The Biology of Gossypium hirsutum L. and Gossypium barbadense L. (cotton) Version 2.1 April 2013 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. Version 2 (February 2008) has been updated to include an appendix containing a weed risk assessment of cotton based on the National Post-Border Weed Risk Management Protocol. References to the new appendix have been added in the text. Minor updates to the sections on seed dispersal, out-crossing rates and commercial production of GM cotton have also been made. For information on the Australian Government Office of the Gene Technology Regulator visit <http://www.ogtr.gov.au> The Biology of Gossypium hirsutum & G. barbadense (cotton) Office of the Gene Technology Regulator TABLE OF CONTENTS PREAMBLE ............................................................................................................................... 1 SECTION 1 TAXONOMY ........................................................................................................ 1 1.1 TAXONOMY AND DISTRIBUTION OF NATIVE AUSTRALIAN COTTON SPECIES ................. 3 SECTION 2 ORIGIN AND CULTIVATION ............................................................................ 4 2.1 CENTRE OF DIVERSITY AND DOMESTICATION............................................................. 4 2.2.1 Origin in Australia..................................................................................... 6 2.2 COMMERCIAL USES .................................................................................................. 6 2.3 CULTIVATION IN AUSTRALIA .................................................................................... 8 2.3.1 Commercial propagation ........................................................................... 8 2.3.2 Scale of cultivation .................................................................................... 8 2.3.3 Cultivation practices ................................................................................ 13 2.4 CROP IMPROVEMENT.............................................................................................. 15 2.4.1 Breeding .................................................................................................. 15 2.4.2 Genetic modification ................................................................................ 16 SECTION 3 MORPHOLOGY................................................................................................. 17 3.1 PLANT MORPHOLOGY ............................................................................................. 17 3.2 REPRODUCTIVE MORPHOLOGY ............................................................................... 19 SECTION 4 DEVELOPMENT................................................................................................ 20 4.1 REPRODUCTION ..................................................................................................... 20 4.1.1 Asexual reproduction ............................................................................... 20 4.1.2 Sexual reproduction ................................................................................. 21 4.2 POLLINATION AND POLLEN DISPERSAL .................................................................... 22 4.2.1 Pollen ...................................................................................................... 22 4.2.2 Pollination............................................................................................... 23 4.2.3 Out-crossing rates ................................................................................... 23 4.3 FRUIT/SEED DEVELOPMENT AND SEED DISPERSAL .................................................... 26 4.3.1 Fruit development .................................................................................... 26 4.3.2 Seed dispersal.......................................................................................... 27 4.4 SEED DORMANCY AND GERMINATION ..................................................................... 29 4.4.1 Seed dormancy ........................................................................................ 29 4.4.2 Germination ............................................................................................ 30 4.4.3 Seedling survival ..................................................................................... 31 4.5 VEGETATIVE GROWTH............................................................................................ 31 SECTION 5 BIOCHEMISTRY ............................................................................................... 31 5.1 TOXINS .................................................................................................................. 31 5.1.1 Gossypol ................................................................................................. 32 5.1.2 Cyclopropenoid Fatty Acids ..................................................................... 33 5.2 ALLERGENS ........................................................................................................... 34 5.3 BENEFICIAL PHYTOCHEMICALS ............................................................................... 34 5.3.1 Medicines ................................................................................................ 34 5.3.2 Stock feed ................................................................................................ 35 SECTION 6 ABIOTIC INTERACTIONS............................................................................... 35 6.1 NUTRIENT REQUIREMENTS ..................................................................................... 35 6.2 TEMPERATURE REQUIREMENTS AND TOLERANCES ................................................... 37 6.3 WATER USE ........................................................................................................... 37 6.4 OTHER TOLERANCES .............................................................................................. 38 SECTION 7 BIOTIC INTERACTIONS ................................................................................. 39 7.1 WEEDS .................................................................................................................. 39 7.1.1 Weed Control .......................................................................................... 39 7.2 PESTS AND PATHOGENS .......................................................................................... 40 7.2.1 Pests........................................................................................................ 40 7.2.2 Pathogens................................................................................................ 43 iii The Biology of Gossypium hirsutum & G. barbadense (cotton) Office of the Gene Technology Regulator 7.3 OTHER INTERACTIONS ............................................................................................ 45 SECTION 8 WEEDINESS ....................................................................................................... 46 8.1 WEEDINESS STATUS ON A GLOBAL SCALE ................................................................ 46 8.2 WEEDINESS STATUS IN AUSTRALIA ......................................................................... 46 8.3 WEEDINESS IN AGRICULTURAL ECOSYSTEMS........................................................... 47 8.4 WEEDINESS IN NATURAL ECOSYSTEMS .................................................................... 47 8.5 CONTROL MEASURES ............................................................................................. 48 8.6 WEED RISK ASSESSMENT OF COTTON ...................................................................... 49 SECTION 9 POTENTIAL FOR VERTICAL GENE TRANSFER ........................................ 50 9.1 INTRASPECIFIC CROSSING ....................................................................................... 50 9.2 NATURAL INTERSPECIFIC AND INTERGENERIC CROSSING .......................................... 50 9.2.1 Crosses between G. barbadense and G. hirsutum ..................................... 50 9.2.2 Crosses with native Gossypium spp .......................................................... 51 9.3 CROSSING UNDER EXPERIMENTAL CONDITIONS ....................................................... 52 9.3.1 Cross-pollination with G- and K-genome natives ...................................... 52 9.3.2 Cross-pollination with C-genome natives ................................................. 53 9.3.3 Cross-pollination with other plant taxa .................................................... 55 REFERENCES ............................................................................................................................. 56 APPENDIX A WEEDS OF COTTON ....................................................................................... 85 APPENDIX B WEED RISK ASSESSMENT OF COTTON ...................................................... 86 iv The Biology of Gossypium hirsutum & G. barbadense (cotton) Office of the Gene Technology Regulator PREAMBLE This document describes the biology of Gossypium hirsutum (upland cotton) and Gossypium barbadense (pima cotton), with particular reference to the Australian environment, cultivation and use. Information included relates to the taxonomy and origins of cultivated G. hirsutum and G. barbadense, general descriptions of their morphology, reproductive biology,