Chapter 9 - Improving Plants PDF

10/7/2014 Chapter 9—Improving Plants Key Concepts Chromosomes control inheritance Mendel’s laws are the basis of plant breeding Sexually reproducing plants are self‐ or cross‐ pollinated Collection, selection, crossing, evaluation, and introduction are the main steps of breeding Gene transformation...

10/7/2014 Chapter 9—Improving Plants Key Concepts Chromosomes control inheritance Mendel’s laws are the basis of plant breeding Sexually reproducing plants are self‐ or cross‐ pollinated Collection, selection, crossing, evaluation, and introduction are the main steps of breeding Gene transformation allows transfer of one or several genes Crop Improvement Fundamental aspect of development of modern agriculture Significant advances during twentieth century due to rediscovery of Mendel’s principles Half Half of yield gains in major cereal crops are a result of genetic improvement Agricultural biotechnology—scientific techniques used to create or transform plants · Yield-how much is produced of something/crop) 1 10/7/2014 Corn Yield 1900 to Present - U.S. 180 160 Single cross hybrids 1.7 Bu per acre per year (1.8% per year) Bushels per Acre 140 120 100 80 60 40 Open pollinated ‐0.1 Bu per acre per year (‐0.3% per year) Double cross hybrids 1.0 Bu per acre per year (2.8% per year) Biotech hybrids 2.6 Bu per acre per year (1.9% per year) 20 0 Year Source: USDA – NASS rage. US. yield · Corn is C4 Crop high because it's a Reproduction in Plants Occurs via seeds Sexually reproducing plants are either self‐ or cross‐ pollinated or a mix Mode of reproduction of crops determines breeding methods http://carolinas‐tacf.org/albums/2005_Pollinations/0.jpg 2 10/7/2014 Basic Genetics nucleus contains Cell nucleus chromosomes that control inheritance Chromosomes are made of DNA organized into genes genes Chromosomes occur in pairs alleles Genes and alleles http://micro.magnet.fsu.edu/cells/chloroplasts/im ages/chloroplastsfigure1.jpg Mitosis movie http://med.mui.ac.ir/slide/genetic/mitosis4.gif http://www.infovisual.info/01/021_en.html 3 10/7/2014 Basic Genetics (continued) Genotype—total genetic makeup Phenotyp Phenotype—due to genotype, the environment, and their interaction Heritability—proportion of phenotype controlled by genetic factors Qualitative Qualitative traits—discrete, controlled by one (ex flowers) or a few genes Quantitative traits—more complex, controlled by several genes lex Yield).. Mendelian Genetics A A a Aa Aa a Aa Aa A a A AA Aa a Aa aa 4 10/7/2014 Plant Breeding Goals Yield—complex quantitative trait – Selection for disease and insect resistance, competitiveness, and drought tolerance Quality traits—starch fermentation characteristics or forage digestibility Harvestability—specific crop modifications to reduce loss Persistence—enhanced survivability over the long term Plant Breeding Strategies Collect sources of genetic variation Determine parent materials Generate new genetic combinations Selection of desired combination of traits Crossing & hybridization Evaluation trials New variety Distribution to growers 5 10/7/2014 Breeding by Pollination System Self‐pollinated plants – Usually homozygous – Common methods of breeding include pedigree selection or mass selection Breeding by Pollination System Self‐pollinated plants – Usually homozygous – Common methods of breeding include pedigree selection or mass selection Cross‐pollinated plants – Heterozygous – Can use mass selection – Hybridization most commonly used 6 10/7/2014 Genetic Engineering Uses gene transformation to transfer genes of interest – Genes may originate from wide range of sources – Transfer occurs via bacterium or gene gun Used for qualitative traits like herbicide and disease resistance http://www.nwcreation.net/images/genegun2.gif imol.vub.ac.be/subtopic3_plan.html 7 10/7/2014 GMOs – Friends or Foes? Potential benefits: Biological pest resistance – Bt corn Herbicide tolerance – Roundup Ready Adaptation to environmental stresses – salts Desirable functional characteristics – shelf life Desirable nutritional characteristics – golden rice GMOs – Friends or Foes? Potential concerns: Overall safety unsure Long term impact on human health unknown Outcross with weedy relatives Unintended effects on non‐target organisms Pests may develop resistance to technology Ethical and religious issues Traditional Breeding versus Genetic Engineering Traditional Breeding Years to release variety Transfers many genes Uses only genes of same or related species Not prohibited Genetic Engineering Faster release of varieties Transfers few genes of interest Can use genes from any species Prohibited in some countries 8