Phytophthora: Destructive Plant Pathogen
PHYTOPHTHORA
Pinaki Kr. Rabha
J.N.College, Boko
•
It is one of most destructive plant pathogen.
•
It infects a number of angiospermic cultivated
crops including potato, tomato, colocasia,
areca nut, etc.
•
The fungus is responsible for destruction of
potato crops in Ireland in 1840s resulting
famine and death of over a million people.
Symptoms of the disease
•
The development of leaf rots or lesions varies
with environmental conditions.
•
Leaf lesions begins as small, irregularly
shaped, light green to grey spots.
•
In cool (20o
C or less), moist environments,
lesions expand rapidly to form a large black rots
that spread the entire plants.
•
Infection on underground tubers is first seen
in the form of dry rot and brown
discolorations of the tissues.
•
In the later stages the infection spreads
inwards, the entire tuber becomes brown and
ultimately gets decayed.
Somatic structure:
It is profusely branched and consists of aseptate,
hyaline, coenocytic hyphae . The mycelia are both
inter and intracellular.
Asexual reproduction:
Asexual reproduction is brought about by
zoospores. They are produced within
sporangium. Sporangiophores emerge from the
lower surface of leaves through stomata and bear
terminal, lemon shaped sporangia with distinct
papilla. The renewed growth of the
sprangiophore gives it a zigzag, sympodial shape.
Asexual reproduction
Germination of sprangia:
The sprangia are disseminated by wind and soil water. The
germination of sporangia depends upon temperature.
Indirect germination:
Low temperature favors for indirect germination of
sporangia. The protoplasm of the sporangium divides into
several uninucleate protoplasts. Each protoplast
metamorphoses into a biflagellate, reniform, uninucleate
zoospore. The sporangia bursts at the papilla and the
zoospores are liberated. The liberated zoospores are
deflagellated, then encyst and finally germinate to form a
new hypha.
Asexual reproduction
Direct germination
:
In high temperature and dry conditions, the
sporangia behaves like as conidia and
germinate directly by forming multinucleate
germ tube.
Sexual Reproduction
In Phytophthora sexual reproduction is
oogamous. It is infrequent in P. infestans as it is a
heterothallic species.
On the basis of the position of sex organs, the
species of Phytophthora are designated as
paragynous
or
amphigynous
. In paragynous type
(P. cactora), the sex organs lie laterally, while in
the amphigynous type (P. infestans and P.
colocasiae),the antheridia forms a funnel or coller
shaped structure at the base at the oogonium.
The oogonium is initially multinucleate, at
maturity contain a single nucleus. The
protoplasm at the centre of the oogonium is
called ooplasm, which contain the female
nucleus and serve as female gamete.
The antheridium is club shaped. At maturity it
contains a single male nucleus. The male
nucleus reaches the ooplasm through a
fertilization tube formed by the antherium.
Plasmogamy followed the karyogamy, results
in a diploid zygote nucleus. It is surrunded by
a wall and converted into oospore. After a rest
period, it germinates and forms a
zoosporangium at the tip of the germ tube.
Zoospores of two mating types are found in
equal numbers, which give rise to thalli of
opposite mating types.
Sexual reproduction
Life cycle
Phytophthora is a destructive plant pathogen that infects various crops, causing symptoms like leaf lesions and rotting tubers. Its somatic structure includes profusely branched hyphae, and it reproduces asexually through zoospores. The germination process involves the spread of spores by wind and water, influenced by temperature. Learn more about this devastating fungus and its impact on agriculture.
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Presentation Transcript
PHYTOPHTHORA Pinaki Kr. Rabha J.N.College, Boko
It is one of most destructive plant pathogen. It infects a number of angiospermic cultivated crops including potato, tomato, colocasia, areca nut, etc. The fungus is responsible for destruction of potato crops in Ireland in 1840s resulting famine and death of over a million people.
Symptoms of the disease The development of leaf rots or lesions varies with environmental conditions. Leaf lesions begins as small, irregularly shaped, light green to grey spots. In cool (20oC or less), moist environments, lesions expand rapidly to form a large black rots that spread the entire plants.
Infection on underground tubers is first seen in the form of discolorations of the tissues. In the later stages the infection spreads inwards, the entire tuber becomes brown and ultimately gets decayed. dry rot and brown
Somatic structure: It is profusely branched and consists of aseptate, hyaline, coenocytic hyphae . The mycelia are both inter and intracellular. Asexual reproduction: Asexual reproduction zoospores. They are sporangium. Sporangiophores emerge from the lower surface of leaves through stomata and bear terminal, lemon shaped sporangia with distinct papilla. The renewed sprangiophore gives it a zigzag, sympodial shape. is brought produced about by within growth of the
Germination of sprangia: The sprangia are disseminated by wind and soil water. The germination of sporangia depends upon temperature. Indirect germination: Low temperature favors for indirect germination of sporangia. The protoplasm of the sporangium divides into several uninucleate protoplasts. metamorphoses into a biflagellate, reniform, uninucleate zoospore. The sporangia bursts at the papilla and the zoospores are liberated. The liberated zoospores are deflagellated, then encyst and finally germinate to form a new hypha. Each protoplast
Direct germination: In high temperature and dry conditions, the sporangia behaves like germinate directly by forming multinucleate germ tube. as conidia and
Sexual Reproduction In Phytophthora oogamous. It is infrequent in P. infestans as it is a heterothallic species. On the basis of the position of sex organs, the species of Phytophthora are designated as paragynous or amphigynous. In paragynous type (P. cactora), the sex organs lie laterally, while in the amphigynous type (P. infestans and P. colocasiae),the antheridia forms a funnel or coller shaped structure at the base at the oogonium. sexual reproduction is
The oogonium is initially multinucleate, at maturity contain a protoplasm at the centre of the oogonium is called ooplasm, which contain the female nucleus and serve as female gamete. The antheridium is club shaped. At maturity it contains a single male nucleus. The male nucleus reaches the ooplasm through a fertilization tube formed by the antherium. single nucleus. The
Plasmogamy followed the karyogamy, results in a diploid zygote nucleus. It is surrunded by a wall and converted into oospore. After a rest period, it germinates zoosporangium at the tip of the germ tube. Zoospores of two mating types are found in equal numbers, which give rise to thalli of opposite mating types. and forms a
Sexual reproduction Phytophthora infestans
Graphic representation of the life cycle of phytophthora with zygotic meiosis
