Search

Stripe (yellow) rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is emerging as a serious threat to wheat (Triticum aestivum L.) production in many regions of North America. Genetic resistance to stripe rust is typically conditioned by the products of resistance genes that detect pathogen-associated molecular patterns and initiate a cascade of signalling events, culminating in the generation of reactive oxygen species (ROS) and a hypersensitive response (HR) that eventually suppress the pathogen. Complete resistance with no symptoms (immunity response) has also been observed, but less frequently, in certain Pst-wheat interactions. However, such HR-independent resistance responses to Pst have not been well studied. Here we report that the Pst-resistant near isogenic line Avocet-Yr15 (carrying the Yr15 resistance gene) exhibited an immunity response to an isolate of Pst collected in Elora, Ontario, while the Avocet-S line (lacking Yr15) was highly susceptible to the same isolate. In particular, histochemical assays of defence-associated ROS generation and HR were negative during the early stages of the interaction between Pst and the resistant Avocet-Yr15. Microscopic analysis indicated that the pathogen was not able to penetrate the stomata of Avocet-Yr15. Moreover, RNA-sequencing of the immunity response of Avocet-Yr15 to Pst highlighted the activation of a global anti-oxidative-stress response consisting of genes involved in the maintenance of cell viability, redox homoeostasis and photosynthesis. These results provide insights into the molecular mechanisms controlling the immunity response to stripe rust of wheat. [ABSTRACT FROM AUTHOR]

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a major disease of wheat (Triticum aestivum) in Ontario, which can cause 20% yield loss. The development of resistant commercial wheat cultivars is the most economical means of controlling this disease, but only if the resistance genes used are incompatible with the virulence phenotypes present in the pathogen population. The virulence structure of Bgt in Ontario was examined in 2018 and 2019. Of the 42 single colony isolates collected in Ontario greenhouses and commercial fields, 40 virulence phenotypes, assigned VP1 to VP40, were identified on a set of 24 single-gene differential genotypes. Of the 24 resistance genes possessed by the differential genotypes, eight genes including Pm1a, Pm1b, Pm1c, Pm12, Pm16, Pm21, Pm37, and MlAG12 were effective against all of the Bgt isolates. Four genes including Pm3d, Pm29, Pm34, and NCAG13 were mostly effective with resistance reactions to more than 80% of the isolates. There were no significant differences in numbers of virulence genes per isolate between the two years, or between the greenhouse and field origins. The virulence frequencies of Bgt isolates for these effective and mostly effective genes were also not significantly affected by the year of collection and their origins, suggesting that the Bgt population is relatively stable. The effective genes identified in this study may be deployed singly or used for gene pyramiding in wheat breeding programs for developing powdery mildew-resistant cultivars in Ontario. [ABSTRACT FROM AUTHOR]

Fusarium spp. associated with fusarium head blight (FHB) on cereals in Ontario was monitored in this study. Nine species were recovered from 24 300 putatively infected kernels collected from 486 affected spring wheat fields from 2001 to 2017, 11 species from 13 250 kernels from 265 barley fields from 2005 to 2017, and nine species from 8800 kernels from 176 oat fields from 2008 to 2017. Fusarium avenaceum, F. equiseti, F. graminearum, F. poae and F. sporotrichioides were the most commonly isolated species, occurring in 23–66% of the infected fields and 1.3–27.0% of the infected kernels. In spring wheat, F. graminearum was predominant, occurring in 88% of fields and in 60.4% of kernels, and represented 90% of the pathogen population. In barley, F. poae and F. graminearum were equally dominant, occurring in 77% and 64% of fields, 17.6% and 17.0% of kernels, and represented 42% and 40% of the pathogen population, respectively. In oat, F. poae was predominant, occurring in 93% of fields and 23.5% of kernels, and represented 68% of the pathogen population. Growth seasons characterized as an FHB epidemic occurred in 11 of 17 years surveyed in spring wheat, 3 of 13 years surveyed in barley, and no epidemic years were observed over the 10-year period in oat. There were no significant differences in frequency of isolation of the Fusarium species, except for F. graminearum which increased by 60% in wheat and by 210% in barley in the FHB epidemic years compared with the non-epidemic years, suggesting that F. graminearum was responsible for the FHB epidemics in Ontario. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study evaluating the antioxidant properties and bioactive components of hard and soft wheat varieties cultivated in Ontario. The results show that whole-grain wheat has the ability to resist oxidation of key important biomolecules. Key components of wheat that bring health benefits include dietary fibers, protein, minerals and phytochemicals. Information on the wheat's antioxidant capacity and solubility in phenolic compounds is discussed.

The article examined the influence of three inoculum sources on the development of fusarium head blight (FHB) and the deoxynivalenol content (DON) in spring wheat in a disease nursery in Ottawa, Ontario. The progress of FHB was monitored by visually estimating disease severity during each growing season and its symptoms were also rated, at a critical development stage, as critical-time disease severity, percentage of infected spikelets and FHB index.