Plant Breeding and Biotechnology Agriculture precipitated urbanization around 10 000 years ago Population size increased and became more sedentary with abundance of food Properties of previously wild animal and plant species were changed by breeding Plant Breeding and Biotechnology Breeding is artificial selection Reproductive success is controlled by people instead of natural processes Plant Breeding and Biotechnology Maize vs Teosinte Teosinte grows in the wild Mexico Nicaragua Plant Breeding and Biotechnology Teosinte husk Tiny hard kernels Each row of kernels surrounded by a thick Plant Breeding and Biotechnology Teosinte of seeds Kernels come loose at maturity for dispersal Plant Breeding and Biotechnology Maize Giant sweet kernels Kernels stay attached to cob Husk envelopes whole cob not individual rows Plant Breeding and Biotechnology Crops and Humans as a mutualistic interaction Domesticated Plants get Seed dispersal Protection from competitors Population explosion But they give up Ability to survive without humans Plant Breeding and Biotechnology Crops and Humans as a mutualistic interaction Humans get Steady source of calories Sedentary life styles specialist members of society cities population explosion But give up independence Plant Breeding and Biotechnology Breeding in a small nutshell Two individuals with different properties mate The offspring show variation mixing and matching the properties of the parents Human selection of the favored offspring Repeat Plant Breeding and Biotechnology Requirements for breeding Interfertile individuals Same species or very closely related species Offspring need to be viable as well Variation between the individuals Plant Breeding and Biotechnology Breeding works by scrambling genes into new combinations followed by selection Imagine two individuals of a fruit species Big Poisonous Small Tasty one gene Big small controlled by different versions of Poisonous tasty controlled by different versions of another gene Plant Breeding and Biotechnology Breeding works by scrambling genes into new combinations followed by selection Big poisonous mates with small tasty Genes scramble in offspring Big poisonous Small tasty Small poisonous Big tasty Select the offspring with the best combination of traits and repeat Plant Breeding and Biotechnology Often traits good for agriculture are bad for plant s survival Big and tasty too much energy into sugars not enough to pathogen defense Modern breeding often employs crosses between wild relatives of crops with domesticated crops Plant Breeding and Biotechnology Freaks created by breeding Maize from teosinte Plant Breeding and Biotechnology Freaks created by breeding Lots of crops from wild mustard Plant Breeding and Biotechnology Freaks created by breeding Dogs from wolves Plant Breeding and Biotechnology Modern era 1 We know that genes are sections of DNA which encode a specific protein 2 We have the sequence for lots of DNA 3 For many genes we understand how the encoded protein works Plant Breeding and Biotechnology Semi dwarf rice variety IR8 Shorter plants less prone to wind damage and produce higher yields Results from mutation in a gene which encodes a Gibberellin biosynthesis enzyme The mutant gene was bred into many rice varieties using artificial selection Responsible for saving millions of lives Sasaki et al 2002 Nature 416 701 Plant Breeding and Biotechnology Modern era 1 We know that genes are sections of DNA which encode a specific protein 2 We have the sequence for lots of DNA 3 For many genes we understand how the encoded protein works 4 Recombinant DNA can easily be made fusion of DNA from different sources 5 Recombinant DNA can be inserted into the chromosomes of plants Transgenic or Genetically Modified plants Plant Breeding and Biotechnology Inserting DNA with the Agrobacterium tumefacians Ti plasmid Plant Breeding and Biotechnology Similarities with breeding Scrambles genes in new combinations to change plant traits Differences with breeding Requires specific knowledge what does the new gene protein do How will that lead to the desired trait Crosses species barrier For instance bacterial gene expressed in plants Plant Breeding and Biotechnology Bt An example Bacillus thuringiensis A soil bacterium Produces a protein which is toxic to many insects the Bt toxin The bacteria itself or the purified toxin has been used as a pesticide since the 1920 s An organic pesticide which readily breaks down in the environment Very specific for insects for instance Bt toxin is sprayed from helicopters to control local gypsy moth outbreaks Plant Breeding and Biotechnology Bt An example The DNA which codes for the Bt toxin has been inserted into many crop plants Bt Maize and cotton are widely planted in the US Instead of spraying the bacteria the plants themselves make the toxin Allows increased yields and drastic reductions in synthetic pesticides Plant Breeding and Biotechnology Bt An example Crops themselves regulated as pesticides by US EPA Food products like all other food products regulated tested by the US FDA Plant Breeding and Biotechnology Glyphosate resistance a second common example An enzyme called EPSP synthetase is required to make aromatic amino acids Humans and other animals do not have EPSP synthetase we need to obtain these essential amino acids from our diets Glyphosate destroys the function of EPSP synthetase in plants a systemic herbicide Does not affect humans or other animals Rapidly degrades in the environment Plant Breeding and Biotechnology Glyphosate resistance a second common example Bacterial EPSP synthetase is not affected by glyphosate Plants engineered to contain the bacterial EPSP synthetase are unaffected by glyphosate treatment Most US soy is Roundup ready glyphosate resistant Plant Breeding and Biotechnology Golden rice Starchy endosperm makes up most of the rice grain Very little carotene No natural rice varieties can synthesize carotene in the endosperm Plant Breeding and Biotechnology Golden rice Three genes engineered to function in rice endosperm Each gene makes an enzyme in the carotene biochemical pathway Made by government funded public research freely available for conventional breeding programs Plant Breeding and Biotechnology An interesting experiment North America vs rest of world Almost all transgenic crops are grown in USA Brazil and Canada 80 of soy 60 of maize 90 of cotton in US 75 of all processed foods have at least one transgenic derived