Beckles - Biotechnology Postharvest Qualityucce.ucdavis.edu/files/datastore/234-1601.pdfGenetic re-arrangement in selective cross breeding vs GE 1. What’s for dinner – Genetic

Biotechnology and Postharvest Quality

Diane M BecklesDepartment of Plant SciencesUniversity of California-Davis

[email protected]://www.plantsciences.ucdavis.edu/beckles/beckles_index.html

Biotechnology

A set of tools (molecular) used to modify the genetic makeup of an organism so that: It produces a new product The product perform new function(s)

Postharvest Quality The factors that ensure maximum income for

producers as well as meeting the nutritional and aesthetic needs of the consumer after horticultural crops are harvested. Producers and consumers often have opposing wants

Consumers

Texture

Flavour

Aroma

Sweetness

Acidity

Color

Appearance

Nutrition Producers

Shelf-life

Chilling-tolerance

MicrobialcontaminationBrowning

Firmness

Diseaseresistance

Genotype

The genetic composition of an organism. Contains all of the information that

determines final characteristics.

Postharvest traits are due to the interaction of the environment and genotype

Identical genotype Different environment

Different genotype Same environment

Normal tomato

rin: ripeningmutant

25°C

Ripened fruit

Chilling injury

25°C

5°CNormal tomato

Biotechnology can be used to change the gene composition and create genetically engineered organisms (GEOs) with enhanced traits -including those with improved postharvest qualities.

Power of biotechnology

Desirable traits for improving Postharvest Quality of produce

Improved flavour, texture, colour Long storage Delayed ripening Enhanced nutrition and health benefits Better food processing Nutraceuticals

MYTH: Genetic modification of crop plants is new

False: All crop plants have been genetically modified

Biotechnology is another (more sophisticated) tool used to genetically modify crop plants

DomesticationScience-based Selective breeding

Mutagenesis breedingEmbryo culture

Biotechnology and geneticengineering

Sophistication of technology

Genetic modification of crop plants

1. Domestication. 2. Selective breeding. 3. Mutagenesis breeding. 4. Embryo culture. 5. Biotechnology.

Domestication: cultivated vs wild tomato

Wild Modern cultivated tomato tomato

From Frary et al., 2000 Science

Wild banana vs modern cultivars

Wild banana with seeds Cultivated banana- sterile


1. Domestication 2. Selective breeding 3. Mutagenesis breeding 4. Embryo culture 5. Biotechnology

2. Selective breedingSolanum

lycopersicon

Solanumperuvianum

Wild species has resistance to nematodes

Percent of “wild” genes 50%

25%

12.5%

Using the wild tomato species as a source of genes for nematode resistance

Six or more generations of backcrosses to the cultivated parent, selecting for resistance at each generation

6.25%

3.125%

1.5%

0.75%Kent Bradford, Depart Plant Sciences, UC Davis

Selective breeding

Cauliflower and broccoli were derived from the same genetic ancestorBrassica oleracea

California Agriculture vol 58 #2; http://CaliforniaAgriculture.ucop.edu

Genetic diversity

From : “What is Biotechnology?” by Dr. Peggy Lemeaux; University of California, Berkeley



3. Mutational breeding

Radiation breeding: Texas red grapefruit variety Rio RedDeveloped by mutation of Ruby Red. There are more than 2000Crops which were produced by radiation

Chrispeels and Sadava, 2002 Plant, Genes and Crop Biotechnology; ASPB



4. Embryo rescue-laboratory culture of plant embryos

Inter-species crossing Embryo cannot naturally develop into a mature plant Embryo must be dissected and nurtured on media

Fruits cultivated by embryo rescue

Early-ripening stone fruit varieties

All seedless grape varieties

Small immature embryos that must be cultured individually in test tubes to grow a hybrid seedling.



5. Biotechnology

Manipulations done at molecular level. Specific genes may be changed. Gene function usually understood. Genes can be transferred between species.

Tenets

All living organisms characteristics determined by DNA.

DNA code broken – functions known for most DNA sequences.

DNA is fundamentally the same in all organisms DNA should be interchangeable between species.

Gene identification

Genes encoding important traits Extended shelf-life Insect, disease resistance Uniform ripening Increased sugars Enhanced Aroma Antioxidants

Gene manipulation

Gene expression in crop is altered in various ways Suppression (a deleterious gene) Over-expression (favourable gene) Modification (enhancing a characteristic) Transgene expression (introducing new function)

How genetic engineering of plants works

A gene of known function in plant is identified (e.g. gene controlling fruit ripening) and isolated.

The gene must be stably incorporated into plant.

The gene must be heritable.

Genes are introduced into the plant using bacterial plasmid as vectors

Gene to be suppressed or overexpressed

Plasmids are circular molecules of DNA found in bacterial cells. They confer survival to antibiotics

How to get the DNA into the plant

Agrobacterium tumesfaciens (more precise).

Particle bombardment (random insertion of genes).

Regeneration from single cell to whole plant

drawing by Celeste Rusconi, © Regents of the Univ. California

Biotechnology & Postharvest biology Can we use these tools to improve the postharvest

quality of horticultural crops?

Adel Kader, Dept Plant Sciences, UC Davis

Yes…..maybe

Transgenic papaya resistant to papaya ringspot virus


Non-transgenic Transgenic

Transgenic plums resistant to plum pox virus

Non-transgenic fruit Transgenic fruit


Novel ornamentals

Florigene Moonshadowtransgenic carnations; produces intense blue-violet colour.

Flavr Savr tomatoes – extended shelf-life

Chrispeels & Sadava, 2002 Plant, Genes and Crop Biotechnology; ASPB

Uniform/delayed ripening

Transgenic tomatoes with altered ethylene production.

Harvest can be done every 2 days instead of twice a day.

Fruit stays in field longer without deteriorating.

Non-transgenic Transgenic fruit4-colours 2-colours

From : “What is Biotechnology?” by Dr. Peggy Lemeaux; University of California, Berkeley

Delayed softening/ripening in transgenic apples

Dandekar et al (2004) Transgenic Research 13 373-384

Transgenic

Transgenic

Transgenic

Control

What’s the problem with GE?

Polarizing and disparate views of the technology

GE crops – harmful to living creatures?

© Drawing by Nicholas Eattock, Dept Plant Sciences UC Davis

GE crops will create monsters


GE crops – a cure-all


GE crops - bountiful harvests


Public perception of GE

FACTOR Coerced vs. voluntary

Industrial vs. natural

Dreaded vs. not dreaded

Unknowable vs. knowable

Untrustworthy rather than trustworthy

Unresponsive vs. responsive management

EXAMPLE Everyone must eat GE food if

unlabeled. Big multinational hybrid vs. landraces.

Unknown risks (cancer?)

Only experts know the risk, and they debate

Multinational vs. small farmer

Open vs. arrogant and remote

Chrispeels and Sadava, 2002 Plant, Genes and Crop Biotechnology; ASPB

Getting to the truth about GE crops

Facts vs fiction about GE crops

Myth GE plants will create superweeds.

FactGE plants will create weeds just like most crop plants; cannot determine the impact on the environment.


MYTH GE foods have genes and normal food do not.

FACT All living organisms have genes.


MYTH Almost all crops are GE.

FACT The cost of meeting regulatory requirements ($20-30 million per crop)

limits the number of GE crops commercialized. This

is especially true of horticultural crops (only 2-3 exist).


MYTH There will be animal genes in fruit and vegetables.

FACT Technically possible to accomplish this ……..but no company would commercialize

a product which would be reviled by the consumer – bad business!


MYTH GE food are unnatural.

FACT So are all of the foods (including fruit and vegetables we eat

today!).


MYTH When you transform plants you do not know what is happening.

FACT With transgenics you introduce a single gene, with traditional

breeding you may introduce hundreds of unknown genes.

Genetic re-arrangement in selective cross breeding vs GE

1. What’s for dinner – Genetic engineering from the lab to your plate.”2. Gepts, P. (2002) Crop Science 42:1780-1790


MYTH Farmers in developing countries will not benefit.

FACT Governments of many developing countries have adopted technology

pioneered by multinationals.

http://www.fao.org/biotech/inventory_admin/dep/default.asp


MYTH GE food will contain allergens and toxins

FACT (i) We consume 10,000 toxins daily. Coffee contains 1000 toxins, of

27 tested 19 were carcinogens.

(ii) Peanuts, brazil nuts, wheat cause serious allergic reactions


MYTH Transgenes will move from plants to humans once ingested

FACT No-one has shown that genes move from ingested food into

human cells


MYTH GE crops are not adequately tested or regulated

FACT There are greater testing requirements for GE crops compared to traditional crops

http://usbiotechreg.nbii.gov/lawsregsguidance.asp

Substantial Equivalence

Numerous scientific reviews have concluded that food created by genetic engineering presents no greater dangers than genetic changes introduced by other methods.

The product should be evaluated, not the method by which it is produced.

Bradford et al., (2005) Nature Biotechnology 23: 439-444

Limits to application of biotechnology to Horticultural crops

Economies of scale. Expensive to apply to niche crops and cultivars

Technologies not sufficiently developed for individual crops. Long generation times - not tractable.

For tree crops – use grafting!Transgenic walnut shoot grafted ontocontrol rootstock in B while crowngalldevelops in non-transgenic shoot graftA

Escobar et al (2001) Proc Natl Acad Sci USA. 98:42

Limits to application of biotechnology to Horticultural crops

Several postharvest traits are complex Multigenic; strongly affected by the environment

Public resistance to the idea. More intimate ‘association’ with fruit and

vegetables than maize or soybean products

Gene transfer to non-GE crops. Disturbing evidence that native landraces in Mexico

pollinated by GE crops*

Positional Effects. Disruption of native genes at the site where the construct

is inserted**

Monopolization/Concentration power by seed companies

They determine the traits worthy of investment. Humanitarian interests may not be prioritized.

Unresolved Issues

*http://www.plantsciences.ucdavis.edu/gepts/mec_3993_LOW.pdf**Gepts, P. (2002) Crop Science 42:1780-1790

Real risks of common activities from actuary data

Number of deaths divided by number of people engaged in the activity fromChrispeels & Sadava, 2002 Plant, Genes and Crop Biotechnology; ASPB

Summary

Biotechnology holds great potential for improving postharvest biology of horticultural crops

No technology is risk-free or is absolutely safe Genetic modification of crops is not new Today we have better, more sophisticated tools to

achieve crop improvement Scientists must adequately address food and

environmental risks as well as public concerns about the technology

Bibliography/Sources

Chrispeels and Sadava, 2002 Plant, Genes and Crop Biotechnology; ASPB Bradford KJ & Alston, J. (2004) California Agriculture vol 58(2):84-85

http://CaliforniaAgriculture.ucop.edu Bradford et al (2004) California Agriculture 58(2):68-71 http://CaliforniaAgriculture.ucop.edu Clark et al (2004) California Agriculture 58(2): 89-98 http://CaliforniaAgriculture.ucop.edu Lemaux, P. (1998) What is biotechnology?

http://ucbiotech.org/resources/biotech/slides/biotech.html retrieved 5/20/03 “What’s for dinner – Genetic engineering from the lab to your plate.”

http://www.foodsafetynetwork.ca/biotechres/newpdfs/pg9-18.pdf retrieved 5/20/03

Prakash C.S. : Agricultural Biotechnology and Food Security”www.agbioworld.org retrieved 5/20/03

Bibliography/Sources (cont’d)

Bradford et al., (2005) Nature Biotechnology 23: 439-444 Dandekar et al (2004) Transgenic Research 13: 373-384. Frary et al. (2000) Science 289. no. 5476, pp. 85-88 “Introduction to Genetic Analysis” Anthony Griffiths 9th Ed (2008). W.H.Freeman

Publishers Gepts, P. (2002) Crop Science 42:1780-1790 US Regulatory Agencies Unified Biotechnology website http://usbiotechreg.nbii.gov/lawsregsguidance.asp Cartoons by Nicholas J. Eattock, Dept Plant Sciences, UC Davis

Documents

Beckles - Biotechnology Postharvest Qualityucce.ucdavis.edu/files/datastore/234-1601.pdfGenetic re-arrangement in selective cross breeding vs GE 1. What’s for dinner – Genetic