Rapeseed is a major crop in India (Mustard), grown on 13% of cropped land. Rapeseed oil is an Edible Oil in India. Exports of all Edible Oils (including Rapeseed Oil) from India are banned. It is the most favored vegetable oil, in Europe for the manufacture of Biodiesel and is in great demand there. Rapeseed was the third leading source of vegetable oil in the world in 2000, after soy and palm. Rapeseed is the world's second leading source of protein meal. (It is only one-fifth of the production of the soy meal.) In Europe, rapeseed is primarily cultivated for animal feed (due to its very high lipidic and medium proteinic content), and for the production of vegetable oil for biodiesel.
Natural rapeseed oil contains erucic acid, which is mildly toxic to humans in large doses but is used as a food additive in smaller doses. Canola is a specific variety of rapeseed bred to have a low erucic acid content. Canola was developed in Canada and its name is a combination of "Canada" and "Oil" (Canadian oil low acid, more precisely). The name was also chosen partly for obvious marketing reasons. The rapeseed is the valuable, harvested component of the crop. The crop is also grown as a winter-cover crop. It provides good coverage of the soil in winter, and limits nitrogen run-off. The plant is ploughed back in the soil or used as bedding. Processing of rape seed for oil production provides a rapeseed animal meal as a by-product. The by-product is a high-protein animal feed.
Rapeseed has been linked with adverse effects in asthma and hay fever sufferers. Some suggest that oilseed pollen is the cause of increased breathing difficulties. This is unlikely however, as rapeseed is an entomophilous crop, with pollen transfer primarily by insects. Others suggest that it is the inhalation of oilseed rape dust that causes this, and that allergies to the pollen are relatively rare. There may also be a another effect at work - since rapeseed in flower has a distinctive and pungent smell, hay fever sufferers may wrongly jump to the conclusion that it's the rapeseed that's to blame simply because they can smell it. There is also some recent evidence that the extensive use of this and similar vegetable oils in food is leading to a significant increase in cases of macular degeneration of the eye. Some varieties of rapeseed are sold as greens in asian groceries. Rapeseed (or canola) is a heavy nectar producer, and honeybees produce a light colored, but peppery honey from it. It must be extracted immediately after processing is finished, as it will quickly granulate in the honeycomb and will be impossible to extract. The honey is usually blended with milder honeys, if used for table use, or sold as bakery grade. Seed producers contract with beekeepers for the pollination of the seed.

Rapeseed (also known as Rape, Oilseed Rape, Rapa, Rapaseed and for some cultivars Canola) known scientifically as Brassica napus, is a bright yellow flowering member of the brassicaceae (also known as the mustard family). The name is derived through Old English from a term for turnip, rapum. Some botanists include the closely related Brassica campestris within B. napus. Rapeseed is the third most important source of vegetable oil in the world, after soybean and palm oil. During the past twenty years, it has passed peanut, cottonseed, and most recently, sunflower, in worldwide production. This is almost entirely due to the plant breeding work which greatly reduced the levels of two anti-nutritional compounds, erucic acid in the oil and glucosinolates in the meal, creating a new, high-value oil and protein crop.
Double low rapeseed, as defined by European Community standards, has less than 35 µmol of total glucosinolates tel quel. The term "industrial rapeseed" does not have any regulatory basis but refers to any rapeseed with a high content of erucic acid in the oil. For most purposes, the limit is 45%, although higher contents are considered desirable. The term "single low" refers to high glucosinolate rapeseed with low erucic oil. High erucic cultivars with low glucosinolate content also exist.

Botanical Features

Rapeseed is derived from two Brassica species, B. napus L. and B. rapa L. To distinguish between them B. rapa is often called turnip rape and B. napus is called Swede rape. Spring and winter types exist of both species. The rapeseed oil of world commerce comes from these two species and to a minor extent also from the mustards, especially B. juncea Coss. (brown mustard) and Sinapis alba. L. (yellow mustard).

Taxonomy

In addition to B. napus L. and B. rapa L., Brassica includes cultivated species B. carinata Braun (Abyssinian mustard), B. nigra Koch, and B. oleracea L. The four most widely cultivated species, B. juncea, B. napus, B. oleracea, and B. rapa are highly polymorphic including oilseed crops, root crops, and vegetables such as Chinese cabbage, broccoli, and Brussel sprouts.
The relationships among the cultivated species were largely clarified by cytological work of Morinaga (1934). According to his hypothesis, the high chromosome number of species B. napus (2n = 38, AACC), B. juncea (2n = 36, AABB), and B. carinata (2n = 34, BBCC) are amphidiploids combining in pairs the chromosome sets of the low chromosome number species B. nigra (2n = 16, BB), B. oleracea (2n = 18, CC), and B. rapa (2n = 20, AA). This hypothesis was verified by U (1935) with successful re-synthesis of B. napus. Re-synthesis of B. juncea and B. carinata was accomplished later by Frandsen (1943, 1947). The low chromosome number species may have developed from ancestral species with even lower chromosome numbers as suggested by Robbelen (1960).

Origin

Brassica crops may be among the oldest cultivated plants known to man. In India, B. rapa is mentioned in ancient Sanskrut literature from ca. 1500 BC and seed of B. juncea have been found in archaeological sites dating back to ca. 2300 BC (Prakash 1980). Rapeseed production has a long history in China. The Chinese word for rapeseed was first recorded ca. 2500 years ago, and the oldest archaeological discoveries may date back as far as to ca. 5000 BC (Yan 1990).
Historically, B. rapa seems to have the widest distribution of Brassica oilseeds. At least 2000 years ago, it was distributed from northern Europe to China and Korea, with primary center of diversity in the Himalayan region (Hedge 1976).
Brassica napus has probably developed in the area where the wild forms of its ancestral species are sympatric, in the Mediterranean area. Wild forms of B. napus are unknown, so it is possible it originated in cultivation. Production of oilseed B. napus probably started in Europe during the middle-ages; B. napus was introduced to Asia during the 19th century. The present Chinese and Japanese germplasm was developed crossing European B. napus with different indigenous B. rapa cultivars (Shiga 1970).

Distribution

World rapeseed production exceeds 20 million hectares, making it the third most important oil plant in the world after palm oil and soybean. The leading producers in 1991 were China, India, European Community, and Canada with estimated areas of 6.13, 6.10, 2.43, and 3.14 million hectares, respectively (Oil World Statistics Update 1992). The European Community figure includes only the major producers Denmark, France, Germany, and U.K. and would be somewhat higher if smaller producers such as Italy and Spain were included. Because of its high yields, European Community was the leading producer of rapeseed oil in 1991.
Winter type B. napus is the main rapeseed crop in most of Europe, in parts of China and also in the eastern United States. Spring type B. napus is produced in Canada, northern Europe, and China. Where winters are mild enough (e.g. southeastern United States) spring type B. napus can be grown in the fall. In the future we should see distinct varieties developed for these areas.
Spring type B. rapa occupies approximately 50% of the Canadian rapeseed area and is also grown in northern Europe, China, and India. Winter type B. rapa has largely been replaced by more productive winter type B. napus and spring crops in its traditional production areas and has no significant impact on the world's rapeseed production at the present.
Only spring types exist of B. juncea. It is the leading Brassica oilseed in India and also produced in Canada and Europe but only for condiment use. Recently, low erucic, low glucosinolate types of B. juncea have been developed and it is possible that in the future it will be an important oilseed crop for the more arid areas of Canada and the northern United States.
The transition from high erucic to low erucic rapeseed, and the simultaneous rapid growth in the global rapeseed production began in Canada in 1968, with commercial release of single low cultivar 'Oro' followed by several other single low cultivars and the first canola Cultivar 'Tower' in 1974. In Europe, the transition started later with the release of the first single low cultivars in 1974. Almost all rapeseed produced in Canada and Europe is canola. The introduction of low erucic rapeseed is now underway in China and India.
This change in crop quality has created a need for specialized production of industrial rapeseed. Improved cultivars for this purpose have been developed in Canada, the United States and now in Europe. Because of the relatively small demand for high erucic oil and, consequently, for industrial rapeseed in comparison with edible rapeseed, most plant breeders now work exclusively on canola. This has led to a shortage of competitive new industrial rapeseed cultivars and, consequently, complicated industrial rapeseed production further.

Cultural and Environmental Requirements
Heat Tolerance

Rapeseed grows best in mild maritime climates. Historically, the highest rapeseed yields have been produced in England and the Netherlands, a phenomenon which has more to do with climate and soil conditions than sophisticated crop management.
The growth of rapeseed is most vigorous in temperatures between 10° and 30°C with the optimum around 20°C. Rapeseed is very sensitive to high temperatures at the blooming time even when ample moisture is available. Long periods of over 30°C can result in severe sterility and high yield losses. During the pod-filling period rapeseed is somewhat more tolerant to high temperatures. The seed oil content, however, is highest when the seeds mature under low temperatures (10° to 15°C). Extended periods of high temperature during the seed-fill period invariably result in low oil contents and poor seed quality.

Cold Tolerance

The rapeseed plant's ability to tolerate low temperatures depends essentially on its development and the degree of hardening it has achieved. Unhardened plants can survive -4°C, while fully-hardened spring type rapeseed can survive -10deg. to -12°C. Hardened winter rapeseed can survive short periods of exposure to temperatures between -15° and -20°C. Dehydration during sunny and/or windy days while the soil is frozen can cause extensive winter kill in much higher temperatures even when the plants are optimally developed and fully hardened.
The hardening requirements of rapeseed have not been fully characterized. Some time in temperatures below 10°C is, however, typically required. Winter types tend to harden faster, achieve higher degree of cold tolerance and unharden slower than spring types (Paul Raymer pers. commun.), but it is likely that variable hardening requirements could also be found within both types. Some differences in cold hardiness have been observed among both winter spring types. Whether these are due to differences in ultimate achievable cold hardiness or differences in hardening requirements only is unclear.
The plants are typically best adapted to survive the winter in rosette stage with 6 to 8 leaves. Smaller plants are usually not as capable of surviving over-wintering, while plants with more leaves often start the stem elongation prematurely, exposing the meristem tissue to cold, making it more susceptible to damage.
Unhardening happens fairly fast after the plants initiate active growth. Winter type rapeseed can generally still survive temperatures down to 12°C just before the blooming begins (Cramer 1990).
Winter survival is greatly reduced by environmental factors such as occurrence of diseases and pests, grazing, inadequate, excessive or unbalanced soil fertility, and poor drainage conditions. The absence of snow cover during the coldest period of the winter decreases the plants' chances to survive. Ice formation on the soil surface can damage the crown area of the plants and reduce survival rate.

Vernalization Requirement

Most winter rapeseed cultivars will require three weeks of near-freezing temperatures in the field to get fully vernalized and start rapid generative growth. In controlled environments, eight weeks at 4°C temperature is sufficient for full vernalization. In spring planting, winter rape will typically start slow generative growth after the prolonged rosette stage, and some cultivars may start blooming towards the end of the growing season. Differences in this respect are sometimes useful in distinguishing between similar cultivars. Differences in vernalization requirements are apparent among winter rape cultivars.
Some spring type cultivars do not exhibit any vernalization response at all, but in some cases the generative development can be accelerated with brief chilling treatment. In spring planting, only a few cool nights are usually needed for this. Vernalization response in spring types also tends to disappear in a long day environment (Raymer pers. commun.). In spite of the variability in vernalization requirements within both types, the differences between the types are fairly clear with no overlap in the initiation of blooming in either spring or fall planting.
A high vernalization requirement does not necessarily result in good winter hardiness, as many of the winter type cultivars from extreme maritime environments, such as Japan, require a long vernalization period yet have little tolerance for low temperatures.

Site Selection and Cultural Practices

Good drainage is an essential. Winter rape in particular has little tolerance for heavy, wet soils and a high water table. Wet soil can significantly reduce winter survival and contribute to root disease. Establishment of uniform stands is often difficult in heavy soils. Rapeseed grows best in sandy loams, loams with high organic matter, and loamy sands. Light soils are acceptable, and even ideal when adequate moisture and nutrients are available. Boron deficiency can cause significant yield losses even if no morphological deficiency symptoms are visible.

Utilization of the Product
Canola Oil

Well-developed rapeseed seed contains 40 to 44% oil. The fatty acid composition of the oil is genetically more variable than probably the composition of any other major vegetable oil. Canola oil today contains only traces of erucic acid, 5 to 8% of saturated fat, 60 to 65% of monounsaturated fats, and 30 to 35% of polyunsaturated fats. Mutants with significantly elevated monounsaturate levels exist.
Canola oil is widely used as cooking oil, salad oil, and making margarine. Of all edible vegetable oils widely available today, it has the lowest saturated fat content, making it appealing to health-conscious consumers. Its use in continuous frying and some other industrial uses is somewhat limited by its high linolenic acid (C18:3) content (usually 8 to 12%) and, consequent, fairly high oxidation tendency. Mutant materials with only 2 to 3% of linolenic have also been developed.
The use of canola oil in non-edible uses has been studied fairly extensively and it is at the present used to some extent in lubricants and hydraulic fluids especially when there is a significant risk of oil leaking to water ways or to ground water.

High Erucic Acid Rapeseed (HEAR) Oil

High erucic rapeseed oil is used in lubricants, especially where high heat stability is required. Because of its high polarity, uniform molecule size, and long carbon chains it has greater affinity to metal surfaces and better lubricity than mineral oils. It is easily biodegradable which makes it especially appealing in environmentally sensitive uses. Although HEAR oil in many applications is superior to vegetable oils with shorter average fatty acid chain length, such as canola, it can sometimes be replaced by these. The surplus of low erucic oil in European Community countries has especially increased industry's interest in Europe to use it in place of HEAR oil. This situation has also increased public interest in promoting the production of industrial rapeseed to lower the surpluses of low erucic rapeseed.
In the oleo-chemical, industry high erucic oil is used as a source of erucic acid to produce a slipping and anti-blocking agent used in plastic foils, foaming agents used for instance in mining industry, and many other chemicals for both food and non-food industries. The long chain length of erucic acid makes it a unique raw material in oleo chemical industry. Although in some oleo chemical processes it is virtually irreplaceable, the total demand for erucic acid is fairly low and not expected to grow radically in the near future. Most likely, growth rate is approximately equal with the general growth of oleo chemical industry, which again, as typical for mature industries, is likely to be approximately equal with the overall economic growth.
Significant changes to this scenario will depend on inventions and technical breakthroughs which defy prediction. There is, however, a trend visible that is likely to work in favor of increased use of high erucic oil in future, both in oleo chemical and other uses. The development of "green technology" with increased emphasis on renewable resources and biodegradability is likely to increase interest in raw materials such as high erucic oil.

Rapeseed Meal

Rapeseed meal contains approximately 40% of protein which rates among the nutritionally best plant proteins. For monogastric diets it has better amino acid balance than soybean meal.
In traditional rapeseed cultivars the seed solids contained over 100 µmol/g of glucosinolates. The hydrolysis products of glucosinolates give cruciferous vegetables their characteristic flavor and mustard it's pungency. Some of these hydrolysis products, however, are toxic or at least anti-nutritional. Also, many of the glucosinolate derivatives decrease the palatability of the meal and, consequently, the voluntary uptake of the feed by animals. For these reasons, the use of conventional rapeseed meal was limited mainly to cattle supplementary protein formulas and had relatively low value.
With the quality of canola, significant amounts of meal can be used in virtually all animal feeds and economical disposal of the crushing residue is typically not a problem. Since some of the glucosinolates are destroyed in the crushing process, the meal of future canola cultivars will be almost glucosinolate free and can be used in feed formulas without any special limitations.