Rucete ✏ Campbell Biology In a Nutshell
Unit 6 PLANT FORM AND FUNCTION — Concept 38.3 People Modify Crops by Breeding and Genetic Engineering
Humans have shaped plant evolution through artificial selection and now through genetic engineering. From traditional breeding to transgenic crops like Bt maize and Golden Rice, biotechnology is transforming agriculture, raising both promising solutions and ethical/environmental concerns.
Artificial Selection in Agriculture
- Artificial selection: early farmers selected traits like larger seeds, non-shattering grains, and delayed seed dispersal.
- Maize was derived from teosinte by selecting for larger, attached kernels.
- Traditional breeding crosses domestic and wild plants to improve disease resistance and drought tolerance.
- Drawbacks: desirable traits are often linked to undesirable ones (e.g., small fruits), and breeding takes many generations, sometimes requiring embryo rescue.
Genetic Engineering and Biotechnology
- Genetic engineering: allows gene transfer between unrelated species (e.g., daffodil gene into rice).
- Plant biotechnology includes:
- General innovations using plants and plant products.
- Genetically modified organisms (GMOs): created using tools like CRISPR.
- Transgenic plants contain foreign genes (e.g., Bt maize with a bacterial gene to kill pests).
Applications of Genetic Engineering
Increasing Yield and Reducing Inputs
- Bt crops: reduce pesticide use and insect damage.
- Glyphosate-resistant crops: simplify weed control but can lead to herbicide-resistant weeds.
Enhancing Nutrition
- Golden Rice: produces beta-carotene to prevent vitamin A deficiency.
- Biofortified cassava: engineered for increased iron, beta-carotene, and virus resistance.
Boosting Energy Independence
- Biofuels: generated from plants like switchgrass or poplar instead of fossil fuels.
- Genes enhance cellulose conversion efficiency and biomass production.
Agricultural and Ecological Concerns
Human Health
- GMOs may reduce pesticide exposure.
- No proven allergenicity, but genes known to cause allergies must be avoided.
Nontarget Organisms
- Example: Bt maize was falsely linked to harm in monarch butterflies—later disproven.
- Gene targeting and field testing improve safety.
Transgene Escape
- Superweeds may result if GM traits spread to wild relatives.
- Example: glyphosate-resistant turfgrass escaped into wild.
- Solutions:
- Engineer male sterility or apomixis (asexual seed formation).
- Insert genes into chloroplast DNA (maternally inherited).
- Control flower opening to limit pollen spread.
In a Nutshell
Human influence on crops began with artificial selection and now includes advanced genetic engineering. GMOs offer improved yields, nutrition, and sustainability, but also raise concerns about safety and ecological impact. Balancing innovation with responsibility is key to a secure agricultural future.