Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding and Propagation Chapter 14 Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Outline Crop Plant Evolution Plant Breeding  Sexually Compatible Germplasm  Sexually Incompatible Germplasm - Bacterial Gene Cloning  Transgenic Plants  Seed Propagation  Asexual Plant Propagation

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Crop Plant Evolution Approximately 200,000 species of flowering plants.  Six species provide 80% of calories consumed by humans worldwide. - Wheat, Rice, Corn, Potato, Sweet Potato, and Cassava.  Eight additional plants complete the list of major crops grown for human consumption. - Sugar Cane, Sugar Beet, Bean, Soybean, Barley, Sorghum, Coconut, and Banana.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Origins of Agriculture First plants were domesticated in the Near East around 10,000 years ago.  Root crops and legumes were domesticated 2,000-3,000 years ago. - Plants for forage, decoration, and drugs were first domesticated about 2,000 years ago.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Regions of Domestication

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding Plant breeding is accelerated evolution guided by humans rather than nature.  Breeders replace natural selection with human selection to modify plant genetics. - Primary goal of plant-breeding programs is commonly improved yield.  Disease resistance, pest resistance, and stress tolerance contribute to yield.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding Strategies  Self-Pollination - Plants are capable of fertilizing themselves. - Tend to be highly homologous.  Significant inbreeding  Wheat, Rice, Peas, Tomatoes - Pure-Line Selection - Collecting seeds from several plants, growing seeds from an individual plant in a row, and then selecting the most desirable row.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding  Cross-Pollination - Plants must be fertilized from other individuals. - Tend to be highly heterozygous.  Corn, Rye, Alfalfa and most Fruit. - Mass Selection - Many plants from a population are selected, and seeds from these plants are then used to create the next generation.  Seeds from the best are used to create the next generation.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding Using Sexually Compatible Germplasm Outcrossing in cross-pollinated crops often results in hybrid vigor (heterosis). Cross-pollinated plants tend to exhibit inbreeding depression.  Modern breeders cross pollinate to delete deleterious alleles. - Heirloom Varieties are grown as open- pollinated populations.  Genetic variability allows crop production under different environmental conditions.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Germplasm Collection and Gene Banks A plant’s germplasm is the sum total of its genes.  Current agricultural varieties are often genetically uniform, and thus may not be good sources of genetic variability.  Gene Banks have been established to meet current and future demands of plant genetic diversity. - Seeds or other propagules are put into long-term storage.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding Using Sexually Incompatible Germplasm Protoplast Fusion  Cells of each species are grown in a liquid nutrient solution. - Cell walls are chemically stripped to produce protoplasts.  Protoplasts of two species are mixed together and stimulated with the aid of an electric current or chemical solution, to fuse with each other.  Few successes

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Plant Breeding Using Sexually Incompatible Germplasm Gene Splicing and Transgenic Plants  Transgenic Plants are produced by inserting genes from one plant into another. - Recombinant DNA  Restriction Enzymes cut DNA into fragments with sticky ends.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Plant Breeding Using Sexually Incompatible Germplasm Plasmids are commonly used as cloning vectors.  Small circular bacterial DNA. After cloning, the gene is inserted into plant cells via transformation.  Agrobacterium tumefaciens  Particle Guns

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Gene Cloning

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Bacterial Gene Cloning

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Making A Transgenic Plant

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Transgenic Plants Pros  Transgenic crops are often environmentally friendly. - Farmers can use fewer pesticides. Cons  Effect on non-target organisms, such as insects, in the food web.  Movement of herbicide resistance to weeds.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Seed Propagation Hybrid varieties are often grown from seed produced by crosses between two inbred parents.  Inbred line varieties are typically grown from seed and allowed to self-pollinate. Mature seeds are harvested and stored in a controlled environment.  Viability is best when seeds are maintained in cool, dry storage.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Seed Propagation In preparation for planting, seeds may be dusted with a protectant, such as a fungicide. Seeds must be planted in a suitable bed.  Moist soil to allow seeds to imbibe water. - Dry enough to maintain suitable oxygen levels.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Asexual Plant Propagation Cuttings  Produce adventitious roots. - Cells near the wound must dedifferentiate and create a new meristematic region. Layering  Tip Layering - Bend tips until they touch the ground, and then cover them with soil.  Air Layering - Wounding or Girdling to produce roots.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Cuttings and Air Layering Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Asexual Plant Propagation Grafting  Segments of different plants are connected and induced to grow together as one plant. - Scion - Top section of a graft. - Rootstock - Bottom section of a graft.  Successful grafting depends on good contact between the vascular cambium of the scion and that of the rootstock.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Asexual Plant Propagation Micropropagation  Grow and maintain plants in a disease-free status in test tubes. - Grown in-vitro in sterile medium. - Relies on totipotency of plant cells.  Capacity of a cell to give rise to any structure of a mature organism.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Asexual Plant Propagation Micropropagation usually begins with the establishment of an explant in tissue culture.  Plant parts are disinfested.  Induced to develop multiple shoots.  Microshoots separated and placed in a new medium by subculturing.  Root Formation  Transfer plants back to outdoor environment.

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Review Crop Plant Evolution Plant Breeding  Sexually Compatible Germplasm  Sexually Incompatible Germplasm - Bacterial Gene Cloning  Transgenic Plants  Seed Propagation  Asexual Plant Propagation

Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display