1. Chapter 14 – Plant Biotechnology

2. What is plant biotechnology?
Manipulating plants and plant parts for practical uses
Improved food crops
Higher yields
Improved nutrition
Environmental tolerances
Improved production of valuable molecules
Production of novel molecules

3. Biotechnology & agriculture
Terminology
Transgenic
GMO
GM crop

4. Biotechnology and modern agriculture

10. A brief history of crop improvement
Strategies to manipulate genomes
Selection of desirable traits (manipulating population genetics)
Introducing new genetic traits to a genome
Hybridization technologies
Cross pollination
Plant tissue culture (protoplast fusion)
Gene transfer technologies
Genetic “transformation” (gene gun, Agrobacterium tumefaciens)
Create a new trait (directed evolution)

11. Crop domestication
Artificial selection since ~9,000 B.C.

12. Origins of crop domestication

15. K.-i. Tanno et al., Science 311, 1886 (2006)
Fig. 1. Modern examples of dehiscent wild einkorn wheat ear (A) and spikelet (B). Detail of spikelet with smooth wild abscission scar (C), indehiscent domestic ear (D), and detail of spikelet with jagged break (E) are shown. The bar chart (F) gives relative frequencies of subfossil finds with the absolute figures.
K.-i. Tanno et al., Science 311, (2006)
Published by AAAS

17. Selection of desirable genetic traits

18. Genetic selection and crop domestication

20. Many selection strategies have been developed
Example: Mass selection

21. Limitations of selection
Restricted to genetic traits existing within the crop species
Homozygosity and inbreeding depression

22. Introducing new traits: Hybridization
Cross-pollination
Domesticated variety as one parent
Related variety or species with a desirable traits

23. Crop improvement, hybridization & gene pools
Closely related species
vs.
Distantly related species
Cladograms depict evolutionary relationships

24. Backcrossing to introgress a desirable trait

25. Hybridization and selection necessary to retain desirable traits

26. Backcrossing X X X Donor parent (DP) (wild/res.-RR)
Recurrent parent (RP)
(domest./sus.-rr) X
F1 hybrid
50% DP; 50% RP
All Rr X
Recurrent parent
(domest./sus.-rr) F2 X
Recurrent parent
(domest./sus.-rr)
25% DP; 75% RP
1-Rr:1-rr
Which genotype should be used for the next cross?

27. Genetics of backcrossing
Generation
Donor genes
Recurrent genes
Parent
100% F1
50%
1st bc
25%
75%
2nd bc
12.5%
87.5%
3rd bc
6.25%
93.75%
4th bc
3.12%
96.88%
5th bc
1.56%
98.44%
6th bc
0.78%
99.22%
7th bc

28. The earliest technique utilized to improve agricultural crops was
Cross pollination
Selection
Back crossing
Hybridization

29. Backcrossing involves
Self pollination
Crossing a crop to be improved repeatedly back to a related wild species containing a desirable trait
Crossing the hybrid offspring of a cross pollination repeatedly back to the domesticated parent
Both 1 and 2
All of these

30. Germplasm conservation
Gene banks are repositories for genetic traits
National Genetics Resources Program
Consultative Group on International Agricultural Research

31. Limitations of hybridization
Restricted to plants that can naturally hybridize
Crosses to closely related species usually successful
Hybridization to distantly related species usually problematic
Little to no seed produced
Hybrids recovered are often sterile
Genetic drag (linkage)

32. Breaching reproductive barriers for crop improvement
Plant tissue culture
Embryo rescue
Protoplast fusion
Micropropagation
Somatic embryos, Sitka spruce

33. Protoplast fusion for hybridization

36. Wide crosses can be accomplished via protoplast fusion and tissue culture regeneration
Brassica juncea (Pbt) x Thlaspi caerulescens (Znt & Nit)

37. Breaching reproductive barriers for crop improvement: Recombinant DNA technology & genetic engineering

38. Recombinant DNA technology and crop improvement
Allows utilization of every species
Allows direct transfer of a single gene
Requires a method of gene transfer into plant cells
Requires regenerable plant cells
Totipotency of many plant cell types allows for regeneration of entire plants from single cells

39. Whole plants can be regenerated via cell and tissue culture

40. Somatic embryogenesis
callus

41. Plant transformation technologies
Genetic transformation – creating transgenic organisms
Agrobacterium
Gene gun
Gene transfer to protoplasts

42. Agrobacterium transformation

43. T-DNA of A.t. becomes integrated in a plant chromosome

44. T-DNA can be customized

46. Limitations of Agrobacterium transformation
Does not infect (most) monocots
Different A.t. strains have different levels of virulence in different plant species

49. Gene Gun (animation)
Invented by Cornell researcher, John Sanford

52. Electroporation of protoplasts

53. Polyethylene glycol mediated transformation of sugarbeet stomatal guard cell protoplasts
Why guard cell protoplasts?
Only totipotent cell type

55. Microinjection of protoplasts

57. Examples of crop improvement through genetic engineering
Engineered herbicide resistance
Glyphosate (RoundUp™) and EPSP synthase

58. Shikimate pathway X EPSP Glyphosate
(3-Phospho-5-enoylpyruvylshikimate)