LIFE CYCLE OF PYRICULARIA

1. Symptoms,host range,taxonomy and
life cycles of pyricularia(Magnoporthe)
Athira rajan
athirarajanmt@gmail.com

2. Pyricularia
• Pyricularia is a genus of fungi which was named by Saccardo in 1880
• The polyphyletic nature
of Pyricularia has been resolved and
species of Pyricularia , were shown to
belong to a monophyletic clade
(including Pyricularia grisea isolates),
defining the family Pyriculariaceae

3. SCIENTIFIC CLASSIFICATION
kingdom Fungi
division Ascomycota
subdivision Pezizomycotina
class Sordariomycetes
subclass Sordariomycetidae
Order Magnoporthales
Family Magnoporthaceae
genus Pyricularia
Sacc.1880

4. ETYMOLOGY
• The genus Pyricularia is named after
the pyriform (pear-shaped) shape of
its conidia
• Conidia are solitary, pyriform to
obclavate, narrowed toward tip, rounded
at the base, 2-septate, hyaline to pale
brown, with a distinct basal hilum,
sometimes with marginal frill Pyricularia oryzae

5. • M. oryzae is distinct from M.
grisea, a species that is
morphologically indistinguishable
from M. oryzae, a species that
affects crabgrass (Digitaria)
SEXUAL MORPHS
• Sexual morphs were reported
for P. grisea and P. oryzae. The
genus Pyricularia comprises
several other species for which
the sexual morph has not yet been
discovered
Magnaporthe grisea

6. PATHOGENECITY AND HOST RANGE
• The genus Pyricularia includes species that are pathogenic on
a wide range of monocot plants, major diseases on grasses
• Pyricularia oryzae (sexual morph Magnaporthe oryzae), the
causal agent of the rice blast disease, is one of the most
widely distributed diseases of rice, and is highly destructive
leading to up to 30% yield loss worldwide

7. PATHOGEN: Magnaporthe oryzae
Previously, Magnaporthe grisea
Pyricularia oryzae is the asexual name
HOSTS: Rice (Oryza sativa)
RICE BLAST DISEASE

8. SYMPTOMS AND SIGNS
• However, the most common and diagnostic symptom, diamond
shaped lesions, of rice blast occur on the leaves, whereas lesions
on the sheaths are relatively rare
• The symptoms of rice blast include lesions that can be found on
all parts of the plant, including leaves, leaf collars, necks,
panicles, pedicels, and seeds

9. Diamond-shaped spots on the leaves
of rice leaves caused by
blast Magnaporthe oryzae.
Infections at the nodes of stems
below the neck, caused by blast,
Magnaporthe oryzae. The
infections occur beneath the flower
head and can lead to death of the
stem

10. o RICE LEAVES
The symptoms on leaves may vary according to
the environmental conditions, the age of the plant,
and the levels of resistance of the host cultivars
On susceptible cultivars, lesions may initially
appear gray-green and water-soaked with a darker
green border and they expand rapidly to several
centimeters in length

11. o RICE COLLARS
Collar infections can kill the entire leaf and
may extend a few millimeters into and around
the sheath. The fungus may produce spores on
these lesions
o RICE SEEDS
Symptoms of rice blast on seeds themselves
consist of brown spots, blotches and
occasionally the classic diamond-shaped
lesion often seen on leaves

12. o RICE NECKS AND PANICLES
•Necks are often infected at the node by the rice blast
fungus and infection leads to a condition called rotten neck
or neck blast
•Infection of the necks can be very destructive, causing
failure of the seeds to fill (a condition called blanking) or
causing the entire panicle to fall over as if rotted

13. • Lesions can be found on the panicle branches, spikes, and
spikelets. The lesions are often gray brown discolorations
of the branches of the panicle, and, over time, the
branches may break at the lesion.

14. LIFE CYCLE
• The rice blast fungus starts its infection cycle when a three-celled
conidium lands on the rice leaf surface
• The spore attaches to the hydrophobic cuticle and germinates,
producing a narrow germ tube
• These subsequently flattens and hooks at its tip before
differentiating into an appressorium
• The single-celled appressorium matures and the three-celled
conidium collapses and dies in a programmed process that requires
autophagy

15. • The appressorium becomes melanized and develops
substantial turgor
• This translates into physical force and a narrow penetration at
the base
• puncturing the cuticle and allowing entry into the rice epidermis.

17. THANK YOU