Mike Sissons

Fusarium crown rot (FCR), caused by the fungal pathogen Fusarium pseudograminearum (Fp), is a major constraint to cereal production worldwide. The pathogen restricts the movement of solutes within the plant due to mycelial colonisation of vascular tissue. Yield loss and quality downgrades are exacerbated by this disease under water stress conditions. Plant root systems are adaptive and can alter their architecture to optimise production in response to changes in environment and plant health. This plasticity of root systems typically favours resource acquisition of primarily water and nutrients. This study examined the impact of FCR on the root system architecture of multiple commercial bread and durum wheat varieties. Root system growth was recorded in-crop in large transparent rhizoboxes allowing visualization of root architecture over time. Furthermore, electrical resistivity tomography was used to quantify spatial root activity vertically down the soil profile. Results demonstrated a significant reduction in the total root length and network area with the inoculation of FCR. Electrical resistivity measurements indicated that the spatial pattern of water use for each cultivar was influenced differently from infection with FCR over the growing season. Specifically temporal water use can be correlated with FCR tolerance of the varieties marking this investigation the first to link root architecture and water use as tolerance mechanisms to FCR infection. This research has implications for more targeted selection of FCR tolerance characteristics in breeding programs along with improved specific varietal management in-crop.

Reserve starch, the main component of durum wheat semolina, is constituted of two glucan homopolymers (amylose and amylopectin) that differ in their chemical structure. Amylose is mainly a linear structure formed of α-1,4-linked glucose units, with a lower polymerization degree, whereas amylopectin is a highly branched structure of α-1,4-chains linked by α-1,6-bonds. Variation of the amylose/amylopectin ratio has a profound effect on the starch properties which may impact the wheat technological and nutritional characteristics and their possible use in the food and non-food sector. In this work a set of genotypes, with a range of amylose from 14.9 to 57.8%, derived from the durum wheat cv. Svevo was characterised at biochemical and rheological level and used to produce pasta to better understand the role of amylose content in a common genetic background. A negative correlation was observed between amylose content and semolina swelling power, starch peak viscosity, and pasta stickiness. A worsening of the firmness was observed in the low amylose pasta compared to the control (cv. Svevo), whereas no difference was highlighted in the high amylose samples. The resistant starch was higher in the high amylose (HA) pasta compared to the control and low amylose (LA) pasta. Noteworthy, the extent of starch digestion was reduced in the HA pasta while the LA genotypes offered a higher starch digestion, suggesting other possible applications.

Reserve starch, the main component of durum wheat semolina, is constituted by two glucan homopolymers (amylose and amylopectin) that differ in their chemical structure. Amylose is mainly a linear structure formed of α-1,4 linked glucose units, with a lower polymerization degree, whereas amylopectin is a highly branched structure of α-1,4 chains linked by α-1,6 bonds. Variation of the amylose/amylopectin ratio has a profound effect on the starch properties which may impact wheat technological and nutritional characteristics and their possible use in the food and non-food sector. Therefore, some breeding programs were focused on the production of high (HA) and low amylose (LA) genotypes using transgenic and conventional strategies. A great interest was aroused by new genotypes enriched in amylose for their beneficial effects for human health in the prevention of non-communicable diseases. Differently the low-amylose genotypes find applications in different industrial sectors (i.e. frozen and baby foods; starch-based sweeteners and industrial alcohol) for their unique properties. In this work a set of genotypes, with a range of amylose from 14.9 to 57.8%, derived from the durum wheat cv. Svevo was characterized at biochemical and rheological level and used for the production of pasta. A negative correlation was observed between amylose content and semolina swelling power, starch peak viscosity and pasta stickiness. A worsening of the firmness was observed in the low amylose pasta compared to the control (cv. Svevo), whereas no difference was highlighted in the high amylose samples. The resistant starch was higher in the HA pasta compared to the control and LA pasta. Noteworthy, the extent of starch digestion was reduced in the high amylose pasta while the low amylose genotypes offered a higher starch digestion, suggesting other possible applications.

Context The cereal disease Fusarium crown rot (FCR), caused by the fungal pathogen Fusarium pseudograminearum, is a worldwide major constraint to winter cereal production, especially in Australia’s northern grain region of New South Wales and Queensland. Aims Detection of the disease is labour-intensive and often not spatially quantifiable; hence, the aim of this study was to provide methods for in-crop FCR detection on a broadacre scale. Methods A replicated field experiment across three locations in northern New South Wales explored the use of thermal and multispectral imagery and hyperspectral reflectance data for the spatial detection of FCR in three bread wheat (Triticum aestivum L.) and three durum wheat (T. durum Desf.) varieties in the presence and absence of inoculation with F. pseudograminearum. Key results Canopy temperature was 0.30–0.90°C higher in two-thirds of field sites inoculated with the pathogen during early wheat growth in a slightly wetter than normal season. Some multispectral indices including normalised difference red edge, normalised difference vegetation index, near infrared and red edge also demonstrated the ability to identify inoculated versus uninoculated treatments as early as the first node stage (GS31). Conclusions Although positive identification was achieved with remote detection, environmental conditions (i.e. soil-water availability and ambient temperature) and physiological maturity influenced the accuracy of the technology for detecting FCR infection, particularly in wetter early-season conditions. Implications Early spatial detection of FCR infection on a broadacre scale could allow producers to manage this disease spatially through better agronomic decisions.

In Australia, adoption of reduced tillage and stubble retention cropping systems by growers to conserve soil moisture has seen an increase in the prevalence of the disease Fusarium crown rot (FCR) caused by the stubble-borne fungal pathogen Fusarium pseudograminearum. Durum wheat is particularly susceptible to FCR, exhibiting significant yield and quality losses in the presence of infection. Increasing rates of nitrogen (N) application at sowing exacerbates FCR. However, to achieve the desired grain protein and quality suited to pasta manufacturing, N application is necessary, and this creates a dilemma for growers. The purpose of this study was to investigate the effects of FCR infection in the presence of different N fertiliser application rates in durum wheat varieties on the yield and technological quality. Two durum varieties were evaluated at the same location over two seasons (2020 and 2021). These seasons were characterised by being wetter than normal and showed different responses to FCR and N application. Three rates of FCR inoculation and five rates of N fertilizer were applied (varying according to season) at sowing. In general, the 2021 season showed better responses to applied N regarding the yield and technological properties, with no impact from FCR. The FCR inoculation, while resulting in significant infections in 2020 (15–36-fold increase) and in 2021 (~45-fold increase), had no impacts on the yield or grain quality in 2021, while in 2020, the yield was reduced (24.9%), with variable effects on the technological properties. The 2021 season showed much more responses to applied N (grain protein increased by ~24%). Jandaroi was found to maintain its kernel vitreosity at all protein levels (mean of 88.5%), obtaining the premium grade, while DBA Lillaroi did not (mean vitreosity of 76.6%) and could be downgraded if N application was insufficient. However, higher N application rates needed to achieve more than 12% protein lead to a reduction in dough strength, with Jandaroi maintaining its dough strength much better (2.7% reduction in the gluten index) than DBA Lillaroi (18.2% reduction in the gluten index). This was related to the lower glutenin/gliadin (Gli/Glu) ratio in response to applied N at sowing in Jandaroi, which helped retain kernels with a high vitreousness. This suggests genetics plays an important role in a genotype’s response to N fertilisation and should be considered when selecting a genotype where higher premium grades are desirable.

In Australia adoption of reduced tillage and stubble retention cropping systems to conserve soil moisture by growers has seen an increase in the prevalence of the disease Fusarium crown rot (FCR) caused by the stubble-borne fungal pathogen Fusarium pseudograminearum. Durum wheat is particularly susceptible to FCR expressing significant yield and quality losses in the presence of infection. Increasing rates of nitrogen (N) application at sowing exacerbates FCR. However, to achieve the desired grain protein and quality suited to pasta manufacture, N application is necessary and this creates a dilemma for growers. The purpose of this study was to investigate the effects of FCR infection in the presence of different N fertiliser application rates in durum wheat varieties on yield and technological quality. Two durum varieties were evaluated at the same location over two seasons (2020 and 2021). These seasons were characterised by being wetter than normal and showed different responses to FCR and N application. In general, the 2021 season showed better responses to applied N with no impact of FCR. The FCR inoculation while it resulted in significant infection, it had no impacts on yield or grain quality in 2021 while in 2020 yield was reduced and only gluten index was reduced. Jandaroi was found to hold its kernel vitreosity at all protein levels obtaining the premium grade while DBA Lillaroi did not and would suffer downgrade if N application was insufficient. However, higher N application rates needed to achieve 12% + protein saw a reduction in dough strength with Jandaroi holding its dough strength much better than DBA Lillaroi. This was related to the lower glutenin/gliadin (Gli/Glu) ratio in response to applied N at sowing in Jandaroi which helped retain kernels with high vitreousness. This suggests genetics plays an important role in a genotype response to N fertilisation and should be considered when selecting a variety where higher premium grades are desirable.

Background and Objectives: While there are a few studies examining the impact of isolated starch A and B granule preparations on cereal end product quality, there is limited information about the effect of genotypic variation in B granule content in starch on pasta technological properties and pasta in vitro starch digestion. Crosses were made between a durum variety Yallaroi and a low and high B‐granule dicoccoides accession and the resulting population evaluated in field trials for starch B‐granule content (S‐BG) and selections made for more detailed analysis.Findings: Genotypes were grouped based on semolina B granule contents of 24.5%−26.7%, 31.7%−37.1%, and 43.9%−45.1% for analysis purposes. Preliminary field data indicated three “43.9−45.1%” B‐granule genotypes had lower grain and test weight and one of these, 156,224*2, a very high semolina Buhler mill yield. Pasta made from the genotypes produced acceptable pasta but there was no association between S‐BG and pasta properties. To overcome protein composition differences between genotypes, starch was isolated and reconstituted flours and pasta prepared. Starch from the same “43.9−45.1%” group all showed RVA profiles with lower final viscosities and setback and displayed higher gelatinization onset and peak temperatures than the “24.5−26.7%” group. Pasta made from reconstituted flours showed similar pasta quality and in vitro starch digestion properties.Conclusions: The data suggests no relationship between percentage of B‐granules and both pasta quality and starch digestion for the range and populations studied (S‐BG, 22%−44%).Significance and Novelty: This information provides new insights into the role varying S‐BG content in pasta cooking properties, texture and nutritional characteristics and could provide some direction to breeders to consider breeding for very low or very high B‐granule content.

The cereal disease Fusarium crown rot (FCR), caused by the fungal pathogen Fusarium pseudograminearum (Fp), is a major constraint to cereal production worldwide. Nitrogen (N) fertilizer is estimated to be approximately 30% of the input costs for grain growers in Australia and is the primary driver of yield and grain protein levels. When targeting high yield and protein, generous nitrogen fertilizer applications are thought to result in large biomass production, which exacerbates FCR severity, reducing grain yield and quality. This research was undertaken to investigate the effect of temporal N availability in high-protein bread and durum wheat varieties on FCR severity. Laboratory and controlled environment experiments assessed the relationship between FCR and N at a mechanistic and plant level. An in vitro study demonstrated an increase in Fp mycelial growth under increased N availability, especially when N was supplied as urea compared with ammonium nitrate. Similarly, under controlled environmental conditions, increased soil N availability promoted FCR severity within infected plants. Stem N transfer efficiency was significantly decreased under FCR infection in both bread and durum wheat varieties by 4.5% and 10.2%, respectively. This new research demonstrates that FCR not only decreases yield and grain quality but appears to have previously unrecognised detrimental impacts on nitrogen-use efficiency in wheat. This indicates that the current impact of losses from FCR may also decrease N-use inefficiencies, as well as yield and quality penalties. An improved understanding of the interactions and restrictions of FCR infection may allow growers to better manage the disease through manipulation of the soil’s temporal N availability.