Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is one of the most destructive leaf spot diseases of wheat in Canada. Several races of the fungus are known to occur. Wheat growers have adopted fungicides to manage tan spot; however, intensive spraying may lead to development of reduced sensitivity to fungicides in the pathogen. In this study, 62 Ptr isolates were collected from across Saskatchewan and Alberta and characterized to race on a wheat differential set, with confirmation of race designations by polymerase chain reaction. This same set of isolates, and 27 isolates from an earlier study, were also evaluated for sensitivity to propiconazole and pyraclostrobin fungicides by determining the effective concentration of each needed to inhibit radial growth and conidiospore germination by 50%. Races 1 and 2 were predominant in western Canada, with 57% of isolates classified as race 1 and 40% as race 2. In Alberta, race 1 was most common (76%), while in Saskatchewan, it was race 2 (57%). Two of 26 isolates were classified as race 3, which was detected only in Saskatchewan in 2013. There was no evidence of reduced sensitivity of either fungicide in the Ptr isolates examined. This study provides a baseline for Ptr sensitivity to propiconazole and pyraclostrobin to which future collections of the pathogen may be compared.
Precision agriculture technology allows growers to selectively apply inputs to different management units within a single field. A 4‐yr study consisting of a split‐split block experiment was conducted in the northern prairies to determine the effects of foliar fungicide (FU) and N fertilizer application to slope (SL) position based management units across a hummocky landscape on leaf spot and root diseases, biomass and seed yield, and seed quality of wheat ( Triticum aestivum L.). Fertilizer rates (0, 40, 80, and 120 kg N ha −1 ) were applied in strips across two SL positions (upper and lower) as main plots with FU application (treated and untreated) as subplots. Leaf spot diseases were consistently more severe on the upper than lower SL and reduced by FU treatment but varied inconsistently with changes in N rate. Biomass and seed yield in the two dry years were greater on the lower than upper SL. They were increased by FU treatment in 3 of 4 yr and N rate in 1 yr. Thousand‐kernel weight (TKW) and grain test weight (TW) were usually greater on the upper than lower SL, and TKW was increased by FU application in 2 yr. Protein content usually increased with increasing N rate, but the effect of SL and FU varied among years. The paucity of interactions among treatment factors indicated that selective application of FU and N fertilizer to SL position based management units for improvement of yield and seed quality was not warranted.
CDC Plava oilseed flax (Linum usitatissimum L.), registered in 2015 by the Crop Development Centre, University of Saskatchewan, Saskatoon, SK, Canada, is targeted to the shorter growing season and the Dark Brown, Black, Grey, and Dark Grey soil zones of the northern prairies. This cultivar has a high seed yield (106%) compared with cultivar CDC Bethune and a medium maturity rating equal to Prairie Thunder. It has medium oil content (47.0%), α-linolenic acid content (57.8%), seed size (6.1 g 1000-seed weight), and good lodging resistance. It is resistant to North American races of rust caused by Melampsora lini (Ehrenb.) Thüm. and moderately resistant to wilt caused by Fusarium oxysporum Schltdl. f. sp. lini (Bolley) W.C. Snyder & H.N. Hansen.
Net blotch, caused by Pyrenophora teres, is an economically important disease of barley. The pathogen has two morphologically similar but genetically distinct forms: P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which cause net form net blotch (NFNB) and spot form net blotch (SFNB), respectively. The virulence of a collection of 39 Ptt and 27 Ptm isolates collected from western Canada was evaluated by inoculating these isolates onto sets of barley differential hosts. One week following inoculation, the second and third leaves of each plant were rated for disease severity on scales of 1–10 (for Ptt) or 1–9 (for Ptm). Plants rated <5 and ≥5 were scored as resistant and susceptible to Ptt, respectively, while plants rated 1–3 and >3 were scored as resistant and susceptible to Ptm. The experiment was repeated. Cluster analysis revealed 16 and 13 distinct pathotype groups, respectively, among the 39 and 27 representative Ptt and Ptm isolates. The barley differentials CI 5791 and CI 9820 were resistant to all isolates of Ptt except one, whilst the differential CI 9214 was resistant to all isolates of Ptm except two. Therefore, the differential lines CI 5791 and CI 9820, for Ptt, and CI 9214, for Ptm, can still be considered as potentially useful sources of resistance for Canadian barley breeding programmes.
The great majority of modern agro-ecosystems comprise rotations of a small number of crop species where each year’s crop is a genetically uniform monoculture. The narrow genetic basis for disease resistance in modern cultivars increases the potential for pathogens to overcome this resistance and attack a large number of plants at a similar state of development. In this chapter, we present a number of strategies for limiting foliar disease development in wheat and barley. We discuss how crop rotations with non-cereal species can substantially reduce inoculum sources for residue-borne cereal leaf diseases. Further strategies, such as intercropping, gene deployment and conversation tillage, are then presented, with discussion of the effectiveness of each strategy against particular foliar diseases. It is concluded that there is potential for residue-borne cereal leaf diseases to be managed under conservation tillage via crop rotation, fungicide application and careful choice of variety.
Harker, K. N., O’Donovan, J. T., Turkington, T. K., Blackshaw, R. E., Lupwayi, N. Z., Smith, E. G., Johnson, E. N., Gan, Y., Kutcher, H. R., Dosdall, L. M. and Peng, G. 2015. Canola rotation frequency impacts canola yield and associated pest species. Can. J. Plant Sci. 95: 9–20. Canola (Brassica napus L.) production has been steadily increasing in western Canada. Here we determine the effect of canola rotation frequency on canola seed yield, quality and associated pest species. From 2008 to 2013, direct-seeded experiments involving continuous canola and all rotation phases of wheat (Triticum aestivum L.) and canola or field pea (Pisum sativum L.), barley (Hordeum vulgare L.) and canola were conducted at five western Canada locations. Fertilizers, herbicides, and insecticides were applied as required for optimal production of all crops. Canola rotation frequency did not influence canola oil or protein concentration or the level of major (composition>1%) seed oil fatty acids. High canola yields were associated with sites that experienced cooler temperatures with adequate and relatively uniform precipitation events. For each annual increase in the number of crops between canola, canola yield increased from 0.20 to 0.36 Mg ha −1 . Although total weed density was not strongly associated with canola yield, decreased blackleg disease and root maggot damage were associated with greater canola yields as rotational diversity increased. Long-term sustainable canola production will increase with cropping system diversity.
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