Abstract: 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.

Abstract: 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.