages. In Australian field experiments, the effectiveness of SFNB resistance in three barley cultivars (Barque, Cowabbie, and Schooner) and one breeding line (VB9104) with a different source of resistance was tested. Barque, which possessed a resistance gene that provided complete resistance to SFNB, was the most effective and showed no effect on grain yield or quality in the presence of inoculum. Generally, cultivars with seedling or adult resistance had less disease and better grain quality than the susceptible control, Dash, but they were not as effective as Barque. A preliminary differential set of 19 barley lines and cultivars for P. teres f. maculata is proposed.

Surveys of incidence and severity of foliar diseases in a total of 127 barley (Hordeum vulgare) crops throughout Victoria were carried out during 2007 and 2008. In each crop, 100 tillers were assessed for disease symptoms on the top four leaves. Spot form of net blotch caused by Pyrenophora teres f. maculate had the highest incidence, being present in more than 90% of crops surveyed, with severity ranging from 0 to 42%. Scald caused by Rhynchosporium secalis had the second highest incidence, being found in 13 and 23% of crops in 2007 and 2008, respectively, with severity ranging from 0 to 16%. Leaf rust caused by Puccinia hordei was present in 13 and 18% of crops in 2007 and 2008, respectively, with severity of up to 3%. Powdery mildew caused by Erysiphe graminis was present in 11 and 9% of crops in 2007 and 2008, respectively, with severity below 0.1%. No other diseases, such as the net form of net blotch caused by P. teres f. teres were detected. The high incidence of spot form of net blotch, which can cause up to 44% grain yield loss, suggests that resistance traits need to be made a priority and targeted by barley breeding programs in Victoria for control of this important disease.

Spot form of net blotch (SFNB), caused by the fungus Pyrenophora teres f. maculata, was first described in Denmark in the 1960s and is now a prevalent foliar disease of barley in many countries. This disease should be controlled as a separate disease-causing organism from the net form of net blotch (NFNB), which is caused by P. teres f. teres. The increase in prevalence of SFNB is primarily due to stubble retention and cultivation of susceptible varieties, which have resulted in increased inoculum. Infected barley stubble is the primary inoculum source for SFNB, producing both asexual spores (conidia) and sexual spores (ascospores) from pseudothecia. Spot form of net blotch causes significant losses in grain yield and quality in situations where inoculum is present, susceptible varieties are cultivated, and where the climate is cool and moist. Cultivation of resistant varieties is the most cost-effective method for control of SFNB and more than 12 different resistance sources have been identified in barley germplasm and wild barley relatives. The resistance loci of 11 of these have been mapped. Control of SFNB can also be achieved with application of foliar fungicides, crop rotation, and stubble destruction.

Acollection of 253 synthetic hexaploid wheats ( SHWs) produced from 192 Aegilops tauschii accessions and 39 elite durum varieties were studied to identify, characterise, and evaluate potentially untapped diversity of disease resistance in wheat. The diseases for which resistance was sought included cereal cyst nematode (CCN), root lesion nematode (RLN), Stagonospora nodorum blotch (SNB), Septoria tritici blotch (STB), and the 3 rusts, leaf rust, stem rust, and stripe rust, all important diseases of bread wheat worldwide, which can severely reduce wheat yield and quality. The SHW sexhibited a wide spectrum of resistance to the 8 pathogens. The frequency of disease-resistant SHWs ranged from 1% for one species of RLN (Pratylenchus neglectus), 3% and 10% for Septoria nodorum leaf and glume blotch, 10% for seedling resistance to yellow leaf spot, 16% for CCN, 21% for the second species of RLN(Pratylenchus thornei), 73% for Septoria tritici blotch, and 15%, 40%, and 24% for leaf rust, stem rust, and stripe rust, respectively. Five SHWs, Aus26860, Aus30258, Aus30294, Aus30301, and Aus30304, exhibited high levels of resistance to CCN, YLP, STB, LR, and SR, while 56 SHWs showed resistance to either 3 or 4 diseases. The genetics of resistance to CCN in some of the SHWs revealed that some of the accessions carry the same CCN gene(s) against pathotype Ha13, while others may carry different resistance gene( s). Additional studies were carried out to understand the relationship between the resistances identified in SHW sand the ones already present in common wheat, in particular the resistance genes Cre1 and Cre3 against CCN. The use of perfect markers associated with Cre1 and Cre3 suggested that some SHWs may carry a new CCN resistance gene( s), which could be deployed in breeding programs to increase the diversity of available resistance. The identification of SHWs with resistance to a range of diseases provides an opportunity to generate genetic knowledge and resistant germplasm to be used in future variety development.

Variety selection and robust disease management plans are critical to minimising the impact of diseases in cereal crops. The Victorian Cereal Disease Guide provides the latest information on disease management and the disease resistant ratings for cereal crops.