SURVIVAL OF PHYTOPATHOGENIC BACTERIA
Phytopathogenic bacteria have the ability to survive both for longer & shorter periods including soil, seed, diseased crop debris, weed host, and insect vectors.
DISPERSAL OF PLANT PATHOGENIC BACTERIA
To make a healthy plant diseased, the first requirement of a pathogen is to spread its inoculum (primary as well as secondary) from the source of survival to the susceptible parts of a healthy plant. The spread of a plant pathogen within the general area in which it is already established is called “dispersal” or “dissemination”.
Moving the inoculum only a few inches and transporting it for hundreds of miles both constitute its dispersal or dissemination. However, pathogen dispersal is not necessary only for the spread of diseases but also for the continuity of the life-cycle and evolution of the pathogen. Detailed knowledge of pathogen-dispersal is essential to find out effective control measures for diseases because the possibilities of preventing dispersal and thereby breaking the infection chain always exist.
This power-point provides general knowledge on the major wheat disease as
Common bunt of wheat
Fusarium head blight of wheat
Loose smut of wheat
Stagonospora nodorum blotch of wheat
Bacterial streak of wheat
Barley yellow dwarf virus of wheat
Leaf rust of wheat
Stem rust of wheat
Stripe rust of wheat
Powdery mildew of wheat
Septoria tritici blotch of wheat
Stagonospora nodorum blotch
Tan spot
Wheat soilborne mosaic
Wheat spindle streak mosaic
Wheat streak mosaic
Cephalosporium stripe
Common root rot
Fusarium root,
crown, and foot rots
Take-all of wheat
This power-point provides general knowledge on the major wheat disease as
Common bunt of wheat
Fusarium head blight of wheat
Loose smut of wheat
Stagonospora nodorum blotch of wheat
Bacterial streak of wheat
Barley yellow dwarf virus of wheat
Leaf rust of wheat
Stem rust of wheat
Stripe rust of wheat
Powdery mildew of wheat
Septoria tritici blotch of wheat
Stagonospora nodorum blotch
Tan spot
Wheat soilborne mosaic
Wheat spindle streak mosaic
Wheat streak mosaic
Cephalosporium stripe
Common root rot
Fusarium root,
crown, and foot rots
Take-all of wheat
Symptoms of bacterial infection in plants are much like the symptoms in fungal plant disease.
They include
leaf spots,
blights,
wilts,
scabs,
cankers and a
soft rots of roots,
storage organs and fruit,
The most troublesome pests of paddy along with their control measures
For more information :
visit the link below:
http://infentfun.blogspot.in/p/blog-page_17.html
Symptoms of bacterial infection in plants are much like the symptoms in fungal plant disease.
They include
leaf spots,
blights,
wilts,
scabs,
cankers and a
soft rots of roots,
storage organs and fruit,
The most troublesome pests of paddy along with their control measures
For more information :
visit the link below:
http://infentfun.blogspot.in/p/blog-page_17.html
This includes detailed explanation with examples on diseases, disease cycle, its importance to study, types of disease cycle and pathogenesis including its components, like, means of survival, dispersal of the plant pathogens, inoculation, type of inoculum, pre-penetration, penetration including different means of entry of pathogens, post-penetration activities of the pathogens inside the plant host and its exit from the host.
Thirty soil borne viruses or virus like agents are transmitted by five species of fungal vectors i.e soil inhibiting fungi or protists.
Known vectors are from members of class Plamodiophoromycetes in the division Myxomycota & class Chytridiomycetes in the division Eumycota.
CHAPTER 15Smith, T. M., & Smith, R. L. (2015). Elements of Ecolo.docxcravennichole326
CHAPTER 15
Smith, T. M., & Smith, R. L. (2015). Elements of Ecology (9th ed.). Boston, MA: Pearson.
15.1 Parasites Draw Resources from Host Organisms
Parasitism is a type of symbiotic relationship between organisms of different species. One species—the parasite—benefits from a prolonged, close association with the other species—the host—which is harmed. Parasites increase their fitness by exploiting host organisms for food, habitat, and dispersal. Although they draw nourishment from the tissues of the host organism, parasites typically do not kill their hosts as predators do. However, the host may die from secondary infection or suffer reduced fitness as a result of stunted growth, emaciation, modification of behavior, or sterility. In general, parasites are much smaller than their hosts, are highly specialized for their mode of life, and reproduce more quickly and in greater numbers than their hosts.
The definition of parasitism just presented may appear unambiguous. But as with predation the term parasitism is often used in a more general sense to describe a much broader range of interactions (see Section 14.1). Interactions between species frequently satisfy some, but not all, parts of this definition because in many cases it is hard to demonstrate that the host is harmed. In other cases, there may be no apparent specialization by the parasite or the interaction between the organisms may be short-lived. For example, because of the episodic nature of their feeding habits, mosquitoes and hematophagic (blood-feeding) bats are typically not considered parasitic. Parasitism can also be used to describe a form of feeding in which one animal appropriates food gathered by another (the host), which is a behavior termed cleptoparasitism (literally meaning “parasitism by theft”). An example is the brood parasitism practiced by many species of cuckoo (Cuculidae). Many cuckoos use other bird species as “babysitters”; they deposit their eggs in the nest of the host species, which raise the cuckoo young as one of their own (see Chapter 12 opening photograph). In the following discussion, we use the narrower definition of parasite as given in the previous paragraph, which includes a wide range of organisms—viruses, bacteria, protists, fungi, plants, and an array of invertebrates, among them arthropods. A heavy load of parasites is termed an infection, and the outcome of an infection is a disease.
Parasites are distinguished by size. Ecologically, parasites may be classified as microparasites and macroparasites. Microparasites include viruses, bacteria, and protists. They are characterized by small size and a short generation time. They develop and multiply rapidly within the host and are the class of parasites that we typically associate with the term disease. The infection generally lasts a short time relative to the host’s expected life span. Transmission from host to host is most often direct, although other species may serve as carriers.
Macroparasite ...
A brief Power Point Presentation on disease cycle for students about their academics on professional level.
Content for this compilation (Power Point Presentation) was collected from Different sources: Internet, books, social media, research papers, websites etc. and acknowledged all these sources to provide such a helpful content.
This Presentation was prepared and presented during Bachelors In Agriculture (Session 2014-2018) at "University College of Agriculture and Environmental Sciences, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur (Pakistan)" as an Assignment on the topic of "The Disease Cycle" with the collaboration of Student fellows Muhammad Amir Shehzad and Muhammad Farhan.
I hope, content might be helpful for student on academic level.
Best Regards
Muhammad Raza Ullah Tariq
Case Study On Number Of Oral Cancer(Balasore, 2014).pdfOm Prakash
Oral cancer or mouth cancer, a type of head and neck cancer, is any cancerous tissue growth
located in the oral cavity.
The Case Study was conducted in 2014 as a part of an Investigatory Project Work on the Number Of Oral Cancel in the District of Balasore of Odisha in that Year
BANANA PACKAGE OF PRACTICE(Malayamal).pptxOm Prakash
Kerala is the land of a variety of bananas. There is a variety here that will surprise anyone. Most of the banana species are inextricably linked with our culture and customs. Bananas can also be grown as an intercrop in the available space. As it is rich in nutrients, the use of bananas is increasing both in the country and abroad.
Originating in Southeast Asia.
They are widely cultivated in more than 130 countries.
Banana occupies 12% of fruit area and 31% of production
About 107 million metric tons of bananas are produced in a year
Source of vitamin B, vitamin C, starch, protein, etc.
Major varieties of bananas.
Cultural Practices.
Tissue culture technique - advantages.
Banana pests.
Banana diseases.
Nutrition deficiency and toxicity.
Banana - vermicompost.
Banana - Thumburmuzhi Compost.
Product diversification.
Method of use for Pseudomonas fluorescens.
BBTV is the most serious virus disease of bananas and plantains. It occurs in Africa, Asia, Australia, and South Pacific islands. The virus is transmitted in a persistent, circulative, non-propagative manner by the banana aphid, Pentalonia nigronervosa, which has worldwide distribution. The virus is also spread through infected planting material. All banana cultivars are thought to be susceptible, with no known sources of resistance.
The typical symptoms of bunchy top of banana are very distinctive and readily distinguished from those caused by other viruses of banana. Infected plants exhibit a rosetted or ‘bunchy top’ appearance. Once infected, plants do not recover.
Cultural Disease Management Strategies.pptxOm Prakash
Cultural Disease Management
To reduce the dependence on chemical inputs in agriculture, eco-friendly approaches to the farming system like cultural practices for pest and disease management are most necessary. Cultural practices are the measures undertaken by humans to prevent and control the disease by manipulating plants. Cultural management can include reducing the amount of initial inoculum, reducing the rate of spread of established disease, or planting a crop at a site that is not favorable to pathogens because of its altitude, temperature, or water availability for disease management.
An interview is essentially a structured conversation where one participant asks questions, and the other provides answers. In common parlance, the word "interview" refers to a one-on-one conversation between an interviewer and an interviewee. The interviewer asks questions to which the interviewee responds, usually providing information. That information may be used or provided to other audiences immediately or later. This feature is common to many types of interviews – a job interview or interview with a witness to an event may have no other audience present at the time, but the answers will be later provided to others in the employment or investigative process. An interview may also transfer information in both directions.
BLASTOMYCETES
Members of this form class are characterized by yeast-like cells which propagate by budding.
A pseudomycelium may or may not be formed.
True mycelium is either lacking or is not well developed.
Most of the members are saprobes occurring on Flowers, wood, leaves, and barks.
Some of them occur in fresh and seawater.
• Some associated with the plant disease like powdery mildews, rusts, and smuts.
Anamorphic yeasts can be recovered from most ecological niches-animals, plants and their surfaces, fresh and marine water, soils, and environments such as manufacturing plants, tanning fluids, and mineral oils.
They comprise anamorphic (asexual or imperfect) yeast fungi that lack fruit bodies (conidiomata), have no dikaryophase, and are usually unicellular rather than filamentous.
The thallus consists of individual cells.
CLASSIFICATION
• Division-Eumycota
• Sub Division-Deuteromycota
• Class-Blastomycetes
The class Blastomycetes is divided into two orders
1. Sporobolomycetales
2. Cryptococcales
Approximately 80 genera comprising about 600 species are recognized.
The Integrated Disease Management (IDM) involves the need based use of pesticide only when the disease incidence reach economic threshold levels and this will promote the build up of many bio-control agent in the crop ecosystems.
Thus IDM, a greener alternative to the conventional use of chemicals, is an attempt to promote natural, economic and sociological farming methods through the most effective combination of farming techniques and judicious and limited use of fungicide.
In other words, IDM programme implies all the available disease management approaches including cultural, biological and chemical control with the main objective to keep the disease incidence below economic threshold level.
ATTRACTANTS & REPELLENTS IN PEST CONTROL.pptxOm Prakash
ATTRACTANTS
Chemicals which elicit oriented movements by insects towards their source are called
insect attractants. They influence both gustatory and olfactory receptors
REPELLENTS
Substances whose stimuli elicit avoiding reactions or chemicals that prevent insect
damage to plants or animals by rendering them unattractive, unpalatable or offensive
are called repellents.
Terminator technology refers to plants that have been genetically modified to render sterile seeds at harvest – it is also called Genetic Use Restriction Technology or GURTS
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
SURVIVAL AND DISPERSAL OF PHYTOPATHOGENIC BACTERIA.pdf
1. Presented By:
Om Prakash Barik
Adm. No. – 20222217
1st Yr. MSc. Ag. (Plant Pathology)
College Of Agriculture, OUAT, BBSR
ODISHA UNIVERSITY OF AGRICULTURE
AND TECHNOLOGY
College Of Agriculture, Bhubaneswar
PLANT BACTERIOLOGY
(Pl. Path 503) (2+1)
Assignment Topic:
SURVIVAL AND DISPERSAL OF
PHYTOPATHOGENIC BACTERIA
Submitted To:
Dr. Akshay Kumar Senapati
HOD & Professor
Dept. of Plant Pathology
College Of Agriculture, OUAT, BBSR
2. SURVIVAL OF PHYTOPATHOGENIC BACTERIA
Phytopathogenic bacteria have ability to survive both for longer & shorter
periods including soil, seed, diseased crop debris, weed host, insect
vectors.
1. Soil
Bacteria as transient visitors, resident visitors and residents.
Ttransient visitors: have no population increase and rapid population
decline in soll. Most of foliar effecting bacteria
For example, Xanthomonas campestris pv. campestris survives less
than 2 weeks in soil summer.
Rresident visitors: Pulations of resident visitors, such as soft rotting
Pantoea, Erwinia, decline gradually or they increase depending on
hosts.
Residents: Soft rotting bacteria pseudomonas and Bacillus spp.
maintain their population in soil.
2. Plant Debris
Contaminated plant debris serves as a means of survival of foliar
pathogens.
Duration of survival increases if this debris remains on the surface
rather than being buried deep in the soil.
Generally, the bacterial population decline sharply as the organic
residue decomposes and deep burial hastens decomposition through
providing moisture, temperature and other congenial conditions for
decomposition
E.g.,
Xanthomonas campestris pv. malvacearum can survive 40-100
days until the supporting cotton debris was thoroughly
decomposed
3. X. campestris pv. malvacearum could survive 6 months on the
soil surface and only 3 met when the cotton debris was buried
15 cm.
3. Seed
Seed acts as a means of survival for many bacterial plant pathogens.
Understanding the nature of seed infection is important if the
treatments are to eliminate pathogens.
The bacteria adhere to the seed coat, or lodged among the seed
hairs or may remain beneath the seed at or in deeper seed tissues.
E.g.,
X. campestris pv.campestris - Black rot of crucifers
X campestris pv.malvacearum - bacterial blight of cotton
X. oryzae pv.oryzae - bacterial blight of paddy
4. Insect – Vectors
Insect-vectors play important role both in disseminating as well as
over wintering the bacterial ant pathogens
The bacterium Pantoea stewarti can survive more than a month in
digestive tract of active corn flee beetle (Chaeronema pulicaria).
Psyringae pv. savastonoi (incitant of olive knot) can survive in the
digestive tract throughout the life of olive fruit fly.
The olive knot bacterium forms a significant part of intestinal
microflora; apparently, the bacterium makes host nutrients available
to the developing larvae
E.g.,
Pantoea stewartii lives in corn flea beetle digestive tract for
more than 1 month
P. syringae pv. savastonoi cause olive knot & can survive in
insect olive fruit fly for throughout the fruit fly life
4. 5. Weeds or collateral hosts, volunteer crop
Weeds or collateral hosts, volunteer crop plants play important role
in the survival of plant pathogenic bacteria. Solanum cineacum and S.
nigrum supports Ralstonia solanacearum. Many weed or non-host
plants support an epiphytic microbial population, which may include
plant pathogenic bacteria.
E.g.,
Xanthomonas campestris pv phaseoli is reported to urvive
epiphytotically on leaves of weeds hosts for up to 21 days. A
number of soil invading bacteria survive on the roots of non-
hosts or weed hosts.
Xanthomonas oryzae pv. oryzae cause bacterial leaf blight of
rice, it can survive on weeds like Leersia hexandra, Loryzoides
oryzoides var. japonica., Zoysia sp.., Echinochloa, crussgali,
Leptochloa chinensis, Cyperus rotundas.
Ralstonia solanacearum cause bacterial wilt of solanceous
plants can survive on Solanum nigrum & S. cineaeum for
throughout the life of weed
5. DISPERSAL OF PLANT PATHOGENIC BACTERIA
To make a healthy plant diseased, the first requirement of a pathogen is
spread of its inoculum (primary as well as secondary) from the source of
survival to the susceptible parts of healthy plant. The spread of a plant
pathogen within the general area in which it is already established is called
“dispersal” or “dissemination”.
Moving the inoculum only a few inches and transporting it for hundreds of
miles both constitute its dispersal or dissemination. However, the
pathogen-dispersal is not necessary only for spread of diseases but also for
continuity of the life-cycle and evolution of the pathogen. A detailed
knowledge of pathogen-dispersal is essential to find out effective control
measures for diseases because the possibilities of preventing dispersal and
thereby breaking the infection-chain always exist.
Dispersal of plant pathogenic bacteria generally occurs through two major
modes:
1. Autonomous (direct or active) dispersal and 2. Passive (indirect)
dispersal.
Mode # 1. Autonomous (Direct or Active) Dispersal:
In this case the pathogens get dispersed either by their own movement or
by the movement of the source they belong; no intervention of any
external agency like insects, air, water, etc. is involved. For instance,
autonomous dispersal of plant pathogens is accomplished through the
agency of soil, seed, plant and plant organs during normal agronomic
operations.
However, following are important modes of autonomous dispersal of plant
pathogens:
6. I. Seed Dispersal
The seeds generally serve as medium for autonomous dispersal of
pathogens when they either get contaminated with pathogens or
contain pathogens on their seed coats or contain them inside.
To exemplify autonomous dispersal of pathogens remaining intact on
seed coats, one can find diseases like bacterial black arm disease of
cotton or angular leaf spot of cotton (Xanthomonas campestris pv.
malvacearum) and black rot of crucifers (X. campestris pv. campestris)
where the pathogen remains dormant inside the seeds.
When such an infected seed is sown in next crop season and grows,
the pathogen also glows simultaneously systemically and the disease
manifests by symptoms appearing in plants.
II. Plant and Plant Organ Dispersal
Weeds and volunteer crop plants are known as source of survival and
dispersal of bacteria
Most of the solanaceous weeds harbor Ralastonia solanacearum and
Clavibacter michiganense and all sps. of brassica acts as host for
Xanthomonas campestris pv campestris.
Plants and their parts (other than seeds) prove to be good source of
pathogen dispersal. Plants generally get infected by the pathogen
already present in the field or introduced from outside.
There exist some classic examples of this type of pathogen dispersal
the new bacterial pathogen are often introduced into new areas with
the introduction new crops.
Psuedomonas syringae pv gplycinea was reported to be introduced
into united states and Russia with the introduction of soybean
culture from orient.
III. Soil Dispersal
Many of the pathogens survive through soil and get dispersed.
7. Mode # 2. Passive (Indirect) Dispersal:
The passive or indirect dispersal of plant pathogens is accomplished
through the intervention of external agencies like air, water, man, insects,
nematodes, farm and wild animals, birds, and fungi.
I. Air Dispersal (Anemochory)
Aerial strands- Many plant pathogenic bacteria exudates ooze or
slime on diseased tissue. This strands break apart into fine fragments
which then carried by dry wind to another host plant Example
Psuedomonas syringae pv mori bacterial blight of mulberry.
Wind driven rain - The bacteria dispersed along the contaminated
water particles driven by wind. Example Clavibacter michiganense
subsp. michiganense tomato cancker
Wind driven soil particles or dust - Example- Streptomyces scabies
potato scab
Aerosol carrying bacteria deposits directly onto soybean leaves of
P. Syringae pv. glycinea bacterial blight of soybean.
II. Water Dispersal (Hydrochory)
Water as an agent of plant pathogen dispersal appears in no way less
important to air, man, and insects. It generally provides for short
distance dispersal except when floods inundate large areas.
Water-splash dispersal is one of the very efficient device by which
rain spreads plant pathogens; rain drops falling with force on
pustules, cankers, or even soil surface may splash the pathogens in
small droplets and enable them to land on neighboring healthy
susceptible host surfaces or such water droplets, may be carried to
long distances by water splash
8. E.g.,
P. syringae pv.syringae brown spot of bean weed host (as
epiphyte) to the natural host by rain splash.
P. avenaenlade blight of oats upward movement of bacteria
from soil to leaves by scattering rains.
Water-flow dispersal is known to disseminate bacteria through Irrigation
water or rain water from an infested field may carry with it pathogens to
neighboring fields of healthy crops. In 1963, epidemic occurred on about
506ha of peas under sprinkler irrigation in Wisconsin due to bacterial
blight of peas caused by P. syringae pv. pisi.
III. Dispersal by Man (Anthropochory)
Man is one of the most important agents affecting plant pathogen
dispersal in a limited area or even over distant areas.
Short Distance:
Pathogen dispersal by man in limited areas mainly occurs through his
clothes, contaminated tools, transport of contaminated soil on feet,
equipment, etc.
Grafting and budding between healthy and diseased plants, and
cultural operations such as hoeing, weeding, pruning easily spread
pathogens from one plant to the other.
Long Distance:
The dispersal of plant pathogens over long distances is usually
accomplished by the transport of infected plant parts such as seeds,
nursery stocks, or timber products; the seed trade is actually the
means of dispersal in which man plays the most crucial role.
The import and export of pathogen containing materials without
prior precautions lead to movement of pathogens from one country
to the other.
9. E.g.,
Bacterial
Pathogen
Disease Introduce Into
Introduce
From
X.c.pv.campastris
Black rot of
crucifers
India in1929 Jawa
X.oryzae pb.
oryzae
Bacterial blight
of rice
India in1959 Philippines
X. citri Citrus canker United states Japan
Erwinia
amylovora
Fire blight of
stone fruits
Japan, New
Zealand,
Europe in 1919
North
America
P. Syringae pv
glycinea
Bacterial blight
of soybean
United states
and Russia
Orient
IV.Dispersal by Insects
Since the discovery by Waite (1891) shows that bees and wasps
disseminate bacteria Erwinia amylovora (causing fire blight of apple
and pear), insects have been found to be one of the most important
agents for plant pathogen dispersal.
Often insects transmits bacteria as contaminants during their feeding,
foraging, or nectar/pollen collecting activities.
For instance, Insects are considered important for dispersal of some
bacterial pathogens.
E.g.,
The cucurbit-wilt causing bacterium, namely Erwinia
tracheiphila is completely dependent on cucumber beetles for
its dispersal.
Erwinia carotovora causes black leg disease of potato is
disseminated by insects mainly Hylemya cilicrura.
10. Pantoea stewartii, the corn wilt pathogen, perennates inside
Chaetocnema pulicaria (corn flea beetle) in their digestive
tract and is spread by the latter.
Leaf minor insect disseminates Xanthomonas campestris pv.
citri, the causal organism of well-known citrus canker disease.
V. Dispersal by Nematodes
Nematodes play an important role in disseminating. Although they
favor only short distance or local dissemination.
Leafy gall disease caused by Corynebacterium fasciens is dispersed by
Aphelenchoides, an ectoparasitic nematode. Yellow carrot disease of
wheat caused by Corynebacterium tritici is disseminated by the ear
cockle nematode, namely, Anguina tritici.
VI. Dispersal by cultural practices
As contaminant on agriculture implements there are certain cultural
practices that are responsible for bacterial pathogen dispersal.
For instance Clavibacter michiganense pv. sepedonicus causing ring
rot of potato spread to non-infected potato see on cutting knives
contaminated with infected tubers.