Canola varieties grown in Canada belong to the Brassica napus, B. rapa or B. juncea species, which in turn belong to the much larger mustard family. Since B. napus and B. rapa species were first introduced in Canada, plant breeders have developed many varieties. The development of these varieties with major improvements in agronomic, oil and meal quality greatly influenced the rapid expansion of the canola industry in Canada, especially during the last decade. Improved seed quality increased the market for canola seed and its products. In 2002, B. juncea was introduced under contract production. There are considerable differences in agronomic characteristics and yield between species and between varieties. Evaluate these differences carefully when selecting a variety to grow. Choose the variety that is best suited to local conditions.
Brassica Species and Relatives
Canola is comprised of three species that are modified forms (using traditional plant breeding methods) of rapeseed or brown mustard:
- Brassica rapa or Polish canola
- Brassica napus or Argentine canola
- Brassica juncea - canola quality brown mustard
Until the early 1990's, Brassica rapa was referred to as Brassica campestris. The difference in species name arose from an error in classification made by the 18th Century father of taxonomy, Carolus Linnaeus. He named the turnip producing Brassica species B. rapa-rapa being Latin for root.
Linnaeus later discovered a related plant that he believed was different from B. rapa. He gave this vegetable oilproducing plant the name B. campestris. A review of his classification by taxonomists in the late 20th Century found that the two plants in fact belonged to the same species and were cross fertile. Since Brassica rapa was the name first associated with the species, the decision was made to eliminate the use of the term Brassica campestris in favour of Brassica rapa.
B. rapa, B. napus and B. juncea species belong to the Cruciferae (mustard) family. The mustard family consists of about 3,000 species of plants found mainly in the northern hemisphere. The name crucifer originates from the arrangement of the plants flower petals-diagonally opposite each other in the form of a cross. Many Brassica species have been cultivated since prehistoric times for their edible roots, stems, leaves, buds, flowers and seeds. Members of the B. rapa species include turnip, Chinese cabbage and canola. Members of the B. napus species include rutabaga and canola. B. juncea species include mustard greens, various leaf mustards and brown or Indian mustard.
Rapeseed is closely related to other Brassica species like cabbage, cauliflower, kale, and brown and oriental mustard. The relationships are important to canola plant breeders since they provide wide sources of genetic features for research purposes. Figure 1 outlines the close relationships between Brassica species. B. napus, with its 19 chromosomes, originated about 1,000 years ago from a cross between B. oleracea (cabbage=nine chromosomes) and B. rapa (turnip=10 chromosomes). The same is true for B. juncea, which originated from a cross between B. nigra (black mustard) and B. rapa (turnip).
Figure 1. Brassica Crop Relationships
More distantly related to rapeseed are the species Sinapis alba (white mustard) and Sinapis arvesis (wild mustard). These two species were formerly referred to as Brassica hirta and Brassica kaber, respectively. Besides wild mustard, the Cruciferae family also contains a host of weed species including:
- stinkweed-Thlapsi arvense L.
- wild radish-Raphanus raphanistrum L.
- shepherd's purse-Capsella bursa-pastoris (L.) Medic.
- dog mustard-Erucastrum gallicum (Willd.) Schulz
- flixweed-Descurainia sophia (L.) Webb.
- common peppergrass-Lepidium densiflorum Schrad.
- ball mustard-Neslia paniculata (L.) Desv.
History of Canola in Canada
History suggests that rapeseed was cultivated as early as the 20th century B.C. in India, and was introduced into China and Japan about the time of Christ. References to its use or that of a close relative appear in the earliest writings of European and Asian civilizations. Rapeseed plants have the ability to grow at relatively low temperatures with far less heat units required than other oilseed crops. Therefore, rapeseed was one of the very few oil sources that could be successfully grown in temperate extremes. This led to rapeseed being grown in Europe as early as the 13th century. In later centuries, rapeseed was used for both cooking and lighting, as its oil produced a smokeless white flame. Rapeseed had a rather limited industrial acceptance until the development of steam power, when it was discovered that rapeseed oil would cling to water and steam washed metal surfaces better than any other lubricant. It was this special property that led to the introduction of rapeseed into Canada.
The need for Canadian rapeseed production arose from the critical shortage of rapeseed oil that followed the World War II blockade of European and Asian sources in the early 1940's. The oil was urgently needed as a lubricant for the rapidly increasing number of marine engines in naval and merchant ships.
Argentine Type (B. napus)
Prior to World War II, rapeseed had been grown in Canada but only in small research trials at experimental farms and research stations. The trials showed that rapeseed could be successfully grown in both eastern and western Canada. Because of the need for rapeseed oil production in the spring of 1942, a small amount of seed from research trials was distributed to a few experimental farms and stations. However, only 1,200 kg (2,645 lb) was harvested that fall. A considerably larger quantity of seed than this was required for planting in 1943 to relieve the serious shortage of rapeseed oil. This led to the location and purchase of 19,000 kg (41,000 lb) of rapeseed from U.S. seed companies. This B. napus seed had originally been secured from Argentina. Therefore the name "Argentine" rapeseed was widely used in the early years of production and is still used in Canada as an unofficial name for B. napus varieties. This seed was sown on 1,300 ha (3,200 ac) in 1943 with a harvest of 1 million kg (2.2 million lb). Growers received a good return for their production which stimulated an expansion of B. napus acreage the following year.
Polish Type (B. rapa)
A Shellbrook, SK farmer in 1936 obtained some rapeseed from a friend or relative in Poland. He grew this seed in his garden for a few years and found the plants well adapted. However, at this time, there were no established markets in Canada for rapeseed. With the coming of the war, and the release of information about the need for rapeseed production, the Shellbrook farmer increased his seed supply and sold seed to his neighbors. Due to the Polish origin of both the farmer and the seed, the species he grew became known in Canada as "Polish" rapeseed. It was later established that this rapeseed belonged to the B. rapa species. Since seed of the B. rapa species was widely distributed at the outset of production, it dominated the acreage for a few years. Yield tests showed that B. napus out yielded B. rapa. However, the earlier maturity and greater shatter resistance of B. rapa made it better adapted to short season growing areas. It soon occupied more acres than B. napus.
Canola Quality B. juncea
Canola oil quality B. juncea was developed through traditional breeding methods by Agriculture and Agri- Food Canada (AAFC) Saskatoon, SK Research Centre and Saskatchewan Wheat Pool (SWP). B. juncea is the same species used to produce oriental and brown mustard varieties. In 2002, SWP introduced the first two varieties, Arid and Amulet, under contract production. This species is more suitable to the hotter, drier regions of the southern prairies and will be most adapted to the brown soil zone. B. juncea pods do not shatter as easily as other canola varieties therefore producers will be able to straight combine the crop.
Variety development is a team effort that involves plant breeders, pathologists, crop quality chemists, physiologists and agronomists - as well as highly trained technicians to back up these professionals. The plant breeders make crosses among promising materials and select for yield and quality characteristics. After several years of selection, promising lines are entered into private and public evaluation trials called Co-operative Tests that are located at over 20 locations across western Canada. After one year of testing in private trials plus one to two years in the public Co-operative Tests, the lines that meet all the required standards for oil quality, yield, herbicide tolerance and disease resistance are evaluated by the Western Canada Canola/Rapeseed Recommending Committee. Lines that meet the criteria of the Committee are recommended to the Canadian Food Inspection Agency for registration.
It usually requires eight to 10 years from the initial crosses until a variety is registered, followed by an additional two to three years of seed multiplication before a variety is available for commercial production. Rapeseed breeding began soon after the crop was introduced at AAFC, Saskatoon. Other rapeseed breeding programs were initiated at the University of Manitoba in Winnipeg, MB in 1953 and at the University of Alberta, in Edmonton, AB in 1969 to develop more regionally adapted varieties. Breeding programs were later established at the University of Guelph, in Guelph, ON and the AAFC Beaverlodge, AB Research Centre.
The original seed stocks of the B. napus species from Argentina contained a mixture of plant types, and were not licensed. However, these seed stocks provided the genetic material for the development of Canadian B. napus varieties. Similarly, the B. rapa seed stocks originally from Poland were not licensed, but were utilized in breeding programs for the development of later varieties.
Early breeding programs concentrated on improvements in agronomic characteristics and in oil content. The first rapeseed variety licensed in Canada was released from AAFC Saskatoon. Here's a list of rapeseed varieties and when they were introduced:
- Golden (1954) - a B. napus selection from Argentina with improved oil content and lodging resistance (AAFC, Saskatoon)
- Arlo (1958) - a B. rapa Swedish variety
- Nugget (1961) - a B. napus selection from Argentina with improved oil
- Tanka (1963) - a B. napus selection from Golden with improved yield and seed size (University of Manitoba)
- Echo (1964) - a B. rapa selection from Polish with improved yield (AAFC, Indian Head, SK)
- Target (1966) - a B. napus selection from Tanka with a major improvement in maturity, plant height, oil content and yield (University of Manitoba)
- Polar (1969) - a B. rapa selection from Polish with improved oil and protein content (University of Manitoba)
- Turret (1970) - a B. napus selection from Target with improved maturity, oil contents and yield (University of Manitoba)
Fatty Acid Profiles in Edible Oils
Edible vegetable oils are made up of fatty acids. The types of fatty acids determine whether a vegetable oil is used for edible or industrial purposes. Certain fatty acids such as linoleic are considered essential in human diets since they cannot be synthesized by the body but must be obtained from the diet. All of the rapeseed varieties presented above produced oils containing large amounts of eicosenoic and erucic acids which are not considered essential for human growth. A comparison of rapeseed oil to other vegetable oils is shown in Table 1.
Table 1. Comparative Analysis of Fatty Acid Contents of Vegetable Oils
|Vegetable Oil||Major Fatty Acids (%)|
|High erucic rapeseed
Low Erucic Acid Rapeseed Varieties
As early as 1956, the nutritional aspects of rapeseed oil were questioned, especially the high eicosenoic and erucic fatty acid contents. Canadian plant breeders responded quickly with isolation of rapeseed plants with low eicosenoic and erucic acid content-by 1960 for B. napus and 1964 for B. rapa. These desirable characteristics were then bred into suitable varieties. Here's a list of low erucic varieties introduced:
- Oro (1968) - the first low erucic acid B. napus selection from crosses between Nugget and an unlicensed forage crop cultivar Liho, which contained low erucic acid (AAFC, Saskatoon)
- Zephyr (1971) - a B. napus selection from an Oro X Target cross with improved oil and protein content (AAFC, Saskatoon)
- Span (1971) - the first low erucic acid B. rapa variety developed from low erucic acid selections from Polish and Arlo (AAFC, Saskatoon)
- Torch (1973) - a B. rapa selection from Span with improved yield (AAFC, Saskatoon)
- Midas (1973) - a B. napus selection from crosses between Target and a low erucic acid source with yields equal to Target but lower in protein content (AAFC, Saskatoon)
The development of low erucic varieties represented a major quality improvement and allowed Canada to first establish a maximum level of 5% erucic acid in the oil component of the seed. Continual improvements in canola varieties through plant breeding have allowed this maximum to be reduced to less than 2% erucic acid, which is currently the world standard.
Low Erucic Acid and Low Glucosinolate Canola Varieties
While the rapeseed oil quality changes were being bred into suitable varieties, plant breeders were also working hard with animal nutritionists to change the meal quality. Rapeseed meal is an excellent source of protein with a favourable balance of amino acids. However, the use of rapeseed meal in rations was limited by its glucosinolate content. Most plants of the mustard family contain glucosinolates. Glucosinolates are responsible for the pungent odour and biting taste, which ranges from the hot flavour in mustard seed and horseradish, to the more subtle flavours of rutabaga and cauliflower.
The glucosinolates in rapeseed led to palatability and nutritional problems when fed to livestock and poultry. The glucosinolates break down into other compounds during crushing and feed formulation. High levels of glucosinolates in rations fed to livestock and poultry resulted in reduced feed efficacy. For this reason, plant breeders searched for genetic material low in glucosinolates. In 1967, seeds from plants of the Polish variety Bronowski were found to be low in glucosinolates. This genetic source for low glucosinolates content was then utilized to develop low erucic, low glucosinolate varieties.
The University of Manitoba developed the first low erucic acid, low glucosinolate variety, Tower, in 1974. The term "double low" is used to describe varieties with low erucic acid and low glucosinolate levels. In 1977, two more "double low" varieties were registered, the first Polish variety, Candle, developed by AAFC, Saskatoon, and the second Argentine variety, Regent, developed by the University of Manitoba. Canada became the first country in the world to produce large quantities of rapeseed with low erucic acid in the oil and low glucosinolates in the meal.
This new improved quality in the seed, oil and meal needed a name to distinguish the commodity from common rapeseed. The term "canola" derived from "Canadian oil" was adopted. The term "canola" is not just a Canadian term and is no longer an industry trademark. Canola is defined in Canadian food acts, feed acts and the Seeds Act. The official definition of canola is: "An oil that must contain less than 2% erucic acid, and less than 30 micromoles of glucosinolates per gram of air-dried oil-free meal." Except for specialty fatty acid varieties like high erucic acid destined for specialty industrial markets, the varieties registered in Canada must be of canola quality.
Canola oil quality B. juncea was developed by AAFC, Saskatoon and Saskatchewan Wheat Pool by changing the fatty acid profile to that found in B. napus and B. rapa and reducing the erucic acid and glucosinolates levels to the canola standard.
Conventional canola is tolerant to a variety of herbicides. Through mutagenesis and gene transfer, plant breeders have developed canola that is tolerant to specific herbicides or groups of herbicides. Here is a list:
- Triazine-tolerant canola (TTC) was developed to allow growers to plant canola on fields infested with cruciferous weeds such as wild mustard, stinkweed, ball mustard and a number of other weedsmany of which cannot be controlled by herbicides in conventional canola. Unfortunately the triazine resistance from the B. rapa weed (bird's rape) is due to a cytoplasmic mutant, which meant that TTC varieties yielded considerably less when compared to conventional canola varieties under weed-free conditions. Early work on triazine-tolerant canola took place at the University of Guelph, with the first B. napus variety, OAC Triton, registered in 1984.
- In 1995, the first imidazolinone-tolerant (Pursuit + Odyssey herbicides) B. napus variety "45A71" was registered. This variety and others contain a tolerance trait that was developed through mutagenesis by Cyanamid (now BASF).
- In 1995, the first transgenic B. napus variety, Quest, was registered. Quest is tolerant to the herbicide glyphosate (Roundup) and was developed by Monsanto.
- Innovator and Independence were granted registration in 1995. These transgenic B. napus varieties were developed by Aventis and contain a gene that provided resistance to the herbicide glufosinate ammonium (Liberty).
- In 1999, several bromoxynil-resistant varieties-295 BX, Armor BX, and Zodiac BX-were developed by the University of Manitoba.
From 1995 to 2001, over 100 herbicide-tolerant varieties were recommended for registration.
Hybrids and Synthetics
A canola hybrid is simply the result of crossbreeding two lines of canola. Research in the greenhouse showed that making hand crosses between two distantly related lines of canola resulted in yields that were up to 45% higher than either parent line. This increased yield is the result of heterosis or hybrid vigour. The more distantly related the parents, the greater the resulting hybrid vigour. However, producing hybrid seed by hand for large volumes of seed is economically impractical. Since B. napus varieties are mainly self-pollinated, the self-pollination of the parent lines must be controlled to make hybridization commercially feasible.
To date, several approaches have been taken to develop hybridization systems in B. napus. The first relatively successful programs utilized more traditional hybrid breeding methods such as cytoplasmic male sterility (CMS). Researchers discovered that some Brassica species and close relatives had male-sterile cytoplasm (material surrounding the nucleus of a cell). At the cellular level, fertility is controlled by an interaction between the cell nucleus and cytoplasm. The CMS systems for canola hybridization depend upon this mutation in certain cytoplasmic bodies that result in failure to develop functional pollen or anthers. Use of CMS allowed canola breeders to produce canola female plants that either fail to make pollen, fail to shed pollen or make pollen that is unable to cause selffertilization. The hybrid system is normally composed of three components-a male-sterile Line A, a maintainer Line B and a restorer Line R (Figure 2).
Figure 2. Hybrid Seed Production
Female plant flowers from Line A have a sterile cytoplasm and do not produce pollen and cannot self-pollinate. This CMS characteristic is inherited maternally, therefore, when a CMS female Line A, is crossed with a genetically identical maintainer Line B that produces pollen, all the seed produced retains the CMS trait. The restorer Line R is genetically different from Line A and contains nuclear genes that compensate for the defect in the cytoplasm and restore fertility to the hybrid cross. The first commercial CMS B. napus hybrid, Hyola 40, was registered in 1989 by Advanta Seeds. This was quickly followed by the very popular hybrid Hyola 401 in 1991.
A novel hybridization system was developed by Plant Genetic Systems in Belgium through biotechnology. This system involves the use of two parental lines. The first parental line is male sterile, does not produce viable pollen grains and cannot self-pollinate. A gene isolated from a common soil bacterium and inserted into the parental line causes this nuclear male sterility. The gene controls production of a specific enzyme in a specific anther cell layer and at a specific stage of anther development resulting in no pollen production. The second parental line contains another gene, obtained from the same common soil bacterium that produces an inhibitor enzyme that counteracts the sterility enzyme in the first parental line to restore fertility. A gene that confers tolerance to the herbicide glufosinate ammonium (Liberty) was inserted into both parental lines. When the two lines are crossed, the progeny is a 100% true hybrid. And since fertility is restored, the hybrid plants are fully fertile and produce seed. The first Liberty-tolerant hybrids-"3850 and 3880"-were registered in 1996 by Aventis (now Bayer CropScience).
Hybrid breeding techniques, while reasonably successful in B. napus, have not been successful in B. rapa variety development. An alternative breeding method to exploit the heterosis available in the Brassica family is the production of "synthetic" varieties. Synthetic canola varieties are developed by blending seed from one parent with seed from another parent and growing out the mixed seed to produce a Certified synthetic seed (Figure 3).
Figure 3. Synthetic B. rapa Canola Breeding and Multiplication
Synthetics of B. rapa are usually composed of two, or at most three, parental lines. The resulting Certified synthetic seed composed of a mixture of hybrid and parental plants tends to be more stable over a wider range of environmental conditions than conventional varieties. In comparison, a synthetic canola variety is usually intermediate between conventional varieties and hybrids in terms of capturing heterosis. B. rapa canola is selfincompatible, meaning the plant cannot self-pollinate with pollen from a flower on the same plant, but must pollinate with other plants in the field. This self-incompatibility in B. rapa is an advantage in making synthetic varieties. The first B. rapa synthetic varieties, Hysyn 100 and Hysyn 110, were registered in 1994 by Advanta Seeds.
Synthetics of B. napus are developed from two or more parental lines, which are then mixed in equal proportions (although not always) and grown in isolation. As B. napus is self-compatible and the degree of outcrossing is dependent on insect pollination, there will be varying degrees of crossing between the parental lines. The seed of the next generation will be a mixture of the parental lines and all possible hybrids between them. For example, a three parent synthetic would include the original three parental lines and the three possible hybrids. This process can be continued for another generation before the seed is released as certified. As the degree of outcrossing is variable, it is difficult to predict what levels of heterosis will be achieved in the commercial seed. The first synthetic B. napus variety registered in Canada was Synbrid 220 in 1997.
Winter Canola Varieties
Winter (fall-seeded) rapeseed is widely grown in parts of Europe and Asia. The term rapeseed is used, but many of the varieties have similar erucic acid and glucosinolate levels to Canadian varieties and fit the canola definition. Winter rapeseed greatly out yields spring types as shown by Swedish yield data in Table 2.
Table 2. Average Yield in Sweden of Four Types of Rapeseed
|Rapeseed Type||Average Yields 1976-79|
|Winter rapeseed (B. napus)
|Winter turnip rapeseed (B. rapa)
|Spring rapeseed (B. napus)
|Spring turnip rapeseed (B. rapa)
Early winter varieties introduced and registered in Canada were of European origin. Since they did not meet the standards for glucosinolates, they were rapeseed varieties. However, later breeding work in Europe and eastern Canada produced winter canola varieties. The first Canadian-bred winter canola, OAC Winfield, was developed by the University of Guelph, in Guelph, ON and registered in 1988. In western Canada, winter canola is not grown commercially because of unsatisfactory winter hardiness. An occasional crop of a hardy variety may survive some winters in the southern prairies, but attempts to grow it consistently have always failed. Winter canola is slightly less winter hardy than winter barley that also rarely survives prairie winters. A major increase in winter hardiness is required for successful production in western Canada. Varieties with this degree of winter hardiness have not been observed to date anywhere in the world.
Research trials by the University of Guelph have shown that winter canola has limited potential for some areas of Ontario. Where winter canola over-winters, it will out yield spring canola by 40 to 50%. Management studies at many locations throughout Ontario have shown that winter canola has the best chance of winter survival and high yields when grown on well-drained, lighter-textured loam soils and on sandy loam soils in southern Ontario with good snow cover. Winter survival is not very good on heavy clay soils or soils with poor drainage due to heaving.
Specialty Fatty Acid Varieties
Canola oil is accepted around the world as a healthy oil low in saturated fat. However, there are markets available for oils with specific oil characteristics for special functions. Specialty fatty acid canola varieties are tested and recommended for registration by the Specialty and Contract Registration Committee, a sub-committee of the Western Canada Canola/Rapeseed Recommending Committee. Specialty varieties are restricted to contract production through private companies.
High Erucic Acid Rapeseed
Prior to the reduction in erucic acid levels which produced canola, rapeseed oil was used both for edible and industrial purposes. The high levels of erucic acid made the oil useful in the production of lubricants. Today there remains a market for a significant acreage of high erucic acid rapeseed oil for use in plastics, lubricants, lacquers and detergents.
Plant breeders increased the erucic acid level in conventional rapeseed to produce High Erucic Acid Rapeseed (HEAR). At the same time, they reduced the glucosinolate levels so that the meal from HEAR varieties was more readily marketable as a livestock feed. The first HEAR (B. rapa) variety, R-500, was developed at the Agriculture and Agri-Food Canada Saskatoon, SK Research Centre. It produced a high-glucosinolate meal. The second HEAR (B. napus) variety, Reston, was registered in 1982 by the University of Manitoba, in Winnipeg, MB. It contained 40 to 48% erucic acid and medium glucosinolate levels. It was de-registered in 1989. Since then many "HEAR" varieties have been developed and released by the University of Manitoba.
Low Linolenic and Low Linolenic/High Oleic Canola
Plant breeders also recognized that by manipulating other fatty acids different nutrient and processing characteristics could be produced in the resulting oil. The first variety in this category was developed at the University of Manitoba and registered in 1987 under the name Stellar. Stellar had a reduced linolenic fatty acid content (3%), which resulted in significant improvements in the processing and keeping quality of the oil. High linolenic acid makes oil go rancid. Since Stellar, companies such as Cargill Specialty Canola Oils, Pioneer Hi-Bred and Dow AgroSciences have registered varieties with modified fatty acid profiles, such as high oleic, low linolenic or high oleic and low linolenic.
Future Variety Developments
For the past decade varieties have changed rapidly as new quality and agronomic characteristics have been introduced. If Canadian canola plant breeders are as successful as they have been in the past, there will be many breeding improvements to look forward to in the next decade. Potential breeding improvements that plant breeders are working toward include:
- resistance to drought stress
- frost tolerance (late spring and early fall frosts)
- elimination of green seed
- nutrient use efficiency
- low saturated fatty acid content
- early maturing Argentine varieties for shorter frostfree areas
- new herbicide tolerance
- disease resistance - seedling blight, brown girdling root rot, etc.
- insect resistance - root maggot, cabbage seedpod weevil, etc.
- cold temperature tolerance for improved germination and emergence
- larger seed size
- improved winter hardiness and yield in winter canola
- higher yielding hybrids
There has been a rapid proliferation of registered conventional, herbicide-tolerant and specialty fatty acid canola varieties. In the past decade, over 200 varieties have been registered and over 50 de-registered. This increases the complexity in deciding which variety to grow. Some of the factors to consider when choosing a variety are shown in Figure 4.
Figure 4. Factors to Consider in Choosing a Variety
Seed yields and agronomic characteristics vary not only between species but also between varieties. Because of this, and the fact that the number of varieties now available is so large, before deciding on which varieties to seed, review as much information as possible.
Pay particular attention to information from provincial variety testing trials and Canola Council of Canada Canola Production Centre trials. Regional variety testing programs, conducted extensively throughout each of the provinces, provide the agronomic performance of registered or recommended varieties, under the different environmental production areas. When planting an unfamiliar variety, consider planting only a portion of the acreage to that variety. This will allow time to assess how the variety performs on the farm before committing a large acreage.
In provincial canola variety trials, yields can differ from 25 to 35% between high and low yielding B. napus varieties. Under good moisture and frost-free conditions, B. napus varieties yield 15 to 20% higher than B. rapa varieties. However, where summer droughts and early spring or fall frosts occur, yields can be similar.
All registered varieties have the genetics for reasonably high yield, but many more production factors can have a greater impact on yield than the variety itself. While yield is an important factor in variety selection, do not use it as the only selection criteria. Look for stable, consistent performance over years and locations when evaluating varieties. Most varieties go through a multitude of testing and the data generated can be useful in making decisions. Growers may not want a variety that averaged 115% above the checks for a specific area if they know that its performance ranged from 60 to 170% of the checks over years and locations. The yields reported from variety trials are not precise and as a rule of thumb the precision is a plus or minus 8 to 10%. For example, in evaluating two varieties -one that is 109% of the check compared to another at 101% of the check-expect no yield difference between the two in a field.
Look to these sources for variety selection data:
- Western Canada Canola/Rapeseed Recommending Committee Co-operative Trials
- provincial canola regional trials
- crop insurance farmer reported yields-Alberta Management Insights, Manitoba Management Plus Program, Saskatchewan Management Plus Program
- Canola Council of Canada variety trials
- private seed company trials and demonstrations
- local trials-municipal, agricultural service boards, etc.
Information on variety performance can be obtained either from government or company Web sites or publications, including:
A partial budget is a useful tool when comparing varieties to evaluate not only the cost of the variety but also the differences in herbicide costs and/or technical use agreements.
Growers should make certain the varieties they select meet the requirements of their farming practices, timing of farming operations, frost-free periods at their location, and growing climate.
Days to Maturity
Relative maturity ratings are the average number of days from seeding to swathing. The actual number of days to reach maturity depends on local climate and to some extent on management practices.
The accumulation of temperature or Growing Degree Days (GDDs) has a major influence on days to maturity for canola. In the short and mid-season zones of western Canada, maturity for B. napus varieties will range from 95 to 125 days depending on the growing season heat accumulation (Figure 5). Within any particular year, the maturity difference between early and late maturing varieties will range from five to nine days. B. rapa varieties are usually 10 days to four weeks earlier and range from 80 to 115 days to maturity. The difference between B. rapa varieties on a yearly basis is usually three to five days.
Figure 5. Relative Ranges for Crops-Short and Mid-Season Zones
Risk of Frost
Consider the risks of spring and fall frost damage. Spring frosts can reduce plant stands or set the crop back. Fall frosts can result in green seed. Whether a crop matures before the first killing frost depends on seeding date, heat accumulation and management practices. In shorter frostfree areas, an early maturing B. napus variety sown early may be a better choice than a B. rapa variety sown later in May. However, if the B. napus variety cannot be sown early the better choice may a B. rapa variety sown when field conditions and weather allow. B. napus varieties are slightly more susceptible to late spring frosts than cereals, and are susceptible to early fall frosts. B. rapa varieties are less susceptible to late spring frosts and usually mature before fall frosts. Obtain long-term records of GDDs and spring and fall frost probabilities for the location to assist in variety choice.
Potential for Drought
Both species of canola have poor drought tolerance for germination and emergence during plant establishment. After establishment both species have drought tolerance similar to cereals. However, B. napus varieties may suffer loss in yield and quality from late summer drought while B. rapa varieties often mature early enough to escape late summer drought. B. juncea is considered to be more drought tolerant than B. napus and B. rapa.
While lodging varies with the variety, agro-climatic conditions also influence the plants height and lodging resistance. Depending on growing conditions, B. napus varieties range from 75 to 175 cm (30 to 69") while B. rapa varieties range from 50 to 125 cm (20 to 49"). In field tests, the two B. juncea varieties were comparable to B. napus. B. juncea grows more upright than B. napus canola and has less tendency to lodge. In irrigated or high rainfall and cooler growing areas, canola tends to grow taller and have an increased risk of lodging. Under these conditions, straw strength or lodging resistance and fertility are important factors to consider. Fall and early seeded canola crops are shorter than mid-May sown crops.
High Temperatures During Flowering
B. napus varieties may flower during high temperature periods in July with reduced pod and seed set. Fall or early seeding may allow the B. napus varieties to flower earlier and escape high temperature damage. B. rapa varieties sown in mid May usually finish flowering before high temperatures occur.
The benefits of a good rotation will probably have more impact than variety selection over the long term for such factors as disease, weeds, insects and soil fertility. Variety selection is not a good substitute for crop rotation. The crop type and variety seeded in the past will affect future choices. Canola is an excellent rotation break for cereals. Canola residue provides a biofumigant for control of some cereal root diseases. A good crop rotation can assist in controlling problems with volunteers, diseases, herbicide residues and weeds. For example, sowing a Clearfield (imidazolinonetolerant) variety following field peas that were sprayed with Pursuit will reduce potential risk of crop damage from herbicide residues. Canola yields tend to be higher in rotations following cereals or summerfallow (Figure 6).
Figure 6. Canola Yield in Black - Dark Grey Soil Zone on Various Crop Stubbles
Risk of Diseases, Insects and Weeds
Blackleg disease resistance is an important consideration in areas where the disease is widespread. Varieties with superior lodging resistance reduce the incidence of sclerotinia. Tall varieties tend to be more susceptible to sclerotinia stem rot, especially if lodging occurs. Apetalous varieties are also less susceptible to sclerotinia stem rot. B. napus varieties are generally more resistant to diseases like brown girdling root rot than B. rapa varieties. With high infestations of cabbage root maggot, B. napus yield losses are much less than with B. rapa varieties. Herbicide-tolerant canola varieties may provide another strategy for controlling difficult or herbicide-resistant weeds.
B. rapa and B. juncea varieties are more resistant to shattering and may be straight combined. B. napus varieties shatter readily when ripe and should be swathed. Harvestability-a combination of height, lodging resistance, podding depth and plant density-is a measure of the ease with which a canola variety can be swathed and combined. If plant height and ease of swathing have been a problem in the past, consider shorter varieties with good lodging resistance. See the Canola Council of Canada's Canola Production Centre Annual Report for harvestability ratings of current varieties.
Plant Breeders' Rights
On August 1, 1990 Plant Breeders' Rights (PBR) legislation was enacted in Canada. PBR provide a way to assure that companies and institutions that invest in plant breeding are able to keep reasonable control of their varieties and secure fair compensation for their efforts. This encourages additional investment in improved crop varieties for Canadian farmers.
PBR for crop variety developers are comparable in many ways to patent protection in other areas. When plant breeders develop a new variety for use in Canada, they may apply under the Plant Breeders' Rights Act to obtain certain controls over the multiplication and sale of the seed of that variety. Sale, trade or any other transfer of the seed for propagation purposes is prohibited by law without:
- written permission of the breeder or the breeder's agent
- payment of a royalty to the breeder or the breeder's agent
Under PBR, farmers are allowed to save seed of the variety for their own use, on their own farms.
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