سيمينار المعهد
TRANSCRIPT
Agricultural Research Central Plant Pathology Research Institute
Wheat Disease Department
Classical and molecular approaches in wheat breeding to rust diseases
By Dr. Mohamed Abdelkader
Introduction• Wheat is the most widely grown and consumed
food crop in the world with a current annual production level of more than 651 million tones on a total production area of 217 million hectares.
• By the year 2050, the world population is estimated to be 9 billion and the demand for wheat will exceed 900 million tones (FAO 2012).
• Fulfilling this demand is very challenging in the face of climate change, increasing drought, heat stress, and emergence of new virulent diseases and pests.
Breeding progressBreeding better cultivars has become a highly efficient way to improve plant production for yield, quality and reduced input
Classical variety breeding
Determination of the ideotype, breeding objective
Assesment of genetic variation, genetic resources
Crossing + Evaluation + Selection
Screening, data management
Release of new variety
Maintenance breeding – stability of traits
Photoperiod insensitivity cultivars
Shuttle breeding program at two contrasting locations in Mexico, wide adaptation Semi dwarf cultivars
Norman Borlaug
Borlaug was a plant pathologist/breeder work
in developing new varieties of wheat starting in the 1940s spawned the “Green Revolution,” and is
credited with saving at least a billion lives.
Wheat Breeding Objectives
• High yield potential and broad adaptation
• Resistance to major diseases and insects
• Drought, heat, cold and salinity tolerance
• Grain quality
Pre breeding Program • Commonly known as Genetic Enhancement or Germplasme
Development• Pre-breeding is the most promising alternative to link genetic
resources and breeding programs. • Pre-breeding refers to all activities designed to identify desirable
characteristics and/or genes from un adapted (exotic or semi-exotic) materials, including those that, although adapted have been subjected to any kind of selection for improvement.
1. Multi test locations even inside or outside the country at rust hot spot
2. Estimate yield components and grain quality
Genotype by environment interaction
Identification of wheat rust resistance genes
Should be done at pre breeding
program
Promising lines
Identification of wheat rust resistance genes
• 1- Gene postulation( probable) • 2- Genetic analysis• 3- Using DNA markers
Advantages:-
1- Analysis can be done in several weeks
2- Easy when only a few genes are present .
Gene postulation
Disadvantages:-
1- A collection of races differing in virulence is required.
2- The presence of a gene is indicated but not proven.
3- This method used only in identification of resistance
genes that express in seedling plants and not
appropriate for the identification of resistance genes that are
expressed in adult plants.
4-When more than one effective resistance gene is present in a
cultivar or breeding line, the characteristic infection types of the
individual genes are often altered due to interaction between the
resistance genes.
2- Genetic analysisAdvantages:-
1- Very accurate.2-This method used for identification resistance
genes that express in seedling plants and also appropriate for the identification of resistance genes that are expressed in adult plants.
Disadvantages:-1- This method needs at least 3 years for
identification any resistance genes .
Advantages:• Detects variations directly at DNA level• Not influenced by environment• Numerous in number• Automation is possible
Disadvantages:-• Costs • Trained peoples
Molecular techniques
Sources of variation • Introductions: either as varieties or agermplasm
• Selection: Mass selection or individual plant selection
Hybridization: Genetic recombination through intra- and
inter- specific crosses
•Mutations
Efficient breeding program depends on Definition of clear and priority objectives
Cultivarresistance
Monogenic resistance
Polygenic resistance
Fast lastDurable
One specific race More than one race
Resistance can be:
Quantitative, incomplete, (many genes with small effects)
Qualitative, complete Gene-for-Gene interaction
• Understanding of genetics of traits.
• Availability of genetic variability and of parental
material.
• Selection effectiveness including team work, quality
testing, agronomic and molecular techniques.
• Breeding methodologies and population
characteristics.
• Adequate funding and respect of breeders property
rights.
We need to know about the pathogen population structure and the available resistance sources in order to design a resistance breeding program.
Collection of isolates
Phenotyping on host differential sets
Race structure of pathogen
Sources of resistance from host
Selection of Parents
“Mega-Varieties” with wide adaptation ICARDA/CIMMYT lines with high yield
potential, disease resistance, and
grain quality Regional or global performance in
International Nurseries Disease reaction globally or in “hot spots” Physiological characterization DNA Marker data (specific primers)
Hybridization
1- Parents should be planted as single plant as possible 2- Parents should be planted in three successive sowing dates at 15 days 3- Suitable spike must be taken
Types of crossesSingle /Simple Cross
.
Single /Simple Cross
Bulk method Pedigree method
• F2 plants planted individually
• Each selected plant have a number
• pure line
From f2 plants to f6 plants all of them
planted as bulk
Pedigree selection
.
Bulk selection method
.
2-Back cross
3-Double cross
.
Marker assisted selection (MAS)•Marker-assisted selection (MAS) provides opportunities for enhancing the response from selection because molecular markers can be applied at the seedling stag•with high precision and reductions in cost
Molecular techniques
Marker assisted selection (MAS)
•For detecting single-major gene resistance, MAS could be easily applied• Marker-assisted selection is an efficient tool to speed up plant breeding. It helps also in pyramiding of resistance genes
Conventional Plant Breeding
Durable rust resistanceAgro-morphological traits Salt stress
P1 x P2
F1
F2
Susceptible Resistant
Conventional Plant Breeding
Durable rust resistanceAgro-morphological traits Salt stress
P1 x P2
F1
F2
Susceptible Resistant
(1) LEAF TISSUE SAMPLING
(2) DNA EXTRACTION
(3) PCR
(4) GEL ELECTROPHORESIS
(5) MARKER ANALYSIS
Overview of ‘marker
genotyping’
Wheat rusts, Catch it before it catches you
Thank you