Clubroot and the importance of canola in Canada

Abstract

Canola (Brassica napus L., B. rapa L. and B. juncea L.) produces one of the vegetable oils most beneficial for human health. Consequently, canola is a valuable crop for Canada. The canola industry in Canada is estimated at an annual average value of C$15.4 billion between 2007–08 and 2009–10. Farm cash receipts of canola were valued at C$8.9 billion in 2012. The value of this crop is now threatened by clubroot disease caused by Plasmodiophora brassicae (Woronin.), which has expanded dramatically since its discovery on canola in Alberta in 2003. Since this pathogen moves with infested soil from field to field, control can be very costly to farmers. Even with new control options such as pathogen resistance, the proactive management of clubroot will represent a challenge to the canola industry. Continued research into pathogen control is a necessity for the sustained success of the Canadian canola industry.

Résumé

Le canola (Brassica napus L., B. rapa L. et B. juncea L.) produit une des meilleures huiles végétales pour la santé humaine. En conséquence, le canola est une culture de grande valeur pour le Canada. De 2007–2008 à 2009–2010, au Canada, l’industrie du canola a été évaluée à 15.4 milliards de dollars canadiens en moyenne annuellement. En 2012, les recettes financières agricoles relatives au canola ont été estimées à 8.9 milliards de dollars canadiens. Par ailleurs, la valeur de cette culture est actuellement menacée par la hernie, causée par Plasmodiophora brassicae (Woronin), qui s’est répandue de façon spectaculaire depuis sa découverte en Alberta en 2003. Étant donné que cet agent pathogène est transmis de champ en champ par le sol contaminé, sa gestion peut être très coûteuse pour les producteurs. Même avec les nouveaux outils de lutte comme la résistance à l’agent pathogène, la gestion proactive de la hernie représente un défi pour l’industrie du canola. La recherche continue relative à la lutte contre cet agent pathogène est essentielle au succès soutenu de l’industrie canadienne du canola.

Keywords:

• Brassica napus
• Canada
• canola
• clubroot
• economic impact
• Plasmodiophora brassicae
• production values

Mots clés:

• Brassica napus
• Canada
• canola
• hernie
• Plasmodiophora brassicae
• répercussions économiques
• valeurs de production

Introduction

Canola was developed via conventional plant breeding techniques from genotypes of oilseed rape in the mid 1970s at the Universities of Manitoba and Saskatchewan by Drs Baldur Stephenson and Keith Downey, respectively, and is the name applied now to several Brassica species grown in Canada. Both oilseed rape and canola are members of the Brassicaceae family. Oilseed rape has a long history of use by humankind for industrial purposes but the oil and meal (presscake) contain antinutritional compounds which limit its use for human and livestock diets (Busch et al. 1994). Cultivars without these compounds were developed in Europe and North America. Stephenson and Downey were responsible for removing the antinutritional compounds – erucic acid, glucosinolates and excess seed chlorophyll – while retaining favourable agronomic characteristics that allow this crop to be widely adapted to the Canadian prairies. Canola quality cultivars of three Brassica species – Brassica napus L., Brassica rapa L., and Brassica juncea L. – are registered for production in Canada, although B. napus cultivars predominate.

Specifically, these cultivars must contain less than 2% erucic acid and lower than 30 μmol g⁻¹ glucosinolates to be designated as canola. In 1979, ‘Canola’ was trademarked to officially recognize this ‘made in Canada’ crop and ensure that cultivars which do not meet these quality standards are not marketed as ‘canola quality’. The U.S. Food and Drug Administration (FDA) granted canola oil ‘generally regarded as safe’ (GRAS) status as a dietary component in 1985 and this was a significant stimulus for the adoption of canola seed, oil and meal as globally traded products.

Canola oil is widely recognized for its contribution to human health and wellness based on its composition. Canola contains low levels of saturated fat (7%) along with safflower, the lowest of all values for vegetable oils. It also contains substantial amounts of monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs), including 61% oleic acid, 21% linoleic acid and 11% alpha-linolenic acid (ALA – a dietary essential omega-3 fat). Additionally, canola oil contains plant sterols (0.53–0.97%) and tocopherols (700–1200 ppm) (Przybylski et al. 2005; Gunstone 2011). These components contribute to cardiovascular health and are important for the prevention of cardiovascular maladies. For the treatment of existing cardiovascular disease, canola oil has been recommended for achieving daily omega-3 fat requirements of 1 g day⁻¹ (Kris-Etherton 1999; Gebauer et al. 2006). In 2006, the US FDA authorized the following qualified health claim for canola oil: ‘Limited and not conclusive scientific evidence suggests that eating about 1 tablespoons (19 grams) of canola oil daily may reduce the risk of coronary heart disease due to the unsaturated fat content in canola oil. To achieve this possible benefit, canola oil is to replace a similar amount of saturated fat and not increase the total number of calories you eat in a day.’ (Center for Food Safety and Applied Nutrition 2006).

In addition to cardioprotective effects, in vitro and in vivo animal data and human clinical data are emerging which provide evidence for the positive effect of canola oil on insulin responses and diabetes (West et al. 2005; Riserus 2008) and cancer biomarkers (Hooper et al. 2006; Cho et al. 2010). The evidence-based health benefits of canola oil have played an important role in differentiating canola oil from other vegetable oils in the market place and have contributed to consumer demand.

The majority of canola oil is currently utilized in dressings and salad oils, margarines and spreads and for cooking/frying in the home, restaurant and food services sectors. Canola meal or press cake (the residual seed material remaining after oil extraction) is an excellent source of vitamins B and E and is a protein source for the aquaculture and animal feed industries.

Canadian canola production

Canola production in Canada is concentrated in the Prairie Provinces of Alberta, Saskatchewan and Manitoba. There is also production in the Peace River region of northern British Columbia and in areas of Ontario and Quebec. In the Prairie Provinces, canola production has historically been most intensive in the black and dark brown soil zones, while production areas in the brown and grey wooded soil zones has been increasing in the past decade. Figure 1 illustrates the geographic distribution of canola production in Canada. Canola production in Canada is historically surpassed by oilseed rape production in the European Union (EU) in terms of total volume of seed produced.

Fig. 1. (Colour online) Geographic distribution of canola production in Canada (yellow areas).

Planted and harvested areas of canola in Canada have fluctuated historically, but since 2002 they have risen steadily from 3.6 million hectares harvested to a peak 8.6 million hectares harvested in 2012 (Fig. 2). During this period, canola production reflected the increase in harvested hectares, with the exception of 2012. This increase in production is reflected in the number of farmers growing canola. The 2011 census data indicate that there were 43 000 farmers in Canada growing canola.

Fig. 2. Harvested hectares and production of canola in Canada (1986–2012). Adapted from Statistics Canada, CANSIM Table 0001–0010.

In November 2012, Statistics Canada indicated that canola production in Canada for that year was 13.3 million tonnes, down 8.9% from the record 14.6 million tonnes in 2011 (Statistics Canada CANSIM table 001–0010). The yield average for Canada in 2012 was 1550 kg ha⁻¹, a 19.2% yield decrease when compared with the 1920 kg ha⁻¹ yield average in 2011 (Statistics Canada CANSIM table 001–0010). The highest average yield in Canada was 1980 kg ha⁻¹, recorded in 2009. To provide a historical perspective on canola yields in Canada, in 1992, the yield average was 1270 kg ha⁻¹. Canola production has been hindered by a number of factors in Canada during this period, including diseases such as clubroot.

In 2012, canola production fell in Saskatchewan and Alberta, as a result of lower yields compared with 2011. In Saskatchewan, the average canola yield was 1380 kg ha⁻¹, a 25.2% yield reduction compared with 2011. In Alberta, the average canola yield was 1880 kg ha⁻¹, which was 14.9% lower than 2011. In Manitoba, canola production increased 20.3% to 2.1 million tonnes. This followed a 21.2% decline in 2011 when farmers were unable to recover from early season flooding. The increase in 2012 was a result of a 30.5% gain in harvested area, to 1.5 million hectares, which surpassed the previous record of 1.3 million hectares in 2009. Average yields decreased, however, by 7.8% from 2011 to 1460 kg ha⁻¹.

Economics of canola in Canada

A breakdown of the canola value chain in Canada provides an indication of the contribution of the canola industry to the Canadian economy (Fig. 3). Canola oil processing is one of the most important value-added agribusinesses in Canada. An analysis of the canola value chain distinguishes between direct and indirect benefits (Fig. 4). Direct benefits are those economic, employment and wage effects that can be directly attributed to the canola value chain. Indirect effects are the economic, employment and wage impacts created by those industries that supply the canola value chain, or by individuals who work at the periphery of the sector.

Fig. 3. The canola value chain in Canada.

Fig. 4. (Colour online) Total annual economic impact of canola industry sectors in Canada (average 2007–2009 in Canadian dollars).

Farm production, which utilizes high value planting seed and a number of crop inputs to produce approximately 12 million tonnes of canola seed, directly contributed an annual average of C$5252 million to the Canadian economy between 2007/08 and 2009/10. Farm gate receipts from canola have risen since 2008 and in 2012 accounted for a quarter of the total crop receipts in Canada (Table 1). Farm gate cash receipts have surpassed wheat (Triticum aestivum L.), due to the profitability of canola to farming enterprises in western Canada.

Table 1. Farm cash receipts in Canada (2008–2012) in C$1000s.

Type of cash receipts	2008	2009	2010	2011	2012
Total farm cash receipts	$46 093 917	$44 599 139	$44 466 265	$49 964 197	$53 688 347
Total crops receipts	$23 023 963	$23 201 510	$22 405 532	$26 035 382	$29 261 973
Wheat, excluding durum	$3 564 477	$3 270 369	$2 519 854	$3 585 851	$4 178 249
Canola	$4 914 580	$5 107 129	$5 584 110	$7 668 664	$8 227 776

Source: Statistics Canada. CANSIM table 002–0001.

Canola oilseed processing utilizes a significant amount of the annual seed production, creating domestic economic value. Most of the value-added processing for other grains and oilseeds produced in Canada occurs in countries that import the crop. Canola seed crushing enhances the value of the seed through production of oil for the food and biodiesel sectors, and meal for use in the livestock sectors. The Canadian crushing sector contributed an annual average of C$430 million to the Canadian economy between 2007–2008 and 2009–10. There are currently 13 canola crushing facilities located in Canada with a capacity to crush 8 million tonnes of canola seed annually and one additional plant under construction in Camrose, Alberta. The domestic industry capacity has more than doubled since 2006. Currently, Canada has the capacity to process domestically over 50% of the canola crop that is grown, and the processing capacity is further expanding in 2013–2014. Canola seed yield losses due to biotic and abiotic factors have a significant impact on local economies.

Oil refining, which adds value to crude canola oil through refining and further processing for human consumption, added a further annual average of C$184 million of value directly to the Canadian economy in the same period. End uses of canola products, including the benefits to the dairy sector from canola meal and use of canola oil in the food processing industry, contribute an annual average of C$723 million to the Canadian economy.

Grain and product handling, which adds value to canola seed, meal and oil as they move from farm or crushing locations to ports for export or to domestic locations, directly contributed an annual average of C$526 million to the Canadian economy. Transportation of canola seed and products, which adds value through the movement of seed, meal and oil from production areas or areas of surplus and lower prices to deficit areas with higher prices, contributed an annual average of C$505 million to the Canadian economy. Employment, which represents the people who are directly employed in each of these sectors (including end uses) and the wages that they earn, contributed C$6.331 million in wages for approximately 116 000 jobs linked directly to the canola sector in Canada.

The canola seed that is not crushed and processed in Canada is exported globally. Canada also exports a significant amount of the oil and meal or pressed cake that is processed in Canada (Table 2). Japan has been a significant and stable canola seed buyer for the past decade and China is emerging as another substantial importer of Canadian canola seed (Fig. 5).

Fig. 5. Canadian canola seed exports by country of destination for the calendar years 2003–2012. Adapted from the Canadian International Merchandise Trade Database – Statistics Canada.

Table 2. Volume of Canadian canola seed, oil and meal exports (2002–2012) in 1000s of tonnes.

	Calendar year
Canola product	2003	2004	2005	2006	2007	2008	2009	2010	2011	2012
Canola seed	3242	3440	3797	5122	5014	6661	7630	7470	7890	8333
Canola oil	409	983	830	1044	1154	1361	1510	2175	2487	2664
Canola meal	1127	1539	1412	1529	1589	1893	1752	2472	3100	3447

Current demand for canola meal is strong given the limited world protein supply for animal feed. Canola and rapeseed meals are the second most widely traded protein ingredients in animal feed after soybean meal. As stated earlier, almost all of the demand for Canadian canola meal is from the US dairy industry. The USA imported approximately 98% of Canada’s 1.5 million tonnes of exported canola meal in 2006 and is still Canada’s major importer (Table 3).

Table 3. Total Canadian canola meal exports (1000s of tonnes) by destination country.

Importing country	Calendar year
	2006	2007	2008	2009	2010	2011	2012
China			1	33	825	586	303
European Union (27)		24	10	7	40	61	61
Indonesia		1		9	7		1
Mexico		9	35	161	153	65	66
South Korea					23
Taiwan	9	9	9	6	7	4	1
Thailand		1		41	18	22	42
USA	1505	1542	1837	1468	1347	2337	2879
Vietnam		1		26	47	15	57
Others	15	2	1		6	10	37
Total	1529	1589	1893	1752	2472	3100	3447

Source: Adapted from the Canadian International Merchandise Trade Database – Statistics Canada.

In a study prepared in 2011 in accordance with the Canola Market Access Plan through Agriculture and Agri-Food Canada's Agriflexiblity funding, utilizing data from three crop years (2007–08, 2008–09 and 2009–10), Canadian-grown canola contributes an average of $15.4 billion to the Canadian economy each year, including more than 228 000 Canadian jobs and $8.2 billion in wages when both direct and indirect economic effects are considered.

Clubroot and the canola industry

Clubroot, caused by Plasmodiophora brassicae (Woronin), was found for the first time in canola in western Canada in 2003 near Edmonton, Alberta (Tewari et al. 2005), and has continued to spread dramatically across Alberta and into Saskatchewan (Dokken-Bouchard et al. 2010) and Manitoba (Manitoba Agriculture et al. 2013). The expansion of clubroot disease has surprised the canola industry, which initially believed that this soilborne disease would remain a local problem for growers near Edmonton. At its most severe, clubroot can completely devastate a canola field, killing all the plants, and reducing yield to near zero (Strelkov et al. 2007). However, this level of severity is rare, and significant economic losses occur only infrequently (Murray Hartman, personal communication).

There are no reliable estimates for chronic yield and economic losses because field infestations found by local municipal agricultural staff in Alberta are generally reported as a presence or absence, with few efforts made to quantify the amount and severity of disease across a field. In recent years, cultivars with resistance to P. brassicae have been developed by life science/seed companies and the availability of this seed and its adoption by farmers reduces the risk of yield losses, even in fields that have a history of severe levels of infestation. Few growers will knowingly plant susceptible cultivars in fields with anything greater than trace infestations.

Long-term stewardship or management of clubroot still poses a number of challenges for canola growers, even with the introduction of resistant cultivars. The near impossibility for the removal of P. brassicae inoculum from an infested field makes this pathogen a difficult one for canola growers to control. Essentially, once this disease is established in a field, it effectively is there for many years, possibly decades. This persistence leads to another difficulty for canola growers – how to prevent the pathogen from spreading. Since P. brassicae resting spores travel with infested soil, farmers in areas with clubroot have been looking for solutions which limit the movement of soil from one field to another. This is very difficult to achieve since soil movement is a normal farming practice. Field equipment is believed to be the primary method of pathogen spread (Strelkov et al. 2011). Recommendations to sanitise equipment and personnel between canola fields are promoted heavily in the canola industry (Jurke et al. 2011), but the uptake of these recommendations has been slow due to the time investment needed to completely disinfect a large piece of equipment. The trade-off for canola growers has been to examine this immediate cost of sanitation versus the potential costs due to yield loss. Managing clubroot on a farm adds additional complexity for canola growers, in a time when farms are increasing in size and trying to simplify operations and therefore maximize business efficiency.

Multiple pathotypes of P. brassicae have been identified on canola in Alberta (Strelkov et al. 2006; Xue et al. 2008). This biological diversity will pose challenges for canola growers for many years, since the potential for this pathogen to overcome or erode clubroot resistance is high (LeBoldus et al. 2012). The potential loss of disease management options such as resistance may be one of the more troubling aspects of clubroot – it compromises our ability to stay ahead of the pathogen. Canadian farmers rely on research and the development of new technologies to control diseases such as clubroot, but this pathogen may have evolved resources that make this an even more challenging task.

Each Prairie Province has responded differently to regulating clubroot infestations. Alberta and Saskatchewan placed clubroot on their provincial Pest Acts in 2007 and 2009, respectively, which give local municipalities powers to control the spread of this disease. Many municipalities in Alberta enacted crop rotation restrictions, limiting the number of times canola could be grown in an infested field over time. These regulations, however, are posing another challenge for canola growers, since many municipalities have enacted different rotational restrictions on infested farm fields – ranging from no restriction to 8 years of no canola cropping in fields (Murray Hartman, personal communication). Canola growers that farm in more than one municipality may face very different regulations. Saskatchewan has so far tried to take a more standardized approach at the municipal level to dealing with P. brassicae. Manitoba has not yet regulated this pest, but instead is taking the approach of communicating risk assessment and education for clubroot management.

Conclusion

Canola is a very valuable crop, with its benefits extending to consumers, to the Canadian farmers, agriculture, and to the Canadian economy. The health benefits of canola oil are well understood and accepted around the world. The recent health claim supported by the US FDA about the benefits of canola oil for heart disease risk has helped drive further demand for this product both internationally and in Canada. Canola meal too has enjoyed an increased demand for dairy rations as a result of recent studies associating it with increases in milk production (Martineau et al. 2013) and in aquaculture (Enami 2011; Luo et al. 2012; Hill et al. 2013). Farmers in the Canadian Prairie Provinces have increased production of this crop dramatically because of its profitability and relative ease of growth in this agro-climatic zone. Canola, once a minor crop, has assumed a dominant position in the Canadian agriculture industry, with the largest hectarage of any crop species in Canada in 2012 (Statistics Canada 2012a), for the first time exceeding the area sown to spring and winter wheat.

The emergence of clubroot as an infectious disease of canola in the Prairies has caused concern for the canola industry. What was originally deemed to be a minor disease has now become one of the major disease threats, even though this disease is still not widespread in the annual canola disease surveys in areas outside of the Edmonton region. As a result of the threat posed by clubroot, research on this disease has increased dramatically in Canada. The aim of this research is to achieve a better understanding of clubroot and how the canola industry may develop technologies to keep the prevalence, incidence and severity of P. brassicae at a low level in the medium and long term. Funding agencies supporting clubroot research activities have included: canola grower associations, namely the Alberta Canola Producers Commission, SaskCanola and Manitoba Canola Growers Association; provincial funding groups, such as the Alberta Crop Industry Development Fund and the Saskatchewan Agriculture Development Fund; and the Canadian federal government’s Growing Forward program, which created the Clubroot Risk Mitigation Initiative (CRMI). The CRMI in particular has been very effective at encouraging a collaborative atmosphere directed at pursuing management strategies for clubroot. A continued effort in clubroot research needs to be maintained in order to remain ahead of this disease. The success of the canola industry depends on preventing diseases like clubroot from evolving into a greater threat and reducing yields and production of this crop.