The Biology of Triticum aestivum L. em Thell. (Bread Wheat) Picture reproduced from <http://www.acpfg.com.au/files/education/factsheets/wheat_barley_book.pdf> with permission from the Australian Centre for Plant Functional Genomics. 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. For information on the Australian Government Office of the Gene Technology Regulator visit <http://www.ogtr.gov.au> The Biology of Triticum aestivum L. em Thell. (bread wheat) Office of the Gene Technology Regulator TABLE OF CONTENTS PREAMBLE ...........................................................................................................................................1 SECTION 1 TAXONOMY..............................................................................................................1 SECTION 2 ORIGIN AND CULTIVATION................................................................................2 2.1 CENTRE OF DIVERSITY AND DOMESTICATION................................................................2 2.2 COMMERCIAL USES .......................................................................................................5 2.3 CULTIVATION IN AUSTRALIA ........................................................................................6 2.3.1 Commercial propagation ...............................................................................6 2.3.2 Scale of cultivation.........................................................................................6 2.3.3 Cultivation practices ......................................................................................8 2.4 CROP IMPROVEMENT.....................................................................................................9 2.4.1 Breeding .........................................................................................................9 2.4.2 Genetic modification ....................................................................................11 SECTION 3 MORPHOLOGY......................................................................................................12 3.1 PLANT MORPHOLOGY..................................................................................................12 3.1.1 The Stem.......................................................................................................12 3.1.2 The Leaf........................................................................................................13 3.1.3 Tillers ...........................................................................................................13 3.1.4 The Roots......................................................................................................13 3.2 REPRODUCTIVE MORPHOLOGY....................................................................................13 3.2.1 The Ear.........................................................................................................13 3.2.1 The Caryopsis...............................................................................................14 SECTION 4 DEVELOPMENT.....................................................................................................14 4.1 REPRODUCTION...........................................................................................................14 4.1.1 Sexual reproduction .....................................................................................14 4.2 POLLINATION AND POLLEN DISPERSAL........................................................................14 4.3 FRUIT/SEED DEVELOPMENT AND SEED DISPERSAL.......................................................16 4.4 SEED DORMANCY AND GERMINATION .........................................................................17 4.5 VEGETATIVE GROWTH ................................................................................................19 4.5.1 Root development .........................................................................................19 4.5.2 Leaf development..........................................................................................19 4.5.3 Stem development.........................................................................................20 4.5.4 Tiller development........................................................................................20 SECTION 5 BIOCHEMISTRY....................................................................................................20 5.1 TOXINS........................................................................................................................20 5.2 ALLERGENS.................................................................................................................20 5.2.1 Coeliac Disease............................................................................................21 5.3 OTHER UNDESIRABLE PHYTOCHEMICALS ....................................................................21 5.3.1 Enzyme inhibitors.........................................................................................21 5.3.2 Lectins ..........................................................................................................21 5.3.3 Phytic acid....................................................................................................22 5.3.4 Nitrate poisoning..........................................................................................22 5.4 BENEFICIAL PHYTOCHEMICALS ...................................................................................22 SECTION 6 ABIOTIC INTERACTIONS...................................................................................24 6.1 ABIOTIC STRESS LIMITING GROWTH ............................................................................24 6.1.1 Nutrient stress ..............................................................................................24 6.1.2 Temperature stress .......................................................................................24 6.1.3 Water stress..................................................................................................24 6.2 ABIOTIC TOLERANCES.................................................................................................25 iii The Biology of Triticum aestivum L. em Thell. (bread wheat) Office of the Gene Technology Regulator SECTION 7 BIOTIC INTERACTIONS......................................................................................25 7.1 WEEDS ........................................................................................................................25 7.2 PESTS AND PATHOGENS...............................................................................................25 SECTION 8 WEEDINESS ............................................................................................................26 8.1 WEEDINESS STATUS ON A GLOBAL SCALE ...................................................................28 8.2 WEEDINESS STATUS IN AUSTRALIA.............................................................................28 8.3 WEEDINESS IN AGRICULTURAL ECOSYSTEMS ..............................................................28 8.4 WEEDINESS IN NATURAL ECOSYSTEMS .......................................................................29 8.5 CONTROL MEASURES ..................................................................................................29 SECTION 9 POTENTIAL FOR VERTICAL GENE TRANSFER ..........................................29 9.1 INTRASPECIFIC CROSSING............................................................................................29 9.2 NATURAL INTERSPECIFIC AND INTERGENERIC CROSSING ............................................30 9.3 CROSSING UNDER EXPERIMENTAL CONDITIONS ..........................................................31 REFERENCES .....................................................................................................................................34 iv The Biology of Triticum aestivum L. em Thell. (bread wheat) Office of the Gene Technology Regulator PREAMBLE This document describes the biology of Triticum aestivum L. em Thell. (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 ssp. durum L, also know as durum or pasta wheat. The terms ‘wheat’ and ‘bread wheat’ will be used as general terms to refer to T. aestivum. 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. SECTION 1 TAXONOMY Triticum aestivum L. em Thell. is recorded