Transcript No Slide Title

AGR2451 Lecture 16: “The Past and Future of Agriculture”
•Mid-term Exam – 1-2:20pm Tues, November 12th
Last name: A-K – Room Richards 124
Last name: N-Z Room Richards 022
•No reading this week.
•Review of the last lecture:
1. What is a plant? (Review)
These last 16 lectures have been about trying to build a plant as
evolution did from the Primordial Soup.
So, 3 billion years later, what is a plant and why is it useful for animals
and humans (agriculture)?
•Life is a series of biochemical reactions that gather or metabolize
nutrients (C, N, O, P, S, etc.) into macromolecules.
•Life organizes biochemistry by switching on/off genes that encode
enzymes or structural proteins to create organelles, cell types, organs,
or environmental responses.
•Whereas animals are mobile and heterotrophic, fungi are immobile and
heterotrophic, plants are immobile and autotrophic.
What are the implications of this strategy? (for you to think about)
•A plant body is nothing but a nutrient-gathering machine:
From Plants, Genes and Agriculture, page 460
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
Slide 16.1
1. What is a plant (continued)
•A plant gathers nutrients to build complex molecules to build organized
structures.
Why? to propagate its own DNA
How? as it senesces (annuals) or perennials, it transfers nutrients from its
vegetative structures to ensure the survival of its progeny DNA.
•Flowering plants developed seeds and fruits.
•Thus, the plant vegetative body is both a nutrient-gathering machine
and a nutrient-storage machine connected to its reproductive structures.
•Because a plant is immobile, it substitutes shunting of primary
metabolism (abiotic stress) and production of secondary metabolites
(biotic interactions) for animal behaviour.
•Secondary metabolites allow a plant to communicate with its
environment (signals to attract Nitrogen-reducing bacteria, pollinators..).
•Because a plant is a rich source of nutrients and immobile, it must invest
a lot of its resources to fighting pathogens.
Slide 16.2
2. How did the last 10,000 years and the Green Revolution improve
plants for human use? (Review)
•selection against secondary metabolites (pesticides) in grains (seeds) and
other storage tissues; if used for silage, then selection against pesticides
in leaves. Implications?
•effect on flowering photoperiod?
•early maturation = shorter growing season (related to flowering)
change in C/N allocation. How?
•selection against seed shattering (against natural seed dispersal)
•pest and disease resistance; abiotic stress resistance
•delayed senescence of photosynthesis during grain-fill or fruit-fill
period
•selection against indeterminate growth. What is it and why?
•selection against seed dormancy requirements
•selection against allelopathy – this may have contributed to our
enhanced need for herbicides (?)
•selection for enhanced nutrient quantity and quality (starch, protein,
oils) and vitamins in storage organs
•semidwarf varieties – why?
•farming practices towards monocultures, irrrgation, NPK fertilizers,
pesticides, herbicides; loss of genetic diversity; use of machinery,
decline in labour, use of larger farms; change from more sustainable
farming practices.
•sudden change caused the displacement of farmers, women and
traditional knowledge
Slide 16.3
2. The Last 10,000 Years of Agriculture (continued)
•much higher food production without increased land use;
•the prevention of mass starvation.
What has caused the surge in human population in the last 60 years?
From Plants, Genes and Agriculture, page 15
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
•in the last 30 years, the yields have doubled
From Plants, Genes and Agriculture, page 307
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
Slide 16.4
3. What must the next Green Revolution do?
3A. GOALS
1. •••We must produce more food in the next 50 years than in the entire
history of humanity. Why?
a)
b)
2. Biggest concerns?
a)Freshwater
b)Global warming
From Plants, Genes and Agriculture, page 40
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
c)Marginal lands
From Plants, Genes and Agriculture, page 440
M. Chrispeels and D. Sadava (1994)
3.Need for Sustainability
Jones and Bartlett Publishers, Boston, MA
-food production
-basis of renewable-resource manufacturing, polymers, medicines, etc.
4. Need Enhanced profits for farmers.
Slide 16.5
3B. HOW? What are the CURRENT LIMITATIONS for plants
as a nutrient-gathering machine for humans?
Premise: Agricultural plants are nutrient gathering and storage machines.
As they senesce, they transfer nutrients to their reproductive structures.
a)Rubisco. What are the 2 problems?
Consequences?
Solution?
b)Nitrogenase – What is the problem?
What is the solution?
c)Rhizosphere – Plants give up to 30% of their fixed carbon to the
Rhizosphere. Why?
d)Plants senesce (stop photosynthesis) as grain-fill begins. How can
this be overcome?
e)Ratio of C/N allocation to vegetative structures vs. harvest tissues.
f)Inability to use saltwater as a consequence of plant evolution onto land.
g)Cellulose cell walls. This prevents humans from directly eating leaves.
h)Abiotic stress tolerance – drought, cold, heat, salt – to overcome yearly
variations. How?
i)Biotic stress tolerance and develop a way to prevent resistance
j)Hybrid vigor – Determine what causes it and how to sustain it beyond
the F1 generation.
k)Using other crops. Creating new crops (hybrids) by breaking species
barriers – this has been the basis of land plant evolution. How?
L)We need a better understanding of the biology of crops that store their
carbon as underground storage tubers (cassava, sweet potatoes, yams).
Slide 16.6
3. Limitations to Agriculture (continued)
•We need to overcome these limitations and combine them with
sustainable farming practices.
•Sustainable farming preserves the environment without an ideology of
how to do this – nothing is necessarily excluded (unlike in “Organic
Agriculture”):
I)crop rotations – implications for pests/disese and Nitrogen
II)green manures – plow forage legumes (alfalfa, clover,etc.) into soil
III)conservation tillage/no tillage – mechanisms to preserve ground cover
to prevent soil evaporation and prevent soil erosion
IV)Integrated Pest Management – use natural enemies of pests, resistant
plants and good crop management, use pesticidse at most effective times
V)genetic diversity – multiple genotypes of one species or multiple
species = resistance against disease/pests; roots that extend to different
heights to make better use of soil nutrients and moisture.
Caviats
All of the above is in the world of Biology; in the real world, there are
many more pressing issues for agriculture like poor infrastructure, trade
policies, access to technology, access to loans to buy technology,
government subsidies and unfair trade practices; poor education for
women, corrupt governments and war.
Slide 16.7
4. Curent and Future Techniques for Crop Gene Improvement
a)Breeding
•Breeders select for the final phenotype by selecting for multiple
mutations at multiple genes at once
•Breeders select for subtle mutations, whereas geneticists/molecular
biologists select for extreme mutants
•Breeding is slow.
From Plants, Genes and Agriculture, page 340
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
• during the last 20 years, the time required to introgress and select for the
trait of interest has been decreased by >50% by marker-assisted selection.
What is the principle behind this and how does it work? On board
Slide 16.8
b)Molecular Biology & the use of Transgenes:
•selection for genes, then determine the phenotype
•the key advantage is that transgenes can break the species barrier
Examples? “Golden rice” - high iron and vitamin A (beta-carotene) into
rice endosperm using transgenes
-120 million children are VitA deficient
-1-2 million deaths
-Golden Rice = 10% of daily requirements (so far)
From Plants, Genes and Agriculture, page 106
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
Vitamin A = carotenoid derived from isoprene metabolism
Ye et al. (2000) Engineering the ProvitaminA (betacarotene) biosynthetic pathway into (carotenoid free) rice
endosperm. Science 287, 303-306.
AAAS Publishing, Washington, D.C.
Slide 16.9
Other traits in progress by molecular engineering
*naturally decaffeinated coffee!!
From Plants, Genes and Agriculture, page 406
M. Chrispeels and D. Sadava (1994)
Jones and Bartlett Publishers, Boston, MA
c) Emerging techniques:
Chimeroplasty?
Medicines for plants?
Bioinformatics?
”Gene chips and protein chips”
Slide 16.10
.What will Agriculture look like in 20-30 years??
•enhanced C/N/H20-use efficiencies for food production
•enhanced abiotic and biotic stress tolerance
•plants as fuel cells
•plants as the basis of carbon-based fuels (ethanol)
•plants for industrial use polymers– DuPont creating nylon fibres from
corn
•phytoremediation - using plants to clean up environmental toxins
•plants as factories of vaccines, vitamins and nutrients for human health
(“nutraceuticals”)
THE SKY IS THE LIMIT!!!
.Final Comments
•perhaps only 1% is known about the biology of plants!!
•knowledge is the power to change and make a practical difference, not
ignorant protest
•plant research is a race against time (30-50 years)