This document provides an overview of baseline biological information relevant to risk assessment of genetically modified forms of the species that may be




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The Biology of
Brassica napus L. (canola)






Version 2: February 2008


This document provides an overview of baseline biological information relevant to risk assessment of genetically modified forms of the species that may be released into the Australian environment. Cover photo courtesy of Brian Weir.


For information on the Australian Government Office of the Gene Technology Regulator visit

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Table of Contents


Preamble

Section 1 Taxonomy

Section 2 Origin and cultivation

2.1 Centre of diversity and domestication

2.2 Commercial uses

2.3 Cultivation in Australia

2.3.1 Commercial propagation

2.3.2 Scale of cultivation

2.3.3 Potential for expansion of the Canola growing region

2.3.4 Cultivation practices

2.4 Crop Improvement

2.4.1 Breeding

2.4.2 Genetic modification

Section 3 Morphology

3.1 Plant morphology

3.2 Reproductive morphology

Section 4 Development

4.1 Reproduction

4.2 Pollination and pollen dispersal

4.2.1 Pollen characteristics

4.2.2 Pollen movement

4.2.3 Pollen viability

4.3 Fruit/seed development and seed dispersal

4.3.1 Fruit and seed development

4.3.2 Seed dispersal

4.4 Seed dormancy and germination

4.4.1 Viability/germination

4.4.2 Dormancy

4.4.3 Seed banks/persistence

4.5 Vegetative growth

Section 5 Biochemistry

5.1 Toxins

5.2 Allergens

5.3 Other undesirable effects of phytochemicals

5.4 Beneficial phytochemicals

Section 6 Abiotic Interactions

6.1 Abiotic stresses

6.1.1 Nutrient stress

6.1.2 Temperature stress

6.1.3 Water stress

Section 7 Biotic Interactions

7.1 Weeds

7.2 Pests and pathogens

7.2.1 Pests

7.2.2 Diseases

Section 8 Weediness

8.1 Weediness status on a global scale

8.2 Weediness status in Australia

8.2.1 Cultivated areas

8.2.2 Non-cropped disturbed habitats

8.2.3 Undisturbed natural habitats

8.3 Control measures

Section 9 Potential for Vertical Gene Transfer

9.1 Intraspecific crossing

9.2 Interspecific crossing

9.2.1 Brassica rapa

9.2.2 Brassica juncea

9.2.3 Brassica oleracea

9.3 Intergeneric crossing

9.3.1 Tribe Brassiceae species 37

9.3.2 Other plant species 42

References

Preamble

This document describes the biology of canola (Brassica napus L.) with particular reference to the Australian environment, cultivation and use. Information included relates to the taxonomy and origins of cultivated B. napus, general descriptions of its morphology, reproductive biology, biochemistry, and biotic and abiotic interactions. This document also addresses the potential for gene transfer to occur to closely related species. The purpose of this document is to provide baseline information about the parent organism for use in risk assessments of genetically modified canola that may be released into the Australian environment.


The term ‘canola’ refers to those varieties1 that meet specific standards on the level of erucic acid and glucosinolates. The word ‘canola’ is derived from ‘Canadian oil, low acid’ and was registered in Canada in 1970. The canola name is now used for three Brassica species: B. napus also known as ‘Argentine variety’, B. rapa also known as ‘Polish variety’ and B. juncea or mustard. Canola has been grown in Australia since 1969, however, rapeseed or oilseed rape (also B. napus), which did not meet the current canola standards, had been grown in Australia from the early 1960’s. Canola is grown primarily for its seeds, which yield between 35 % to over 45 % oil. Its main use is as cooking oil, but it is also commonly used in margarine. Canola meal is produced as a by-product during extraction of oil from canola seed and is widely used as a high protein feed source in animal nutrition.


Section 1 Taxonomy

The Brassicaceae family (formerly Cruciferae) consists of approximately 375 genera and 3200 species of plants, of which approximately 52 genera and 160 species are present in Australia (Jessop & Toelken 1986). Of the 160 species of Brassicaceae present in Australia, several species are important weeds of the southern Australian cropping zone. Genera of economic importance in Australia are Brassica as a crop and Raphanus, Sinapis, and Brassica as weeds. In Australia, other important cropping weeds from the Brassicaceae family include Hirschfeldia incana, Diplotaxis spp. and Sisymbrium spp. (Rieger et al. 1999).


The Brassica genus consists of approximately 100 species, including species Brassica napus L., spp. oleifera, commonly known as oilseed rape, rapeseed or canola. B. napus is not native to Australia, and originated in either the Mediterranean area or Northern Europe. It is thought to have originated from a cross where the maternal donor was closely related to two diploid species, B. oleracea and B. rapa (OECD 1997).


The botanical relationship between the Brassica oilseed species was first established as a result of taxonomic studies carried out in the 1930s (U 1935) (Fig 1). It was proposed that the three species with higher chromosome numbers, B. juncea, B. napus and B. carinata, are amphidiploids (double the number of chromosomes) derived from the diploid species, B. nigra (L.) Koch, B. rapa (syn B. campestris) and B. oleracea L.


The cytogenetic relationships of Brassica species show that:

  • B. carinata is an amphidiploid (BBCC2, n=17) probably arising from B. oleracea (CC, n=9) and B. nigra (BB, n=8);

  • B. napus is an amphidiploid (AACC, n=19) of B. oleracea and B. rapa (AA, n=10), and

  • B. juncea is an amphidiploid (AABB, n=18) of B. rapa and B. nigra.


The cytogenetic relationship between the Brassica species established by (U 1935) was later confirmed by chromosome pairing and artificial synthesis of amphidiploids, nuclear DNA content, DNA analysis and the use of genome-specific chromosome markers. Although it was proposed that the three diploid species have originated from one common ancestor, recent molecular investigations indicate a common origin for B. rapa and B. oleracea, with B. nigra having evolved from a separate progenitor (Paterson et al. 2006; Sabharwal et al. 2006)




















Fig.1 Genomic relationship of main cultivated Brassica species.


Section 2 Origin and cultivation

2.1 Centre of diversity and domestication

Brassica napus was cultivated by ancient civilisations in Asia and the Mediterranean. Its use has been recorded as early as 2000BC in India (Colton & Potter 1999) and has been grown in Europe since the 13th century, primarily for its use as oil for lamps (Colton & Sykes 1992). B. napus was first grown commercially in Canada in 1942 as a lubricant for use in war ships. It was first grown commercially in Australia in 1969.


Traditionally, in western countries, B. napus was considered unsuitable as a source of food for either humans or animals, because the seed naturally contains erucic acid and glucosinolates, which are toxic to humans and other organisms (see Section 5). However, it was widely used as an edible oil in Asia for thousands of years (OECD 1997). In the 1970s, very intensive breeding programs in several countries including Australia produced high quality varieties that were significantly lower in these two toxicants. The term ‘canola’ refers to those varieties of B. napus that meet specific standards on the level of erucic acid and glucosinolates. These varieties must yield oil low in erucic acid and meal low in glucosinolates and are often referred to as double low varieties.

2.2 Commercial uses

Canola has become more important to the western world, through breeding for better oil quality and improved processing techniques (OECD 1997). Edible oil was first extracted in Canada in 1956 (Colton & Potter 1999). Canola is now grown primarily for its seeds, which yield between 35 % to over 45 % oil. Its main used is as cooking oil, but it is also commonly used in margarine. Although normally grown as an oilseed crop, it may be profitable for canola to be cut for hay in spring if demand is high (Pritchard et al. 2007).


Canola meal is produced as a by-product during the extraction of oil from canola seed and is widely used as a high protein feed source in animal nutrition. Full fat canola seed may also be used directly as animal feed (Roth-Maier 1999). Industry standards require canola meal to be low in glucosinolates (total glucosinolates of 30 μmoles g-1) in toasted oil free meal (OECD 2001). The maximum level for erucic acid is 2% in the oil fraction (CODEX 2001). Note that oil from varieties of B. rapa or B. juncea, which also meet these standards, may also be referred to as canola.

2.3 Cultivation in Australia

2.3.1 Commercial propagation

Canola reproduction is through seed production. Generally seeds of a canola variety can be saved and used to plant subsequent crops, with the exception of hybrid canola (see Section 2.4.2). However, saving seed can result in poor seed viability and establishment failure in subsequent crops. Outcrossing in canola can result in slight genetic change from year to year and considerable change over a number of years. Experiments have shown that over time, farmer-retained seed can have reduced oil quality, yield and other agronomic performance (Marcroft et al. 1999).


Canola seed of high varietal or genetic purity is produced following a seed certification scheme based on the Rules and Directives of the OECD Seed Schemes and International Seed Testing Association (ITSA) (Smith & Baxter 2002). There are two main production classes for pure seed, either certified or basic seed. The production of basic seed requires an isolation of 200 m from other varieties or any other Brassica or cruciferous crop or weed species. Additionally, the land used for basic seed production must not have grown or been sown to canola or another Brassica or Cruciferous crop species for the previous five years, unless it was the same variety or certification class. The production of certified seed requires an isolation distance of only 100 m and the same land use restrictions as for basic seed production, but only extending for the previous three years. Seed must be at least 99% pure (by mass), have a minimum germination of 85% (by count) and contain no more than 20 other seeds per kg (Smith & Baxter 2002).

2.3.2 Scale of cultivation

Canola production grew significantly in Australia from approximately 100,000 ha in the early 1990s to an estimated total area of 1.4 Mha in 2000 (Colton & Potter 1999). The five year average (to 2004/2005) area planted to canola was 1.335 Mha, with an average production of 1529 kt. Typically 400 to 500 kt are used domestically, nearly all of this is crushed for oil production, with seed production accounting for 5 to 6 kt (ABARE 2007). Current production estimates for the 2007/8 crop year are for 1399 kt (ABARE 2007). Internationally, production by the largest producers in 2004, was Australia 1.55, United Kingdom 1.61, Poland 1.63, France 3.97, Germany 5.23, Canada 7.73, and China 13.18 million tonnes (FAO 2006). Australia accounts for < 5% of the world’s canola production, but it is second only to Canada as an exporter of canola seed (Carr 2005).


Canola occupies approximately 6 % of the cropped area in New South Wales, Victoria, South Australia and Western Australia (Norton et al. 1999) and these states account for more than 99% of Australia’s total canola production (based on the 5 year average to 2004/2005) (ABARE 2007). Production in Australia by state was 38% WA, 22% NSW, 22% Victoria, and 17% SA (based on the 4 year average to 2005/006). Total production over this 4 year period was 5,383,000 tonnes on 4,056,000 ha, for an average of 1.327 tonne per ha (AOF 2007b).


In Australia, canola is an established crop in the medium and high rainfall (400 mm and above) areas of southern Australia, which represents the winter production cereal belt (see Table 1, Figure 2). However the development of early maturing varieties is expanding growing areas of canola into the low rainfall areas of the wheat belt.

Table 1. Climatic/soil type data for areas where canola is grown




Wagga

Wagga

(NSW)

Hamilton

(VIC)

Mt Gambier (SA)

Minnipa

(SA)

Merredin

(WA)Average daily max/min temperaturea at planting (April-May)19.9°C/7.5°C17.2°C/7.8°C17.8°C/8.0°C17.1°C/10.7°C22.9°C/10.9°CAverage daily max/min temperature (winter)13.6°C/3.3°C12.6°C/4.9°C13.7°C/5.4°C16.7°C/6.8°C16.9°C/5.9°CAverage daily max/min temperature (spring)21.3°C/7.8°C17.9°C/8.6°C18.5°C/8.0°C23.9°C/10.1°C24.4°C/9.7°CAverage Annual rainfall568.4 mm686.7 mm774.9 mm327.3 mm327.3 mmRainfall May-November

(% of Annual Rainfall)363.9 mm

(64%)481.7 mm

(70%)574.0 mm

(74%)244.5 mm

(75%)239.8 mm

(73%)Soil type reddish sandy loamAcid basaltic clayVolcanic sands/ sandy loamreddish brown sandy loam, highly alkaline Red-brown sandy loam to sandy clay loama Temperature and rainfall from Bureau of Meteorology: http://www.bom.gov.au/climate/averages/

Each state has an appropriate government agency (eg Department of Primary Industry), which tests and recommends varieties suitable to the canola growing regions of the state. For example, the “2005 Crop Variety Sowing Guide for Western Australia” lists characteristics of 41 major canola varieties comprising 14 triazine tolerant, 7 imidazolinone–tolerant, 16 conventional and 3 hybrid varieties, for the grainbelt of WA. Variety characteristics include flowering class (early to late), height, blackleg resistance, oil content and suitability for various rainfall zones. Information on new canola varieties being trialled in Australia can be found at the National Variety Trial – Online website (NVT Online 2007).

2.3.3 Potential for expansion of the Canola growing region

Canola has been grown in northern NSW and southern Qld, reaching approximately 15,000 ha in the early 1990s, but then due to frost damage and several drought years the area declined. The problems facing canola production in this area were reported to be variable climatic conditions (particularly frost during early pod filling), poorly adapted varieties, poor establishment and inadequate nutrition. Growers’ perception was that canola was poorly adapted to these northern areas and it was noted that canola suppressed establishment and growth of subsequent sorghum and other summer crops. However, a decade later canola production had risen to 25-30,000 ha (most of this in NSW) – due to increased grower experience and greater variety choice, which allowed a reduction in the risk of frost loss at flowering time. Limitations to further canola increases for this area were identified as the need to design methods of harvest management to overcome large harvest losses (up to 90%) and the distance to market. (Holland et al. 2001)


Further expansion of up to 150,000 ha in northern NSW and an additional 50,000 to 175,000 ha in southern Queensland may be possible through the introduction of improved canola and Indian mustard varieties with higher oil contents, virus tolerance in mustard, a better understanding of nutritional requirements and reaction to frost, and rotation implications for following summer crops or winter cereals. A strong desire to have more rotation crops to help overcome crown rot and other disease problems in wheat is one of the main motivators for expansion of canola an/or Indian mustard in these areas. (GRDC 2007b)


Canola has typically been grown in areas of at least 450 mm rainfall in WA, but experience in WA has shown that canola can also be grown profitably in the lower rainfall (approximately 325 mm) areas of the northern grainbelt (Carmody & Cox 2001) Profitability depended upon a number of interrelated factors; the most limiting being the timing of opening rainfall and high temperature during pod fill. Other factors

included weed competition, soil acidity, fertiliser timing, blackleg disease, insect pests and harvest management. Managing the main limiting factors were the key to profitable canola production in the northern grainbelt of WA (Carmody & Cox 2001).


Canola has not been grown commercially in the Northern Territory (NT) but has recently been trialled at the Katherine Research Station as one of nine crops to identify bio-fuel crops agronomic adaptation to the area. These crops, including canola, were selected because they had either never been grown in the NT, or on clay loam soils or established under dry season irrigated conditions in Katherine (Bennett et al. 2006).



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