The Biology of Triticum aestivum L. (Bread Wheat)



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The Biology of
Triticum aestivum L.

(Bread Wheat)

this is a picture of wheat in a field.

Picture credit: Wikimedia Commons

Version 3 January 2016

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.

This document has been updated from Version 2 (February 2008) and includes an appendix containing a weed risk assessment of wheat volunteers based on the National Post-Border Weed Risk Management Protocol.

For information on the gene technology regulation visit the OGTR website.

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Table of Contents



Preamble 4

Section 1 Taxonomy 4

Section 2 Origin and Cultivation 7

2.1 Centre of diversity and domestication 7

2.2 Commercial uses 7

2.3 Cultivation in Australia 8



2.3.1 Commercial propagation 9

2.3.2 Scale of cultivation 9

2.3.3 Cultivation practices 10

2.4 Crop Improvement 16



2.4.1 Breeding 16

2.4.2 Genetic modification 17

Section 3 Morphology 17

3.1 Plant morphology 17



3.1.1 The stem 17

3.1.2 The leaf 18

3.1.3 Tillers 18

3.1.4 The roots 19

3.2 Reproductive morphology 19



3.2.1 The ear 19

3.2.1 The caryopsis 19

Section 4 Development 20

4.1 Reproduction 20

4.2 Pollination and pollen dispersal 20

4.3 Fruit/seed development and seed dispersal 21

4.4 Seed dormancy, germination, seed banks and persistence 23

4.4.1 Dormancy and germination 23

4.4.2 Seed banks and persistence 25

4.5 Vegetative growth 26



4.5.1 Root development 27

4.5.2 Leaf development 27

4.5.3 Stem development 27

4.5.4 Tiller development 27

Section 5 Biochemistry 28

5.1 Toxins 28

5.2 Allergens 28

5.2.1 Dust and flour allergies 28

5.2.2 Coeliac disease 28

5.3 Other undesirable phytochemicals 29



5.3.1 Enzyme inhibitors 29

5.3.2 Lectins 29

5.3.3 Phytic acid 29

5.3.4 Nitrate poisoning 29

5.4 Beneficial phytochemicals 30



Section 6 Abiotic Interactions 31

6.1 Abiotic stress limiting growth 31



6.1.1 Nutrient stress 31

6.1.2 Temperature and water stress 31

6.1.3 Salt stress 31

6.2 Abiotic tolerances 32



Section 7 Biotic Interactions 32

7.1 Weeds 32

7.2 Pests and pathogens 32

7.2.1 Vertebrate pests 32

7.2.2 Invertebrate pests 33

7.2.3 Pathogens 33

7.3 Other biotic interactions 35



Section 8 Weediness 36

8.1 Weediness status on a global scale 36

8.2 Weediness status in Australia 36

8.3 Weediness in agricultural ecosystems 36

8.4 Weediness in natural ecosystems 37

8.5 Control measures 37

8.6 Weed risk assessment of wheat 37

Section 9 Potential for Vertical Gene Transfer 38

9.1 Intraspecific crossing 39

9.2 Natural interspecific crossing 40

9.3 Natural intergeneric crossing 40

9.4 Artificial interspecific and intergeneric crossing 43

References 45




Preamble


This document describes the biology of Triticum aestivum L. (bread wheat), with particular reference to the Australian environment, cultivation and use. Information included relates to the taxonomy and origins of cultivated T. aestivum, general descriptions of its morphology, reproductive biology, development, biochemistry, 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 in risk assessments of genetically modified T. aestivum that may be released into the Australian environment.

In Australia, the majority of wheat grown is T. aestivum and its cultivars. The other wheat species grown in Australia is Triticum turgidum subsp. durum (Desf.) Husn., also known as durum or pasta wheat. The terms ‘wheat’ and ‘bread wheat’ will be used as general terms to refer to T. aestivum throughout this document.

Bread wheat is an annual grass generally grown in Australia as a rotation crop. The varieties grown in Australia are spring wheat varieties although they are grown during the winter growing season and harvested in early summer. Bread wheat is the most widely grown food crop in the world and Australia is one of the four major exporters of wheat in the world.

Worldwide, two species of wheat are commonly grown. The first, T. aestivum, or bread wheat, includes the classes hard ‘red winter’, ‘hard red spring’, ‘soft red winter’, ‘hard white’ and ‘soft white’. The second, T. turgidum subsp. durum, includes the ‘durum’ and ‘red durum’ wheat classes (macaroni or pasta wheats). In Australia, production is limited to these two types. Bread wheat grown in Australia is exclusively white and does not have the red colour typical for most bread wheat grown in the northern hemisphere.


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