Petronaitis, Toni

Flavel, Richard

Backhouse, David

Simpfendorfer, Steven

Brodie, Graham

2022-08-10

<p>Stubble-borne diseases are a major constraint to wheat and barley production in the northern grain region (NGR) of Australia, with associated incidence and severity rising due to increased adoption of conservation agriculture. The fungal pathogens that cause these diseases can colonise retained cereal stubble (saprotrophic colonisation), which may further increase inoculum levels after harvest. As such, we set out to understand what drives saprotrophic colonisation of the pathogens which cause Fusarium crown rot (<em>Fusarium pseudograminearum</em>), common root rot (<em>Bipolaris sorokiniana</em>) and yellow leaf spot (<em>Pyrenophora tritici-repentis</em>) and investigate new field management options for reducing inoculum carry-over into subsequent seasons. This was done using a controlled relative humidity (RH) experiment, a glasshouse experiment, two three-year field experiments, and two laboratory-based microwave radiation experiments. In the RH experiment, <em>Fusarium pseudograminearum</em> showed an increased relative saprotrophic fitness, colonising 20 to 42% more stubble length over a 7-day period at 100% RH compared with <em>B. sorokiniana</em> and <em>P. tritici-repentis</em>, respectively. Saprotrophic colonisation by all three pathogens in sterile post-harvest stubble was also significantly faster under higher moisture conditions of 97.5 % RH and above and was largely unaffected by cereal crop type or level of genetic resistance. Further glasshouse experimentation with <em>F. pseudograminearum</em> confirmed that crop selection may limit pathogen colonisation in-crop (in oat) but not saprotrophic colonisation post-harvest. After plant senescence, <em>F. pseudograminearum</em> colonised up to 23.5 cm higher in the main tiller of highly resistant wheat germplasm LRC2012-122 compared with the most susceptible wheat cv. Kittyhawk. These findings confirmed that crop selection remains a useful tool to limit Fusarium crown rot symptoms but cannot be used to manage saprotrophic colonisation in post-harvest stubble. Two new management strategies were therefore investigated to control or reduce inoculum in post-harvest stubble. Lowering the cereal harvest height of a durum wheat crop infected with <em>F. pseudograminearum</em> effectively restricted saprotrophic colonisation of post-harvest stubble by 61 to 70% at two field sites in the NGR. In the shorter-term, harvest height modification could therefore be developed as a useful integrated disease management strategy to improve stubble-borne disease management in the NGR. In the longer-term, using microwave radiation to kill stubble-borne pathogens appears promising to remove pathogens from cereal stubble in situ whilst retaining the associated benefits of stubble retention. For instance, reduction of pathogens <em>B. sorokiniana, F. pseudograminearum</em> and <em>F. cerealis</em> in solution required 150 to 300 Jg^-1 of microwave energy to eliminate 99% of pathogen populations. Heating of wheat and barley stubble using microwave radiation also appears effective, particularly at lower microwave frequencies (_MHz) and higher stubble moisture (30-100% moisture by weight). These findings have been important to improve our understanding of saprotrophic phase of the stubble-borne disease cycle whilst also offering several new directions for stubble-borne disease management. Ultimately, future management strategies need to consider the role of inoculum production in both the pathogenic and saprotrophic phases to better control stubble-borne cereal diseases in the NGR.</p> <p>Datasets included:<ul><li>Chapter 2 data set - Colonisation of sterile stubble (1 durum wheat, 1 oat, 2 wheat and 2 barley varieties) inoculated with 6 cereal pathogens (2 isolates each of <em>Fusarium pseudograminearum, Fusarium cerealis</em> and <em>Bipolaris sorokiniana</em>) and incubated at 90, 92.5, 95, 97.5 and 100% relative humidity.</li><li>Chapter 3 data set - Stem colonisation, disease symptoms and pathogen biomass of cereal cultivars (1 durum wheat, 1 oat, 5 wheat and 3 barley) inoculated with <em>Fusarium pseudograminearum</em> and assessed at 4 sampling times (GS32, GS61, GS90 and post-harvest).</li><li>Chapter 4 data set - Field experiments (Breeza site) - Data collected during 3-year field experiments to assess crown rot inoculum at different harvest heights and stubble management strategies using stubble from an infected durum crop through a chickpea break crop, with assessment of disease incidence and severity in a final wheat crop at Breeza, NSW across the 2019, 20 and 21 growing seasons.</li><li>Chapter 4 data set - Field experiments (Narrabri site) - Data collected during 3-year field experiments to assess crown rot inoculum at different harvest heights and stubble management strategies using stubble from an infected durum crop through a chickpea break crop, with assessment of disease incidence and severity in a final wheat crop at Narrabri, NSW across the 2019, 20 and 21 growing seasons.</li><li>Chapter 5 data set - Laboratory based microwave dose-response experiments on conidia of <em>B. sorokiniana</em> and macroconidia of <em>F. pseudograminearum</em> and <em>F. cerealis</em> whereby 10 ml spore solutions were microwaved for up to 10 seconds using a domestic 1100 W microwave oven. </li><li>bytes Chapter 6 data set - Dielectric properties of cereal stubble infected with <em>Bipolaris sorokiniana, Fusarium pseudograminearum</em> and <em>Pyrenophora teres</em> in the microwave frequency range - characterising stubble to explain differences in dielectric responses.</li><li>Chapter 6 data set - The dielectric properties of wheat and barley stubble with different pathogen loads (<em>Fusarium pseudograminearum, Bipolaris sorokiniana</em> and <em>Pyrenophora tritici-repentis</em>) were investigated at 10%, 15%, 30% and 100% moisture content using an open-ended coaxial probe in a spectral band covering three important industrial, scientific and medical (ISM) frequencies (915, 2450 and 5800 MHz)</li><li>Chapter 6 data set - Raw data output files for dielectric properties of cereal stubble infected with <em>Bipolaris sorokiniana, Fusarium pseudograminearum</em> and <em>Pyrenophora teres</em> in the microwave frequency range.

https://hdl.handle.net/1959.11/55581

University of New England

Progressing stubble-borne disease management of winter cereals in the northern grain region of Australia - Dataset

Dataset

Publication