COURSE OBJECTIVES

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ABIOTIC PLANT STRESS
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PLANT STRESS

1. Any external factors that negatively influence
   plant growth, productivity, reproductive capacity
   or survival
2. Any change in environmental conditions that
   produce a less than ideal plant response
3. Any change in environmental conditions that Have
   a potentially adverse effect on a plants
   survival, growth, and reproduction
4. Any change in environmental conditions that have
   a devastating impact on crop yields in
   agriculture

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Abiotic Stresses
Environmental, non-biological Stress Water
(high/low) Oxygen Nutrients Temperature
(high/low) Salt Radiation Pollutants Excess or
deficit
http//www.geo.arizona.edu/gallery/US/tuc_2.html
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WATER STRESS

• Drought leading to water stress is a major
  problem in reducing agricultural productivity
  especially in tropical, semi-arid and arid
  regions of the world
• Water deficits result from low and erratic
  rainfall, pooor soil water storage and when the
  rate of water transpiration exceeds water uptake
• The cellular water deficits resulr in the
  concentration of solutes, loss of turgor, change
  in cell volume, disruption of water potential
  gradients, change in membrane integraty,
  denaturation of proteins and several
  physiological and molecular components
• The stress effects depend on the degree and
  duration of stress, developmental stage of plant,
  genotypic capacity of species and environmental
  interaction

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FLOODING STRESS

• Soil water logging and submergence (collectively
  termed flooding) influence species composition
  and productivity in numerous plant communities
  world wide
• Hydrological patterns can determine the
  vegetation in natural and man-made wetlands,
  since this is dependent on ecophysiological
  responses of species to flooding
• In Rice farming, flooding regimes are manipulated
  or are accommodated by genotypes selection to
  secure much of the world production of this
  staple crop
• For most crops, excess water is a major
  constraint to productivity , adversely affecting
  grain yields
• A major constraint from excess water, at least
  for poorly adapted species is an inadequate
  supply of oxygen to submerged tisuue

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SALT STRESS

• Salinity affects agricultural production and its
  quality in arid and semiarid regions, where
  rainfall is limited and is not sufficient to
  transport salts from the plant root zone
• Salinity arises due to increase in the
  concentration of salts like sodium chloride,
  sodium carbonate, sodium sulphate or salts of
  magnesium. The dominant salts are either sodium
  chloride or sodium sulphate or mixtures of them.
• The effect of salinity of plant is complex and
  its adverse effects include ion toxicity, water
  deficits and nutrient imbalance and deficiencies

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SALT STRESS

• The saline soil management includes crop
  selection, crop stand establishment, leaching
  requirement, drainage and other reclamation
  practices
• Salt tolerance mechanisms are highly complex
  since the effect are diverse and are controlled
  by a number of genes or group of genes
• Salt tolerance is generally associated with
  regulated ion uptake compartmentation of ion and
  gene product including stress proteins
• Ion homeostasis is important component of salt
  tolerance

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HIGH TEMPERATURE STRESS

• The global mean temperature increased by 0.6 C
  between 1990 to 2000 and is projected to
  increase by another 1.4 to over 5 C by 2100
• Plants suffer the ups and downs of temperature of
  their environment and estimate decrease in crop
  yield range up to a 17 for each degree Celcius
  increase
• The effect of temperature to plants is strongly
  dependent on ambient air temperature and radiant
  energy fluxes
• All organisms when exposed to rapid increase in
  external temperature generally 5 to 10 C above
  normal temperature for a period of few minutes to
  a few hours exhibit synthesis of an elite set of
  protein called heat shock proteins (HSP)
• HSP proteins are involved in cellular repair,
  rescue, clean up and/or protection during stress
  and from its recovery

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PHOTOOXIDATIVE STRESS

• Light stress is one of the important
  environmental constraint that limit the
  efficiency of photosynthesis and plant
  productivity
• Plant when absorbed light energy exceeds the
  capacity for light energy utilization in plant
  photosynthesis, the photosynthetic efficiency
  will be reduced due to the formation of AOS which
  can damage photosynthetic apparratus and
  chloroplast components
• Plants are believed to develop certain strategies
  of tolerance mechanisms

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NUTRIENT STRESS

• Plant growth and development and yield are
  contributed by 17 essential elements
• Nutrient stress and associated metabolic
  disorders decrease plant growth and yield
• Plant growth and metabolism is also affected by
  heavy metal stress
• Developing nutrient stress tolerance may help to
  extend agriculture to unexplored harsh and
  nutrient poor soil

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Nutrient Deficiency

• A lack of one or more essential elements needed
  by plants for optimum growth lead to plant
  stress.

Macroelements Macroelements Microelements Microelements
Element Symbol Element Symbol
Nitrogen N Chlorine Cl
Phosphorous P Iron Fe
Potassium K Boron B
Manganese Mn
Calcium Ca Zinc Zn
Magnesium Mg Copper Cu
Sulfur S Molybdenum Mb
Nickel Ni
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HEAVY METAL STRESS

• Supra optimal concentration of heavy metals such
  as Cd, Pb, Hg, Cu, Zn and Ni affect growth,
  development and yield of plants, though Cu, ZN,
  and Ni are essential micronutrients at low
  concentration
• Heavy metals affect several physiological and
  metabolic processes
• Plants have developed several mechanisms that
  control and responds to the uptake and
  accumulation of both essential and non essential
  heavy metals

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HEAVY METAL STRESS

• Tolerance mechanisms vary from species to species
  and their genetic background
• The important heavy metal tolerance mechanism
  include metal binding to wall, reduced transport
  across cell membrane, active efflux of metals,
  compartementation , chelation and sequestration
  of heavy metal by particular ligands such as
  phytochelatins and metallothioneins

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Stress is the driving force behind the process of
adaptation and evolution
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Plant Stress Response
Preferable!

• Stresses cause responses in metabolism and
  development
• Injuries occur in susceptible plants, can lead to
  impeding flowering, death

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Plant Stress Responses
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High temperature Stress
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Phosphorus deficiency
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SULFUR DEFICIENCY
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NITROGEN DEFICIENCY
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STRATEGY TO COPE WITH ABIOTIC STRESS

• Agronomy by managing or manipulating the
  environment
• Plant Breeding using tolerant cultivar

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Importance of Plant breeding?

• Increases in yield are derived both from improved
  varieties and from improved management.
• It suggests about a 50-50 of crop yield split
  between genetic gain and gain attributed to
  management.
• Planting material is the most important input in
  agriculture
• An improved cultivar is the most economic and
  least laborious input for crop cultivation

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General Breeding Procedure
I. Producing initial variation (crossing of
diverse material) II. Development, testing, and
selection of potential cultivar III. Testing
experimental varieties and selection and
multiplication of the best
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Selection breeding methods
In vitro breeding methods
Plant Breeding in the 21th Century
Molecular breeding methods
Transgenic breeding methods
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Outline

1. Abiotic Stress
2. Agronomic aspect of Abiotic stress
3. Physiologocal aspect of Abiotic Stress
4. Molecular Biological aspect of Abiotic Stress
5. Conventional Breeding
6. In vitro breeding
7. . Transgenic breeding
8. Molecular Breeding