Methods for identifying plant diseases include checking for symptoms on specific plant parts, looking for signs of causal agents like fungal spores, and determining if symptoms are found across plant species or isolated to one. Modern molecular techniques allow for precise diagnosis, such as polymerase chain reaction (PCR) which amplifies DNA to detect bacteria, fungi and viruses through primer specificity. Other techniques are LAMP using multiple primers, RAPD analyzing DNA fragment polymorphisms, RFLP comparing fragment lengths after restriction enzyme digestion, and microarrays where probes detect complementary DNA sequences.

1. Methods for identification of plant diseases
Check for the symptoms:
Variation in symptoms in diseased plants may sometimes
lead to improper
Diagnosis..
Look for signs of disease
causal agents:
and spore-producing
bodies.
•Signs may include the
mycelia of a fungal
agent, fungal spores,
Identify plant part Affected: The symptoms
of some diseases are most commonly seen on
specific plant parts.
Check distribution of symptoms:
how the diseased plants are
distributed over the affected area
Check for host
specificity: Is the
problem occurring in
only one plant species or
are different plant
species .

2. Different techniques In Molecular Diagnosis
Polymerase Chain
Reaction (PCR)
PCR is used in the
diagnosis of plant
diseases has become
very common in
laboratory practice.
Efficiency for detection
of bacteria, fungi and
viruses is based on the
primer specificity.
LAMP A set of four specifically designed
primers.
Recognize six distinct sequences of the
target.
The amplification products.
Random Amplified
Polymorphic DNA (RAPD)
using short
usually 10
nucleotide
primers.
Polymorphi
sm of
amplified
fragments.
substitutio
ns or
deletions in
the priming
sites.

3. Restriction Fragment Length Polymorphism
(RFLP)
•Is a difference in homologous DNA
sequence.
•detected by the presence of fragments of
different lengths.
•after digestion of the DNA samples in
question with specific restriction
endonucleases.
Microarray
Technology
composed of
thousand of
specific probes
spotted onto a
solid surface.
Each probe is
complementary
to a specific DNA
sequence.
a signal that can
be detected and
analyzed.