Activity 10

In years to come, the challenge to agriculture is to increase food production while simultaneously reducing the use of inputs and toxic products as well as offering ecosystem benefits. Modern agriculture relies on high yields, supported by plant breeding, monoculture and intensive use of chemicals, which leads to crop and systems homogenization. When parameters like maturity, quality and plant height are uniform, harvest, commercialization and grain processing are easier. In recent decades, varietal monoculture has spread around the world and led to a decrease in genetic diversity in the field. This has significant implications like faster spread of diseases and pests which requires widespread use of synthetic pesticides with negative side-effects. Their use is proscribed in organic agriculture, thereby limiting those adverse effects. The promotion of biodiversity in agroecosystem advocated in organic farming can definitely increase sustainability, and a lot of effort has been put in research on the subject. Lately, research is increasingly demonstrating the added value of intraspecific genetic diversity for the improvement of ecosystem stability and function (Crutsinger et al., 2006 ; Schöb et al., 2015). Also, recent climate is hotter and more variable, precipitation patterns are changing and extreme weather events like droughts and flood are becoming more frequent due to climate change (Ouranos, 2015; Stott et al., 2015). For example, according to NASA’s global climate change website (NASA, 2017), both July 2017 and 2016 were the warmest Julys of the past 137 years. It is also observed that geographical distribution areas of specific diseases and pests expand while new ones appear, leading to higher pest and disease problems (INRA, 2015). Also, limited genetic diversity can adversely affect crops or specific cultivars some years, especially when facing disease episodes. A richer genetic pool allows a better resilience of cropping systems and adaptability under biotic and abiotic stresses.

In past decades, genetic diversity in the grain field has decreased mostly because of intensive use of varietal monoculture and because modern wheat varieties have a narrower genetic basis (Fu and Dong, 2015). An alternative to varietal monoculture is variety mixtures. Among other things, this system reduces pesticide use (De Valavieille-Pope et al., 2005), making it interesting for organic production. Many advantages are reported in the literature such as yield stability, a better performance under stressful conditions like insect damage and disease outbreaks, and a more efficient use of environmental resources (Campbell et al., 1991; Sapoukina et al., 2013; Tooker and Frank, 2012). This is of particular interest because it will increase wheat competitiveness through improvement in productivity, production stability and resilience when facing climate extremes.

One problem is that Eastern climate and diseases are very different from what exists elsewhere, with strong Fusarium Head Blight (FHB) pressure. Interestingly, lower levels of Fusarium mycotoxin has been reported in cereal grown under organic management when compared with conventional management (Bernhoft et al., 2010; Birzele et al., 2002; Edwards, 2009; Gottschalk et al., 2009; Meister, 2009). Reasons explaining the lower contamination have not yet been understood, but various farming practices differ between these system management and this has been proposed as an explanation (Bernhoft et al., 2010; Edwards, 2009). Eastern climate also offers unpredictable variations from year to year and have lots of leaf spot pathogens, stem diseases (take-all, eyespot), insects (midge and hessian fly), sometimes Barley Yellow Dwarf Virus (BYDV), plus the full array of rusts including yellow rust (Puccinia striiformis f.sp. tritici) which arrived in 2013 and became epidemic in parts of Quebec in 2017. The challenge will be to find components that behave well under Eastern conditions for all traits: agronomic, disease and quality traits. Those components can hardly be sought outside registered varieties, because most of the wheat in Canada is not adequate for FHB resistance in Quebec. We therefore plan to stick with registered Quebec varieties unless pre-registration lines offer obvious value.

This project will evaluate agronomic and baking qualities of wheat cultivars grown in mixtures, for their adaptation to organic management in Eastern Canada. We will select three well-known wheat varieties (one early-, one intermediate-, and one late-ripening variety) as controls to compare binary, three- and four-component mixtures. From the beginning to the third year, single varieties and mixtures will be evaluated in small plots of 3.5 m² with three replicates in a randomized complete block. From year three, bread-making tests will be carried-out by the industry partner on single varieties as well as on cultivar mixtures and plot size will be increased to 10 m². Experiments will be carried out in two regions, namely Centre-du-Québec and Montérégie. The final outcome of the project is to give Eastern farmers access to a range of variety mixtures adapted to organic agriculture and climatic conditions.

Bernhoft, A., Clasen, P.E., Kristoffersen, A.B., and Torp, M. 2010. Less Fusarium infestation and mycotoxin contamination in organic than in conventional cereals. Food additives and contaminants: Part A. 27: 842-852.

Birzele, B., Meier, A., Hindorf, H., Krämer, J., and Dehne, H. W. 2002. Epidemiology of Fusarium infection and deoxynivalenol content in winter wheat in the Rhineland, Germany. In Mycotoxins in Plant Disease. pages 667-673. Springer Netherlands.

Campbell, B.D., Grime, J.P., and Mackey, J.M.L. 1991. A trade-off between scale and precision in resource foraging. Oecologia. 87: 532-538.

Crutsinger, G.M., Collins, M.D., Fordyce, J.A., Gompert, Z., Nice, C.C., and Sanders, N.J. 2006. Plant genotypic diversity predicts community structure and governs an ecosystem process. Science, 313(5789): 966-968.

De Vallavieille-Pope, C., Belhaj Fraj, M., Mille, B., and Meynard, J.M. 2005. Les associations de variétés : accroître la biodiversité pour mieux maîtriser les maladies. Dossier de l’environnement de l’INRA no30. P. 101-109.

Edwards, S. G. 2009. Fusarium mycotoxin content of UK organic and conventional wheat. Food Additives and Contaminants. 26(4) : 496-506.

Fu, Y.B. and Dong, Y. 2015. Genetic Erosion Under Modern Plant Breeding: Case Studies in Canadian Crop Gene Pools. In Ahuja, M.R. and Jain, S.M. (eds.). Genetic Diversity and Erosion in Plants. Springer. Chapter 4. pp. 89-104.

Gottschalk, C., Barthel, J., Engelhardt, G., Bauer, J., and Meyer, K. 2009. Simultaneous determination of type A, B and D trichothecenes and their occurrence in cereals and cereal products. Food additives and contaminants. 26(9): 1273-1289.

INRA (Institut National de la Recherche Agronomique). 2015. Le climat change, la nature et l’agriculture aussi! 25 p.

Meister, U. 2009. Fusarium toxins in cereals of integrated and organic cultivation from the Federal State of Brandenburg (Germany) harvested in the years 2000–2007. Mycotoxin research. 25(3): 133.

NASA. 2017. July 2017 equaled record July 2016 [online]. Available at https://climate.nasa.gov/news/2618/july-2017-equaled-record-july-2016/. Accessed August 29^th 2017.

Ouranos. 2015. Vers l’adaptation. Synthèse des connaissances sur les changements climatiques au Québec. Édition 2015. Montréal, Québec. Ouranos. 415 p.

Sapoukhina, N., Paillard, S., Dedryver, F., and de Vallavieille-Pope, C. 2013. Quantitative plant resistance in cultivar mixtures: wheat yellow rust as a modeling case study. New Phytologist.  200: 888-897.

Schöb, C., Kerle, S., Karley, A. J., Morcillo, L., Pakeman, R. J., Newton, A. C., and Brooker, R. W. (2015). Intraspecific genetic diversity and composition modify species‐level diversity–productivity relationships. New Phytologist. 205(2): 720-730.

Stott, P.A., Christidis, N., Otto, F.E.L., Sun, Y., Vanderlinden, J‐P., Van Oldenborgh, G.J., Vautard, R., Von Storch, H., Walton, P., Yiou, P.,  and Zwiers, F.W. 2016. Wiley interdisciplinary reviews: Climate Change. 7 (1): 23-41.

Tooker, J.F. and Frank, S.D. 2012. Genotypically diverse cultivar mixtures for insect pest management and increased crop yields. Journal of applied Ecology. 49: 974-985.

Varietal blends are the subject of abundant literature and are often presented as a promising agroecological practice. Despite their low level of adoption by agricultural producers, it is a practice that would benefit the whole sector, as it promotes system resilience by maintaining natural genetic diversity. With climate change, agroecosystems need to be better designed to cope with stress and adapt to change, additionally, the design of resilient food systems is in the best interest to all...

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Organic Science Canada- Spring 2023 (Page 6)