Survival and dispersal of important plant pathogen
1. SURVIVAL AND DISPERSAL OF IMPORTANT
Department of Plant Pathology
Bihar agricultural university
Sabour , Bhagalpur (813210)
Dr. Amarendra Kumar
In the absence of their cultivated host, the pathogens
must be find some alternates source of their survival
to maintain the infection chain.
The means of survival are the first link in the
infection chain or the disease cycle. The initial
infection that occurs from these sources in the crop
are called primary infection and the propagules are
called primary inoculum.
After initiation of the disease in the crop, the spores
or cells or other structures of the pathogen are
sources of secondary inoculums and cause secondary
infection. The primary infection initiate the disease
and secondary infection spread the disease.
4. SURVIVAL OF PLANT PATHOGENS
1.Infected host as
reservoir of primary
survival of fungal
of fungal pathogens
as source of survival
SURVIVAL OF FUNGAL
Eg. Yellow rust
Eg. Stem rust-
INFECTED HOST AS
RESERVOIR OF PRIMARY
6. In the absence of the living host ,the facultative parasites
are capable of surviving as saprophytes. Soil and plant
debris serve as media for this saprophytic survival. Spp.
Of Pythium, Sclerotium etc. resting structure like oospores
and sclerotia .In Pythium aphanidermatum( foot rot of
papaya), the fungus rapidly forming oospores. S. rolfsii,
Sclerotia are formed and these can germinate under
P. aphanidermatum Sclerotia
7. DORMANT ORGANS OF FUNGAL PATHOGENS AS SOURCE OF SURVIVAL AND PRIMARY
(1)Soil borne fungi:-a.dormant
b.other dormant structure such as thickened hyphae and
(2)Seed borne fungi:-a.dormant
spores on seed coat
b.dormant mycelium and spores
under the seed coat or in the
8. (3)Dormant fungal structures including dead plant
parts remaining on the trees.
P. brassicae survive through its resting spores lying free
or in crop debris in the soil for upto 10 years. S.
subterranea survive through spores balls.Pythium
,Phytophthora and albugo are produced dormant
structure oospores and conidia
Plasmodiophora plant debries Phytophthora on dead plant
9. SURVIVAL OF
Transient visitors and
4. WITH INSECT
No resting spores
in such genera as
endospores or in
S. scabies which
12. DISPERSAL OF PLANT
Transport of spores or infectious bodies, acting as
inoculum, from one host to another host at various
distances resulting in the spread of the disease.
Displacement of a plant pathogen from its
place of production or origin to a suitable
place where it can grow/establish.
13. SPORE LIBERATION(TAKE OFF)
Squirt gun mechanism:-Ascus swells at
maturity and brust at the tip in air.
Rounding off mechanism:- Top of
sporophore rounded off and ejected into air.
Mechanical momentum:-Through rain drop
Blowing away:-Rust uredospore.
14. SPORE LANDING(DEPOSITION)
Sedimentation:-Under the influence of gravity.
Dispersal of plant pathogen are mainly consist of two
method viz. active and passive dispersal.
Active dispersal:- No need any type of external
energy for dispersal of plant pathogen.
By soil:-Pythium and phytophthora form zoospores
can swim with water in the soil, Actinomycetes,
Synchytrium and Fusarium can also grow in the soil.
15. By seed:-Cuscuta, sclerotia of ergot fungi,
ear cockle and cyst containing nematode.
Pathogen present in seed coat such as smut
of bajra, karnal bunt of wheat, bunt of rice
and leaf smut of rice ,BLB etc.
Pstv are transmit by pollen.
By plant organ:- Mostly in vegetative
propagated plant such as black wart potato,
late blight of potato, citrus canker etc.
16. Passive dispersal:-This type of dispersal are
done by the help of any type of external energy
such as animals, insects, and nematode etc.
Animals:-Through vegetative propagation such
as late blight of potato, bacterial wilt of banana,
sigatoka disease of banana etc.
Insects:- Cucurbit wilt(E. Trachiephila-spoted
cucumber beetle-Diabrotica undecimpunctata),
dutch elm disease-Ceratostomella ulmi etc.
Nematode:-Yellow ear rot of wheat-
Rathayibacter tritici, grape fan leaf-xiphinema,
nepo-longidorus, tobra-trichodorus etc.
17. Surface running water
after heavy rains
Long distance ------ floods
Ex: The mycelial fragments, spores or sclerotia of
fungi,Colletotrichum , Fusarium, Macrophomina,Pythium,
Phytophthora, Sclerotium, etc.,
DISPERSAL BY WIND
Short distance dissemination
sporangia of downy mildew fungi, conidia of
powdery mildew fungi and basidiospores of rust
Long distance dessimination
Uredospores of rust fungi, Chlamydospores of
smut fungi conidia of Alternaria, Helminthosporium
and Pyricularia, etc.