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Downey, R.K. 1990. Canola: A quality brassica oilseed. p. 211-217. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Canola: A Quality Brassica Oilseed

R.K. Downey

  9. Table 1
  10. Table 2
  11. Table 3
  12. Table 4
  13. Table 5
  14. Fig. 1
  15. Fig. 2
  16. Fig. 3


In many parts of the United States a crop called canola is being promoted. To many, both the word and the crop will be largely unknown. This is not surprising since canola is a coined name recently given to nutritionally superior seed, oil and meal produced by genetically modified rapeseed plants. Oilseed rape (Brassica napus L.) and turnip rape (B. campestris L.), although relatively recent crop introductions to the north American continent, are very new to most U.S. states. However, they have long been cultivated as oil crops in Asia and northern Europe. The seed harvested from these crops is small, round and black, brown or yellow in color. Upon crushing, the seeds yield 40 to 44% oil and a nutritionally well balanced high protein (36-37%) meal. The seed looks very much like turnip or mustard seed or seed of cabbage and broccoli, to which these crops are closely related.

The rapeseed/canola crop is the world's third most important edible oil source with an annual growth rate exceeding that of palm (Table 1). The main rapeseed-producing regions of the world are China, Canada, the Indian subcontinent, and Northern Europe, where, depending upon the duration and severity of the winter, either the annual or the biennial form of these crops is grown. In general, the biennial form of rapeseed/canola is considered to be less winter-hardy than winter barley. Throughout much of the Indian subcontinent, a third Brassica oilseed species, Brassica juncea (L.) Czern., commonly known as tame mustard, is grown on about 60% of the oilseed Brassica area.


The oilseed Brassicas are cool season crops and in Canada production is centered in the more northerly areas of the Great Plains. The Canadian development of the rapeseed/canola crop is frequently referred to as a Cinderella story. The crop has undergone a great metamorphosis in quality and production since it was first grown as an emergency war measure on a few acres in 1942. At that time, rapeseed oil was considered an essential lubricant because it could cling to water- and steam-washed metal surfaces better than any other oil. Since the naval ships and trains of the time were steam-powered, and with the European and Asian rape oil supplies cut off, Canada was asked to undertake production. The annual form of the B. napus species was introduced first, followed shortly by B. campestris.

It quickly became evident that both these crop plants were well adapted to the Canadian climate and required only minor modifications to the existing grain growing and handling system. The small round seeds necessitated seed drill adjustments to uniformly sow only a few pounds per acre. Likewise, the throat of the grain swathers had to be enlarged and a swath roller developed to reduce the risk of swaths moving in the wind. It was also found necessary to reduce the combine cylinder speed by about one-half and open the concaves wide to reduce seed cracking and expedite the handling of a large volume of material. Fortunately these adjustments were of a minor nature and did not hinder the early acceptance of these new crop species.

Under a guaranteed price support system, crop area expanded (Table 2). However, with the loss of the price support following the war and the replacement of steam power by diesel, the crop faltered until private entrepreneurs established a market in Japan where the oil was, and still is, considered a premium oil for deep fat frying.


From the outset, it was realized that oilseed rape could be a major source of edible oil for Canada, which until that time was importing almost 90% of its edible oil needs. The domestic market penetration of rapeseed oil and meal was hampered by the presence in the seed of sulfur compounds called glucosinolates. These compounds, of which about 90 are known, give the desired flavor and odor to the cole vegetables, mustard and many other cruciferous crops, but are undesirable in concentrated feeds, both for palatability and nutritional reasons. When cells of the seed are broken and moisture is present, the myrosinase enzyme hydrolyzes the glucosinolates to release sulfur, glucose and isothiocyanates (Fig. 1). The isothiocyanates are active goitergens and interfere with the iodine uptake by the thyroid gland in non-ruminant animals, such as swine and poultry. Further, some of the sulfur-containing breakdown products were often carried over into the oil, resulting in the inhibition of the catalyst required for hydrogenation in the manufacture of margarines and shortenings. To overcome these problems, the method of oilseed extraction was modified to exclude moisture from the process and to heat-inactivate the myrosinase enzyme as one of the first steps in the oil extraction process. This innovation proved to be a partial solution to the glucosinolate problem since these compounds remained intact in the meal and as such were relatively innocuous feed constituents. Based on this process, a domestic market for oil and meal began to expand. This development, together with a strong demand for seed exports, provided growers with a cash market in times of relatively high wheat surpluses.

Average yields increased over the years as growers realized that by sowing rapeseed on their best land and applying extra management and inputs, both returns and marketability were better than for cereal grains. The availability of the herbicide, Treflan, that became available about 1970-71 and which gave good control of many of the most serious weeds of rapeseed/canola, also assisted in raising average yields. Thus, by 1970, the canola crop had expanded to a total of 1.6 million hectares with an average yield of 1,259 kg/ha (1,123 lb./acre) (Table 2) and rapeseed oil had captured some 35% of the domestic edible oil market.


Canadian and European nutritionists were interested in rapeseed oil because it differed from other edible vegetable oils in its fatty acid composition. Rapeseed oil contains significant amounts of the monoenoic fatty adds with 20 (eicosenoic) and 22 (erucic) carbon chains as opposed to the common carbon chain lengths of 16 and 18 carbon atoms found in most vegetable oils (Table 3). Feeding studies with laboratory rats in the late 1940s and early 1950s suggested that these long chain fatty adds may not be the most desirable from a nutritional point of view and studies were undertaken to see if they could be reduced through plant breeding. In those days, gas chromatography was in its infancy but it did provide a relatively fast and accurate method for seed oil fatty acid analysis. The application of this technique led to the identification of low erucic acid plants in both species, with the first low erucic B. napus variety being released in 1968 and the first B. campestris variety in 1971. This change in oil composition was achieved by genetically blocking the biosynthetic pathway for fatty add carbon chain elongation as the oil is laid down in the developing seed (Fig. 2). By 1970, the nutritionists had found that the low erucic rapeseed oil was nutritionally superior to the original high erucic acid oil. As a result, Canada completely converted its 4 million acres to low erucic varieties within two years. This entirely new edible oil was found to have superior properties as a salad and cooking oil as well as being suitable for margarine and shortening blends. The shift in Canadian usage between 1971, the last year that the high erucic acid oil was used, and 1987, has been dramatic both in the proportion and amount of canola oil utilized (Fig. 3).

Further modifications in the fatty acid composition of rapeseed oil are being investigated. Of considerable interest is the development of a Brassica napus variety with a low linolenic content of less than 3%. Such an oil has been shown to have superior keeping qualities. Similarly, it is possible to raise the level of the polyunsaturated fatty acid linoleic to 30% or more and at the same time reduce the linolenic values. The breeder's dilemma at the moment is that nutritionists are saying that the present composition of the low erucic acid rapeseed oil is almost ideal, with the lowest saturated fatty acid content of any of the vegetable oils coupled with approximately 8 to 10% alpha-linolenic acid. Indeed, low erucic acid rapeseed oil was awarded the 1987 American Food Product of the Year by the American Heart Foundation of New York.


Although the development of a superior edible oil had been achieved by 1971, the continuing presence of glucosinolates in the high protein meal was a major constraint to market expansion. Even though the intact glucosinolates were only mildly anti-nutritional in non-ruminant animals, some adverse effects on feed efficiency and weight gains were found in some classes of swine and poultry when high levels of rapeseed meal was fed. Again, the development of fast, accurate chemical methods to determine the presence and amounts of the various glucosinolates led to the identification of plants of the B. napus cultivar `Bronowski' from Poland which were essentially free of the glucosinolates normally found in rapeseed. These low glucosinolate genes were incorporated into adapted high-yielding varieties of B. napus and transferred to the B. campestris species. The result has been the virtual removal of all non-economic constraints to the feeding of low glucosinolate rapeseed meal to all classes of livestock and poultry

As a result of the nutritional upgrading of the oil and the meal, a new name was required to distinguish these products from the old-style rapeseed and thus the word "canola" was coined and trademarked and defined as having less than 2% erucic acid in the oil and less than 30 micromoles of the aliphatic glucosinolates in the oil-free meal. Thus, all canola is rapeseed but not all rapeseed is canola.


As important as these new quality traits are to the market, farmers will only produce the crop if it's agronomically well-adapted and gives superior yields. Canadian breeders have not ignored this requirement, and substantial advances have been made in increasing the seed yield of B. napus while at the same time reducing the length of the growing season required (Table 4). Oil contents have also been raised significantly while protein content of the meal has been maintained. Agronomic improvements in the early maturing B. campestris cultivars that are self-incompatible cross-fertile have been more difficult to achieve, but new strains shortly to be released will have at least 7% higher seed yield and the oil content increased by about 1.5% (Table 5).

It should also be noted that as the area of canola has expanded, the problems with diseases and insects have increased substantially. Flea beetles, (Phyllotreta sp.), which attack the emerging seedlings, are a continuous threat that requires seed treatment for protection of all fields. Likewise, the lepidopterous insects can be very damaging in some locations and years. It is anticipated that the introduction of genes for specific Bacillus thuringensis toxins to control both insect genera will be possible within a few years. Diseases such as Sclerotinia, blackleg (Leptosphaeria maculans), Rhizoctonia solani and white rust (Albugo candida) are all important diseases which must be controlled either through incorporating resistance into the plant or through the use of fungicides.

In weed control, a number of herbicides are available for use in canola and cultivars tolerant to the triazine family of herbicides have been developed. Unfortunately, the triazine-tolerant material developed to date is about 20% lower yielding than the triazine-susceptible cultivars, thus limiting their use to fields that are heavily infested with cruciferous weeds such as stinkweed or wild mustard. More recently, the gene for glyphosate (Roundup) resistance has been transferred into B. napus canola plants and the progeny are now under field evaluation. There is also indication that genes for resistance to chlorsulfuron (Glean) and glufosinate ammonium (Basta) have also been transferred into canola.

In the future, hybrids are expected to raise the yield of both species of canola. Commercial hybrids of B. napus are now in their second year of official Canadian trials and it is expected that they will make their way into commercial production within the next few years.


The rapeseed/canola story has been an exciting one for Canada and it's far from over. Canola could experience a rapid growth in the United States over the next few years; however, comparative trials have yet to clearly define the area and rotations where the crop can economically compete within the presently established cropping system.


Table 1. World vegetable oil production as percent of the 10 major oil crops and percent change 1982/83 through 1987/88.

Production year
Vegetable oil 1982/83 1984/85 1986/87 1987/88 % change on
tonnage basis
Millions of tonnes
Total 10 major oils 46.1 49.8 55.2 58.0 26
Percentage of 10 major oil crops
Soybean 30.4 27.5 27.8 26.5 9
Palm 12.1 13.1 14.1 14.2 48
Rapeseed 10.8 11.6 13.1 13.2 53
Sunflower 13.0 13.0 12.8 12.9 25
Cotton 6.7 7.8 5.7 5.9 10
Groundnut 6.1 6.2 6.0 5.1 5
Source: Oil World

Table 2. Production trends in Western Canada (selected years).

Year Area (1000 ha) Yield (kg/ha)
1943 1 969
1944 4 793
1946 9 756
1948 32 1,132
1950 <1 352
1952 7 1,057
1955 55 799
1960 305 1,032
1965 574 1,107
1970 1,620 1,259
1975 1,580 1,259
1979 3,280 1,277
1980 2,100 1,510
1982 1,720 1,592
1984 2,820 1,384
1985 2,711 1,239
1986 2,642 1,440
1987 2,655 1,438
1988 3,626 1,102

Table 3. Percent fatty acid composition of Canadian vegetable oils.

Fatty acid Symbol Brassica
Canola Sunflower Soy bean
Palmitic C16:0 4.0 4.9 4.7 7.2 11.5
Stearic C18:0 1.5 1.6 1.8 4.1 3.9
Oleic C18:1 17.0 33.0 63.0 16.2 24.6
Linoleic C18:2 13.0 20.4 20.0 72.5 52.0
Linolenic C18:3 9.0 7.6 8.6 0.0 8.0
Eicosenoic C20:1 14.5 9.9 1.9 0.0 0.0
Erucic C22:1 41.0 23.0 0.0 0.0 0.0

Table 4. The relative performance of some Canadian cultivars of Brassica napus in Western Canada.

Year released Cultivar name Yield (%) Days to
% oil
in seed
% protein
in meal
1943 'Argentine' 100 101 40.5 47.1 HiEG
1954 'Golden' 101 = 41.1 43.9 HiEG
1963 'Tanka' 106 = 42.7 46.3 HiEG
1966 'Target' 109 -2 43.9 45.4 HiEG
1970 'Turret' 111 -3 44.5 45.4 HiEG
1968 'Oro' 107 +5 41.7 43.4 LowE
1973 'Midas' 118 -3 43.8 42.9 LowE
1974 'Tower' 112 -4 42.6 47.2 LowEG
1977 'Regent' 115 -3 43.1 47.0 LowEG
1981 'Andor' 119 -6 43.6 45.9 LowEG
1982 'Westar' 127 -6 44.3 46.0 LowEG
zE = erucic acid; G = glucosinolates

Table 5. Advances in agronomic performance in Brassica campestris.

% oil
in seed
% prot.
in meal
1943 'Polish' 100 40.5 43.6 HiEG
1964 'Echo' 112 40.8 43.7 HiEG
1969 'Polar' 109 42.3 44.2 HiEG
1973 'Torch' 111 40.1 43.2 LowE
1977 'Candle' 103 42.0 43.2 LowEG
1981 'Tobin' 110 42.5 43.2 LowEG
1989 'Parkland' 117 44.0 43.7 LowEG

Fig. 1. Products of myrosinase hydrolysis of the glucosinolates.

Fig. 2. Biosynthetic pathways of the major fatty acids in vegetable oilseeds.

Fig. 3. Canadian vegetable oil usage.

Last update August 27, 1997 by aw