1. DEPARTMENT OF GENETICS AND
PLANT BREEDING
FACULTY OF AGRICULTURE
ANNAMALAI UNIVERSITY
GPB-517 GERMPLASM CHARACTERIZATION AND
EVALUATION(1+1)
EVALUATION OF BIOTIC RESISTANCE TRAITS-GENETIC-
BIOCHEMICAL-MOLECULAR MARKERS
SUBMITTED BY
VIKRAMAN.A
2251150005
2. BIOTIC STRESS :
Biotic stress is stress that occurs as a result of damage
done to plant by other living organisms, such as bacteria,
viruses, fungi, parasites, beneficial and harmful insects,
weeds and cultivated or native plants.
BIOTIC STRESSES IN PLANTS :
⮚Weeds
⮚Insects
⮚Fungi
⮚Bacteria
⮚Virus
3.
4. BIOTIC RESISTANCE
►Biotic resistance is the ability of species in
a community to limit the invasion of other
species
►But Biotic resistance not widely used to
invasive plants
►The defences to biotic stresses include
morphological and structural
barriers,chemical compounds proteins
and enzymes
5. GENETIC BASIS OF DISEASE
RESISTANCE
►Genetic analysis of disease resistance in plants
began over 100 years ago when Biffin (1905)
reported that resistance in wheat to stripe rust
was inherited as a single recessive Mendalian
trait.
►In genetic terms, resistance is generally defined
by mode of inheritance, with broad distinction
between oligogenic and polygenic resistance.
6. GENE FOR GENE HYPOTHESIS
⮚The concept of gene for gene hypothesis was
first developed by Flor in 1956 based on his
studies of host pathogen interaction in flax or
linseed (Linumussitaticimum)
for rust caused by Malampsoralini.
⮚For each gene controlling resistance in the host,
there is a corresponding gene controlling the
pathogenicity in the pathogen.
⮚MODELS : 1. Single gene for gene hypothesis
2. Double gene for gene
hypothesis
7. DISEASE RESISTANCE :
Ability of a host to restrict or even prevent the
production of disease symptoms on invasion of
pathogen due to presence of resistance genes.
TYPES :
1) Vertical Resistance (OLIGOGENIC
RESISTANCE) :
⮚Controlled by major genes (one or two).
⮚Genes are readily transfer from one gene to other.
⮚Example – Leaf rust resistance in wheat.
8. 2) HORIZONTAL RESISTANCE (POLYGENIC
RESISTANCE ) :
⮚ Controlled by many genes each with minor
effects.
⮚ Can control a broad range of races due to
the fact that many loci are Involved.
⮚ Difficult to transfer resistance from one
genotype to other.
⮚ Individual genes harder to identify.
⮚ Example : Fusarium head blight in wheat.
9. Mechanism of disease resistance in
plants
►Disease escape
►Tolerance
►Immunity
►Hypersensitivity
►Production of antimicrobial metabolites
►Synthetic enzymes(e.g – Chitinases, glucanases)
10. ►Distinct classes of resistance and susceptible plants.
►Controlled by one or few genes.
►Also called vertical resistance.
►High efficiency in specific race.
QUANTITATIVE RESISTANCE
►Continuous variation among genotyes.
►Many loci.
►Also called Horizontal resistance.
►Efficiency variable against all race.
QUALITATIVE RESISTANCE
11. SOURCES OF DISEASE RESISTANCE
►Known variety
►Wild relatives
►Related species
►Mutations
►Unrelated organisms
12. BIOCHEMICAL RESISTANCE :
► The biotic stress constantly affects the agro eco system
which includes viruses, mycoplasma, bacteria,
fungi,weeds and insects which directly affect the soil
health and productivity of crops.
► Among the all processes, components of biochemical
pathways play a vital part in safeguarding plants.
► Pathogenic resistance
► insect resistance
► weed resistance
13. Plant to Pathogenic biochemical
resistance
► In general, when there is no stress, the plants exhibit
optimal growth and development by using the available
oxygen. However, during stress like pathogen attack, low
usage of oxygen results in the production of reactive
oxygen species in plant tissues, which in turn causes photo-
oxidative damage to biomolecules and the internal
cellular structures.
► The plants respond to such interaction of microbes by
inducing a plethora of biochemical changes associated
with stress signaling and thus activating their defense
pathways.
14.
15. The induced defense mechanism includes
various non-enzymatic components
comprising :
► Phenolic compounds,
► Flavonoids,
► Lignins and
► Enzymes for phenol metabolism like phenylalanine ammonia-
lyase (PAL), polyphenol oxidase (PPO) and antioxidant
enzymes like superoxide dismutase (SOD), catalase (CAT),
peroxidases (POX) and glutathione reductase (GR)
accumulation of tannins and phyto alexin
16. Plant disease resistance genes - During the plant-
pathogen interaction
► The plant releases several types of elicitors. These elicitors
are recognized by plant resistance genes and trigger
various biochemical and physiological changes in plant
Plant defense system against plant pathogens
► In natural habitats, plant defense systems serve a pivotal
role in safeguarding plants against pathogens and in
nutrient mobilization. In addition to self-defense of plants,
useful microbes and plant growth-promoting rhizobacteria
also activate the defense mechanism via two different
pathways, systemic acquired resistance (SAR) and induce
systematic resistance (ISR) .
17. PLANT TO INSECT BIOCHEMICAL RESISTANCE :
► Insects causes varietal damages to plants that affect the
yield.
► Biochemical resistance is mediated through chemicals
produced by the plant.
► These chemicals are harmful to insects and reduce their
use of certain plants. plant species include proteinase
inhibitors in their tissues, which inhibit the action of
digestive enzymes in the insect.
► Plants also create compounds that are toxic to insects.
Quinones, a type of phenol compound, both inhibit
protein breakdown in insects and can have direct, toxic
effects on some insect species.
19. MOLECULAR MARKER IN BREEDING
►Molecular marker may be defined as any
site(locus) in the genome of an organism at
which the DNA base sequence varies among
the different individuals of a population.
►Such markers generally have no apparent
effect on the phenotype of the individual.
20. TYPES
Most common types of markers used are
► RFLP - Restriction fragment length polymorphism
► RAPD - Random amplification of polymorphic DNA
► AFLP - Amplified fragment length polymorphism
► SSLP - Simple sequence length polymorphism DNA
► VNTR - Variable number tandem repeats
SSR – Simple sequence repeat
SNP – Single nucleotide po;ymorphism
STR - Short tandem repeat
21. MARKER ASSISTED SELECTION FOR
BIOTIC RESISTANCE
❖ Through MAS successful pyramidization of genes/QTLs to
confer resistance/tolerance to blast(pi2,pi9),gall midge
(Gm1,Gm4), in a released rice variety CRMAS2621-7-1
AS Improved Lalat.
❖ In rice allele for root depth has been intorgressed to IR
64 From Azucena (Shen et al, 2001).
❖ In rice genotype Lalat improved Lalat for Bacterial
blight ( Xa4 + Xa5 + Xa13 + XA21). Dokku et al.,2013
22. ► In bread wheat locus Kna1 determining K/Na ratio is
linked to 5 RFLP marker on 4D long arm. Gurham et
al.,1997.
FUTURE PROSPECTIVES :
❖Identifying and exploiting new genes from tolerant
sources.
❖Marker assisted selection do efficient screening.
❖Identify QTL linked to biotic stress resistant genes
and pyramiding of genes / QTL genes with minor
effects.
