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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

(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

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