Includes importance of knowing about vector interactions with hemipteran insects and plants for successful management of vector borne bacterial diseases in plants
4. UNIVERSITY OF HORTICULTURAL SCIENCES BAGALKOT
08-04-2024 Dept. of PAT 4
COLLEGE OF HORTICULTURE, BAGALKOT
SEMINAR – I
Vector-borne bacterial plant pathogens: Interaction with hemipteran
insects and plants
Name of the Student : Manohar Gowda B P
ID. No. : UHS22PGM1531
Degree Programme : Sr. M.Sc
Department : Plant Pathology
5. 08-04-2024 Dept. of PAT 5
Introduction
Vector borne bacteria
Case studies
Conclusion
Bacteria and Vector
Hemiptera
Vector Born plant pathogen
Relationship
Flow of Seminar
Phloem Limited
Xylem Limited
6. 08-04-2024 Dept. of PAT 6
Plant pathogenic bacteria
(Perilla-Henao et al., 2012)
7. 08-04-2024 Dept. of PAT 7
Transmission
Direct Indirect
(Perilla-Henao et al., 2012)
8. 08-04-2024 Dept. of PAT 8
Direct
Seed transmission Physical contact
Infected planting material Vegetative propagation
Natural openings
(Perilla-Henao et al., 2012)
9. 08-04-2024 Dept. of PAT 9
Indirect
Wind Water
Human Insects
(Perilla-Henao et al., 2012)
10. Efficient transmission
Long-distance spread
Diverse range of hosts
Symbiotic association
4/8/2024
10
Insect vector
Insect vectors play a crucial role in the transmission of plant
pathogens due to
(Perilla-Henao et al., 2012)
16. XYLEM PHLOEM
Plant vascular system-
xylem and phloem
Rich source of nutrients
Pipeline between source
and sink
Bacteria, virus and insects
depend on xylem and phloem
Xylella
Ca.Phytoplasma
Liberibacter
Spiroplasma
Nutrient pool
08-04-2024 Dept. of PAT 16
(Will et al. , 2013)
17. Firmicutes Actinobacteria Proteobacteria
Bacilli Clostridia
Mollicutes Alphaproteobactera
Betaproteobacteria
Gammaproteobactea
Spiroplasma Phytoplasma
Liberibacter Xylella
Passengers – vector borne pathogens
Bacteria
08-04-2024 Dept. of PAT 17
(Perilla-Henao et al., 2012)
18. Spiroplasma
08-04-2024 Dept. of PAT 18
DISEASES
Pierce’s disease of grapevine
Olive quick decline syndrome
Citrus variegated chlorosis
Almond leaf scorch
Vector-Sharpshooter , leafhopper and
Spittlebugs
DISEASES
Corn stunt disease
Citrus stubborn disease
Periwinkle yellows disease
Vector-Leafhoppers
Xylella
(Perilla-Henao et al., 2012)
19. 08-04-2024 Dept. of PAT 19
DISEASES
Huanglongbing/Citrus greening
Zebra chip
Tomato psyllid yellows
Vegetative disorders and carrot
yellows
Vectors-Psyllids
DISEASES
Aster yellows
Big bud
Apple proliferation
Coconut lethal yellowing
Peach X disease
Vector- Leafhoppers, Plant hoppers
and Psyllids
Phytoplasma
Liberibacter
(Perilla-Henao et al., 2012)
23. 08-04-2024 Dept. of PAT 23
Induced release of a plant- defence volatile ‘deceptively’ attracts
insect vectors to plants infected with a bacterial pathogen
Rajinder S. Mann , Jared G. Ali , Sara L. Hermann , Siddharth Tiwari , Kirsten S. Pelz-Stelinski , Hans T.
Alborn , Lukasz L. Stelinski
University of Florida,United States of America
To determine pathogen infection alters the attractiveness of host plants to the vector
1 NAAS Rating :-9.70
OBJECTIVE:
24. 08-04-2024 Dept. of PAT 24
Host plant : Citrus
Disease : Huanglongbing disease (Citrus greening)
Pathogen : Candidatus Liberibacter asiaticus
Vector : Diaphorina citri (psyllid)
Location : University of Florida, USA
Response of psyllids to host plant odours
Feeding efficiency of D. citri on non-infected and infected plants
Nutritional status of Las-infected and non-infected citrus plants
Volatile release by Las-infected and non-infected citrus plants
Observations
(Mann et al., 2012)
Material and methods
25. Fig. 1: Response of D. citri to odors emitted from Las-infected versus non-infected citrus
in a laboratory olfactometer
08-04-2024 Dept. of PAT 25
(Mann et al., 2012)
26. 08-04-2024 Dept. of PAT 26
Fig. 2: Feeding efficiency of D. citri on Las-infected versus non-infected citrus leaves as
measured by honeydew excretion
(Mann et al., 2012)
27. 08-04-2024 Dept. of PAT 27
Table 1. Differing levels of various nutrients between Las-infected and non-infected Citrus
sinensis plants
(Mann et al., 2012)
28. 08-04-2024 Dept. of PAT 28
Fig. 3: Chromatograms displaying volatile differences between Las-infected and
non-infected plants
(Mann et al., 2012)
29. 08-04-2024 Dept. of PAT 29
INFERENCE
Initially, the Las-infected plants were more attractive to D. citri adults than
non-infected plants after the acquisition of the Las by psyllids healthy plants
are more attractive than the Las infected
Host selection behaviour of D. citri may be modified by bacterial infection of
plants which, alters release of specific headspace volatiles and plant nutritional
contents.
(Mann et al., 2012)
31. 08-04-2024 Dept. of PAT 31
Xylella fastidiosa
Aerobic
Gram-negative, rod-shaped
Bounded by cell wall and cell membrane
Lack flagella
Forms a biofilm-like layer within xylem cells
Transmitted exclusively by xylem sap-feeding insects such
as sharpshooters and spittlebugs
X. fastidiosa can be found in about 600 different plant species
32. X. fastidiosa - Pierce’s disease (PD) (grapevine)
X. fastidiosa ssp. multiplex - Almond leaf scorch (ALS) and diseases on
other nut and shade tree crops
X. fastidiosa ssp. pauca - Citrus variegated chlorosis (CVC),
Coffee leaf scorch and olive quick decline syndrome (OQDS)
X. fastidiosa ssp. sandyi causes oleander leaf scorch (OLS) (Nerium
oleander)
08-04-2024 Dept. of PAT 32
Important disease caused by Xylella fastidiosa
(Rapicavoli et al., 2018)
33. Pierce’s disease
Almond leaf scorch
Citrus variegated chlorosis
Olive quick decline syndrome
08-04-2024 Dept. of PAT 33
34. Insect colonization (acquisition and transmission)
VECTOR
Semi-persistent
Non- circulative
Propagative
No evidence of trans-stadial or trans-ovarial transmission
08-04-2024 Dept. of PAT 34
(Backus and Morgan, 2011)
36. 08-04-2024 Dept. of PAT 36
Spiroplasma
First vector borne bacteria cultured
Spiroplasmas are fastidious organisms
Helical morphology
Cork screw motion
Lack cell wall – Triple layered membrane
Culture – Fried egg appearance
Transmitted exclusively by phloem sap-feeding
insects such as leaf hoppers
(Ammar et al., 2004)
37. There are three phytopathogenic spiroplasmas that are also
transmitted by leafhoppers (Cicadellidae)
Spiroplasma citri
Spiroplasma kunkelii
Spiroplasma phoeniceum
08-04-2024 Dept. of PAT 37
Important disease caused by Spiroplasma
(Gasparich, 2010)
40. Alteration in feeding behavior
Spiroplasma alters the feeding behavior of Circulifer tenellus:
Increase in feeding frequency
Prolongation of feeding duration
Reduction in feeding preference
08-04-2024 Dept. of PAT 40
41. 08-04-2024 Dept. of PAT 41
Infection of an insect vector with a bacterial plant
pathogen increases its propensity for dispersal
Xavier Martini, Mark Hoffmann, Monique R. Coy, Lukasz L. Stelinski, Kirsten S. PelzStelinski
Citrus Research and Education Center,,United Sates of America
To determine the Candidatus Liberibacter asiaticus manipulates behaviour of its
vector to enhance its own spread
2 NAAS Rating :-9.70
OBJECTIVE:
42. 08-04-2024 Dept. of PAT 42
Host plant: Citrus
Disease: Huanglongbing disease ( Citrus greening)
Pathogen: Candidatus Liberibacter asiaticus
Vector: Diaphorina citri (Asian citrus psyllid)
Location: Citrus Research and Education Centre, USA
Density-dependent dispersal behavior of D. citri
Dispersal behavior of D. citri depending of CLas exposure and infection
Observations
(Martini et al., 2015)
Material and methods
43. 08-04-2024 Dept. of PAT 43
Fig. 4: Density-dependent dispersal behavior of D. citri
(A) Dispersal of both male and female D. citri ,
(B) Dispersal of female D. citri ,
(C) Dispersal of male D. citri.
hd: high density (175 individuals per plant); hmd: high medium density (125 ind. p. p.); lmd: low medium
density (75 ind. p. p.); ld: low density (25 ind. p. p.)
(Martini et al., 2015)
44. 08-04-2024 Dept. of PAT 44
Fig. 5: Dispersal behavior of D. citri depending of CLas exposure and infection
(A) Male and female (B) Female (C) Male
(Martini et al., 2015)
45. 08-04-2024 Dept. of PAT 45
The Las affects the behaviour of D. citri following acquisition and the infection of D. citri
with Las increase their propensity for dispersal compare to uninfected D. citri
INFERENCE
(Martini et al., 2015)
46. Phloem inhibiting
Unable to culture
It has given
provisional
genus
Candidatus
Phytoplasma
Non flagellated
Gliding motion
Lack cell wall
Aster yellows
Tomato Big
bud
Apple
proliferation
Coconut
lethal
yellowing
Peach X
disease
Phytoplasma
08-04-2024 Dept. of PAT 46
Vector-leafhoppers, plant hoppers and psyllids
50. 08-04-2024 Dept. of PAT 50
Phytoplasma acquisition and spread
Infection status and symptom expression of the host
Infection status vector
Vector gender
51. Maize bushy stunt phytoplasma favours its spread by changing host
preference of the insect vector
08-04-2024 Dept. of PAT 51
Anderson Ramos , Mariana Bossi Esteves, Mayerli Tatiana Borbon Cortes and Joao Roberto
Spotti Lope
To determine the factors that influenced the host selection behaviour of vector
3 NAAS Rating : 9.00
Department of Entomology, College of Agriculture (ESALQ), University of Sao Paulo Brazil
OBJECTIVE:
52. 08-04-2024 Dept. of PAT 52
Host plant: Maize
Disease: maize bushy stunt phytoplasma
Pathogen: Candidatus Phytoplasma
Vector: Leafhopper (Dalbulus maidis)
Location: University of Sao Paulo, Brazil
Preference of D. Maidis for healthy vs. Asymptomatic MBSP -infected maize
leaves
Preference of D. Maidis for healthy vs. Symptomatic MBSP -infected maize
leaves
Observations
(Ramos et al., 2020)
Materials and methods
53. 08-04-2024 Dept. of PAT 53
Fig. 7: Preference of D. maidis for Healthy vs. Asymptomatic MBSP-Infected Maize Leaves
(Ramos et al., 2020)
54. 08-04-2024 Dept. of PAT 54
Fig. 8: Preference of D. maidis for Healthy vs. Symptomatic MBSP-Infected Maize Leaves
(Ramos et al., 2020)
56. 08-04-2024 Dept. of PAT 56
TENGU
First phytoplasma effector protein
identified from onion yellow phytoplasma
Inducer of witches broom symptoms
(Minato et al., 2014)
Interaction with host
57. 08-04-2024 Dept. of PAT 57
The phytoplasmal virulence factor TENGU causes plant sterility
by downregulating of the jasmonic acid and auxin pathways
Nami Minato1 , Misako Himeno1 , Ayaka Hoshi1 , Kensaku Maejima1 , Ken Komatsu2 , Yumiko Takebayashi3 ,
Hiroyuki Kasahara3 , Akira Yusa1 , Yasuyuki Yamaji1 , Kenro Oshima1 , Yuji Kamiya3 & Shigetou Namba1
Graduate School of Agricultural and Life Sciences, Japan
To alters JA and auxin syntheses in flowers, indicating that TENGU causes developmental
defects that lead to sterility through modulation of the two phytohormones
4 NAAS Rating :-10.60
OBJECTIVE:
58. 08-04-2024 Dept. of PAT 58
Host plant: Arabidopsis thaliana
Disease: Phytoplasma
Location: Tokyo University of Agriculture and Technology
A. thaliana accession Col-0 and transgenic plants were grown and maintained
under a 15 h light/9 h dark photoperiod at 230C
Inoculate Arabidopsis thaliana with onion yellows phytoplasma (OY)
Sterility in phytoplasma-infected and tengu-transgenic plants
Relative expression of ARF genes
Quantification of the endogenous hormone levels
(Martini et al., 2015)
Observations
Material and methods
59. 08-04-2024 Dept. of PAT 59
Fig. 9: Sterility in phytoplasma-infected
and tengu-transgenic plants
(Martini et al., 2015)
60. 08-04-2024 Dept. of PAT 60
Fig. 10: Phenotypes of tengu-transgenic plants
(A) Flowers and fruits exhibiting severe sterility,
and mild sterility.
B. Scanning electron micrographs of pollen grains of
wild-type and 35S::tengu
C. Relative TENGU gene expression in 35S::tengu plants
exhibiting severe sterility and mild sterility
(Martini et al., 2015)
61. 08-04-2024 Dept. of PAT 61
Fig. 11: Relative expression of ARF genes. Relative expression of ARF6 and ARF8 genes in OY-
infected and tengu-transgenic plants
(Martini et al., 2015)
62. 08-04-2024 Dept. of PAT 62
Fig. 13: Quantification of the endogenous phytohormone levels in buds (a–c).
(a), cis-JA, (b), JA-Ile, and (c), IAA. A
(Martini et al., 2015)
63. 08-04-2024 Dept. of PAT 63
The phytoplasmal effector TENGU induces plant sterility
The phytoplasmal effector TENGU induces sterility in plants by causing
developmental defects during flowering, achieved through the modulation of two
endogenous phytohormones: jasmonic acid (JA) and auxin
INFERENCE
(Martini et al., 2015)
67. The transmission efficiency of Liberibacter by their psyllid hosts appears to be
dependent on the life stage of the vector during ingestion
The transmission of CLas by D. citri adults seems to be most efficient when the
bacterium is ingested during the nymphal stages
The vertical, or Transovarial transmission of pathogens occurs
The vertical transmission of Liberibacter in psyllids occurs at a low rate of
2–6%
08-04-2024 Dept. of PAT 67
Transmission
(Mishra and Ghanim, 2022)
68. Sexual transmission of a plant pathogenic bacterium, Candidatus liberibacter
asiaticus, between conspecific insect vectors during mating
08-04-2024 Dept. of PAT 68
Rajinder S. Mann, Kirsten Pelz-Stelinski, Sara L. Hermann, Siddharth Tiwari, Lukasz L. Stelinski*
To determine the plant pathogenic bacterium is sexually transmitted during
courtship in D. citri
5 NAAS Rating : 9.70
Entomology and Nematology Department, United States of America
OBJECTIVE:
69. 08-04-2024 Dept. of PAT 69
Venereal transmission of Las between adult D. citri
Detection of Las in D. citri genetalia
Disease : Huanglongbing disease (Citrus greening)
Pathogen : Candidatus Liberibacter asiaticus
Vector : Diaphorina citri (Asian citrus psyllid)
(Mann et al., 2011)
Observations
Material and methods
70. 08-04-2024 Dept. of PAT 70
Table 2:Venereal transmission of Las between adult D. citri.
(Mann et al., 2011)
71. 08-04-2024 Dept. of PAT 71
Transmission electron microscopy (TEM) of ovaries from las-
infected females
Fig. 15: Rod shaped (A) and spherical (B) structures resembling Las in ovaries of Las-
infected female D. citri observed with transmission electron microscopy
(Mann et al., 2011)
72. 08-04-2024 Dept. of PAT 72
The plant pathogenic bacterium was transferred sexually from
male to female insects during mating
This was also confirmed with lack of transmission from females to
males, or between same sex pairs
This study marks the first report of sexual transmission of plant
pathogenic bacteria among insect vectors
INFERENCE
(Mann et al., 2011)
75. 08-04-2024 Dept. of PAT 75
Diptera
Bacterial soft rot in potatoes - seedcorn maggot (Delia platura)
Soft rot in the Brassicaceae - cabbage maggot (Delia radicium)
Bacterial soft rot in onion -onion maggot (Delia antiqua)
Southern bacterial wilt of solanaceous – Flies (Drosophila spp)
Coleoptera
Bacterial wilt of cucurbits -spotted cucumber beetle (Diabrotica undecimpunctata)
Bacterial wilt of corn – fleabeetle (Chaetocnema denticulata Illiger)
Editor's Notes
In the world of agriculture, the battle against pathogens is ongoing. Among the many threats to plant health, vector-borne pathogens pose a significant challenge.
Globally 34% of the crop produce is lost annually due to diseases, insect-pests and weeds
out of these, 12% is lost due to diseases (caused by fungi, bacteria or viruses).
In the intricate dance of nature, insects play a crucial role not just as pollinators but also as carriers of plant diseases.
ultimately these insect Vectors are the key agents that transmits plant pathogens such as virus and bacteria and cause a very sever disease in many crops.
Some of the major diseases such as tobacco mosaic virus , tomato yellow leaf curl virus and citrus greening and pierce disease of grapes.
These major disease transmitted by the insect vector so among these virus are the major group of pathogens which get transmitted through vectors but, bacteria also important group of plant pathogens that transmitted by the insect vectors but they remain unnoticed with these background information
Characteristics
Bacteria are prokaryotic single-celled microorganisms
They are non spore formers
They are small compare to fungi
capsule is a protective layer outside the cell wall
plasma membrane of bacteria, also known as the cytoplasmic membrane or cell membrane, is a vital structure that separates the interior of the bacterial cell from its external environment
Mesosomes are membrane-bound structures – Respiration, DNA Replication.
They lack membrane bound organelles such as mitochondria or plastids.
Cytoplasm containing genetic material and 70s ribosomes(Protein Synthesis) (DNA Replication and Transcription, Storage of Reserve Materials, cellular communication)
Reproduction by binary fission
Majority of the plant pathogenic bacteria are flagellated
Grow on artificial nutrient media.
Gram stain is a commonly used staining technique differentiate and classify bacteria into two main groups based on differences in the structure of their cell walls.
Gram-negative bacteria – Thin cellwall ( Plant pathogenic)
Gram-positive bacteria - Thick cellwall
Phytoplasma and spiroplasma are lack cellwall and bounded by triple layer membrane
Hemipteran insects, particularly members of the order Hemiptera, are important vectors for transmitting plant bacteria due to several reasons
Hemipteran Insects
Hemipteran insects, which include groups such as aphids, leafhoppers, and whiteflies, are particularly important vectors of plant pathogenic bacteria due to
Piercing-Sucking Mouthparts –Hemipteran insects have specialized piercing-sucking mouthparts that allow them to puncture plant tissues and feed on plant sap. During feeding, they can acquire bacterial pathogens present in the plant's vascular system
rapid transmission cycle – they have a Short Acquisition and Inoculation Periods which allows for the quick spread of bacterial diseases within plant populations
Complex Interactions - have complex interactions with both bacterial pathogens and host plants. Factors such as vector behavior, feeding preferences, and host plant defences can influence the transmission dynamics of bacterial diseases,
Stealthy transmission - It is a method of disease spread where pathogens are transmitted in a inconspicuous manner without immediate symptoms, often without immediate detection.
Salivary Secretions - saliva contains a complex mixture of compounds that can modulate plant physiology. These compounds can alter plant defense responses, suppress plant immune systems, and modify plant metabolism to create a more favourable feeding environment for the insects
Order -Hemiptera
Sub order –Sternorrhyncha
Super family
Psylloidea – psyllid – citrus greeening
Aleyrodoidea – white fly – tomato yellow leaf curl virus
Coccoidea – scales – grape leaf roll virus
Aphidoidea – aphids – papaya ringspot virus
Sub order – Auchenorrhyncha
Super family
Flugoroidea – plant hoppers – sugarcane fiji virus / Coconut lethal yellowing
Cicadoidea – sharpshooter – pierces dis of grapes
Cercopoidea – spittlebug – olive quick decline
Membracoidea – leaf hoppers – rice tungro baciliform virus / Corn stunt disease
VECTOR-BORNE BACTERIAL PLANT PATHOGENS
Bacterial vector-borne diseases cause some of the most serious crop losses worldwide.
Examples of bacterial vector-borne pathogens include members of the genera Xylella, Ca. Liberibacter, Spiroplasma, and Candidatus Phytoplasma..
Pierces dis of grapes – xylella fastidiosa – sharpshooter(Homalodisca vitripennis)
Citrus greening - Ca. Liberibacter - psyllids (Diaphorina citri)
Corn stunt disease – spiroplasma kunkelii – leafhoppers (Dalbulus maidis)
Coconut lethal yellowing - candidatus phytoplasma palmae - planthopper (Haplaxius crudus)
These are the 4 important vector-borne bacterial genera that have a major economic impact on the world..
In the year 1975 reported that an approximately 40000 coconut palms affected in Florida due to Coconut Lethal Yellowing caused by Candidatus Phytoplasma palmae.
In the year 2007 reported that an appromimate of $7.8 billion loss due to huanglongbing disease also called as citrus greening dis in florida
i,e. caused by Candidatus Liberibacter asiaticus
In the year 2013 reported that an approximately 8000ha of olive field are affected due to Olive quick decline syndrome (X. fastidiosa) in salanto peninsula (Italy).
Due to Pierce’s disease of grapevine (X. fastidiosa) an approximately $100 million loss annually in california.
Plants are imp mediators for interactions between pathogen and insects.
These three way interaction called Tripartite interaction
These interaction can influence plant susceptibility to diseases, vector behavior and plant transmission efficiency
Understanding these interaction can help for developing effective strategies for disease management
The plant pathogens and invading insect vectors mainly depends on plant vascular system.
plant vascular system act as nutrient pool which as rich source of nutrients and represents a transport pathway for colonizers.
It consists of phloem and xylem tissues
Phloem tissue act as a food conducting tissue, forming a long distance transport system throughout the plant. Because this specialized transport system contains a rich source of carbohydrates, proteins, and amino acids which is access the numerous viral and bacterial microbes colonize the phloem specifically.
xylem vessels mainly transport water and contain lower nutrient levels in comparison to the phloem.
Despite of low nutrient content of xylem, plant pathogens like xylella fastidiosa that colonize the xylem tissues.
PASSENGERS –VECTOR BORNE PATHOGENS
BACTERIA
Phylum Proteobacteria
Class alpha – G-liberibacter
Class beta --
Class gamma – G-xylella
Phylum actinobacteria
Phylum Firmicutes
Class Mollicutes – G – Spiroplasma , Phytoplasma
Class Bacilli
Class Clostridia
Bacterial Vector-Borne Diseases That Persist in Plant Vascular Tissues.
Pathogenic bacteria are delivered directly into the phloem (liberibacter, spiroplasma, and phytoplasma) or xylem (Xylella) during vector feeding.
Xylella cells move between xylem vessels through the pit membrane and exhibit differential distribution in resistant hosts.
Spiroplasmas preferentially localize near nucleated cells or in phloem parenchyma cells. Phytoplasmas attach to the sieve element membrane.
liberibacters and phytoplasmas are confined to sieve elements, move intracellularly through sieve pores, and tend to accumulate in sink tissues.
Phytoplasmas attach to the sieve element membrane.
Source - responsible for synthesising the sugars required for plant growth.
Sink - plants use the sugars for immediate use and store the rest for future metabolic needs.
bacteria-vector relationships can be categorized based on their persistence, location and replication.
non-persistent – transmission immediately after an infective feed i,e acquired within seconds to minutes of infective feed and transmitted rapidly.
semi-persistent - feeding for minutes to hours is required for acquisition and if acquisition occurs during vector immature stages, infectivity is lost after each moult
Persistent -Long feeding periods (hours to days) are required for acquisition.
LOCATION
Circulative - bacteria that circulate through the food canal and cross the midgut, hindgut and reaching the hemocoel.
Circulative bacteria can be retained for the life of the insect vector
Non-Circulative – bacteria that binds the stylet during feeding and released when the insect secrets saliva on new feeding.
REPLICATION
Non-propagative - Circulative pathogens is said to be non propagative they circulate within the insect vector without multiplying
Propagative - they can circulate and multiply within the insect vector
Mode of transmission of bacteria inside the vector
Phytoplasma, spiroplasma and liberibacter are transmitted in a persistent-propagative manner.
Phloem feeding insects acquire the bacteria (red dots) from the phloem sap of infected plants during feeding.
bacteria that circulate through the food canal and cross the midgut, hindgut and reaching the hemocoel.
They transmitted when they feed on healthy plants.
Xylella fastidiosa has a non-circulative propagative relationship with sharpshooter vectors.
These bacteria that binds the stylet during feeding and released when the insect secrets saliva on new feeding.
Plant pathogens modulate plant processes to promote attraction, colonization and dispersal of insect vectors.
Lower layer (green), Plant–pathogen interaction: Inside plants, the plant-pathogenic bacteria secrete virulence factors (effectors) into plant cells to modulate various plant cellular and physiological processes.
The majority (>80%) of those D. citri tested responded to the odors of either non-infected or Las-infected citrus plants.
More D. citri males and females were attracted to the odours from Las-infected plants than non-infected plants.
Las infected male and female psyllids were also more attracted to the odours from infected than non-infected plants.
The number of honey dew droplets produced by psyllid feeding, a surrogate measure of feeding efficiency, was significantly affected by the infection status of plants feeding exposure time.
There was no significant difference in the amount of feeding on non-infected versus infected plants after 24 h of feeding by psyllids.
psyllids fed significantly more on non-infected than on Las-infected plants after 48, 72 and 96 h, respectively
Las-infected plants were deficient in nitrogen, phosphorus, magnesium, zinc, and iron as compared with non-infected plants
Las-infected plants had higher potassium and boron contents compared with non-infected plants
MeSA act as a signalling compound in plants
It produces in plants in response to stress
It can attract beneficial insects for pollination or pest control.
our results suggest that host selection behavior of D. citri may be modified by bacterial infection of plants. which alters release of specific headspace volatiles and plant nutritional contents. initially The Las-infected plants were more attractive to D. citri adults than non-infected plants after the acquisition of the Las by psyllids healthy plants are more attractive than the Las infected
Aerobic
Gram-negative, rod-shaped
Bounded by cell wall and cell membrane.
Lack flagella
Forms a biofilm-like layer within xylem cells
Transmitted exclusively by xylem sap-feeding insects such as sharpshooters and spittlebugs
X. fastidiosa can be found in about 600 different plant species
X. fastidiosa-related diseases- marginal leaf necrosis and scorching of the leaves.
In the case of PD, X. fastidiosa can also cause desiccation of berries(Raisining)
Almond leaf scorch - Leaf Scorch, Leaf Necrosis, Premature Leaf Drop, Stunted Growth, Dieback of Branches
In the case of CVC, symptoms include foliar wilt and interveinal chlorosis on the upper surfaces of the leaves (similar to zinc deficiency) hardening of fruits.
In olive trees affected with OQDS,- marginal necrosis and defoliation, and overall tree decline, shortening of internodes
Propagate extracellularly
Xylella fastidiosa is also propagative within vectors, allowing the insects to transmit the pathogen for months after acquisition from an infected plant
There is no evidence of trans-stadial or trans-ovarial transmission.
No latent period
Biofilm formation
Cells initially attach laterally, which increases the cell surface area in contact with the insect cuticle.
Xylella fastidiosa colonizes two major regions of the foregut: the precibarium and the cibarium.
Although the cibarium is probably the reservoir for bacterial inoculum within the foregut, transient colonization of the precibarium is associated with the transmission of X. fastidiosa to plants
Spiroplasmas are fastidious organisms, which require a rich culture medium.
egg shape colony of Spiroplasma citri (c) and
streaking of Spiroplasma citri on solid media (d).
Corn stunt Spiroplasma in phloem cells. Thick section (0.4 micrometers) observed in a TEM. Magnified 75,000X.
Spiroplasma citri -citrus stubborn dis-Yellowing and Vein Clearing, Small and Misshapen Fruit
S. kunkelii –cron stunt-Stunting, chlorosis, redning of leaves, leaf rolling, uneven mathurity
Propagate extracellularly
Xylella fastidiosa is also propagative within vectors, allowing the insects to transmit the pathogen for months after acquisition from an infected plant
There is no evidence of trans-stadial or trans-ovarial transmission.
Candidatus Phytoplasma asteris - Aster Yellows Phytoplasma- yellowing of leaves, stunting, proliferation of shoots, abnormal development of flowers, and general decline in plant health
Candidatus Phytoplasma aurantifoli – witches broom dis of lime -Tomata big bud diseases -Witches' Broom, Abnormal Fruit, Yellowing of Leaves
Candidatus Phytoplasma mali – apple proliferation - flower sterility; excessive proliferation and witches broom symptoms; internode elongation; early leaf reddening, enlarged stipules, stunting; and reductions in fruit size and quality.
Lethal yellowing (LY) disease - premature dropping, e fallen nuts will have a brown or black area immediately under the calyx , blackening of new inflorescence tips, frond will turn yellow first giving a characteristic “flag” appearance.
Propagate extracellularly
Xylella fastidiosa is also propagative within vectors, allowing the insects to transmit the pathogen for months after acquisition from an infected plant
There is no evidence of trans-stadial or trans-ovarial transmission.
Phytoplasma acquisition and spread influenced by
Fig 7-Free choice assay for… pre..
In each assay 40 adults were released and check the settling prefecence with time 0 to 22 hrs
Non-bacteriliferous females, non-bacteriliferous males and bacteriliferous males had no preference for either treatment
Bacteriliferous females of D.maidis preferred to land and settle on leaves of healthy plants
In symptomatic stage of the disease, non-bacteriliferous males and females preferred to land on symptomatic leaves in the first 6 h after release
Later, there was a shift in behavior non-bacteriliferous males were equally distributed among symptomatic and healthy leaves non-bacteriliferous females showed a preference for healthy leaves after 9 h.
The bacteriliferous males were equally distributed among healthy and symptomatic leaves, showing no preference for any treatment
Bacteriliferous females did not show preference for either treatment in the first five evaluations after release, but after 9 h they clearly preferred healthy leaves
The MBSP induces shifts in host plant preference of the leafhopper vector, D. maidis, that are favorable to its primary and secondary spread and host selection behavior is influenced by maize infection status and symptom expression, as well as by the leafhopper gender and infection with MBSP.
At the early stages of the crop, bacteriliferous females prefer to land and settle on healthy leaves than on leaves of asymptomatic infected plants, a behavior that favors primary spread.
As the crop develops and infected plants become symptomatic, non-bacteriliferous males and females initially prefer to land on leaves of infected plants, but a few hours later, the females tend to move towards healthy leaves, a behavioral shift that should increase secondary spread.
Witches broom symptomes-abnormal proliferation of shoots or branches, resulting in dense clusters of growth that often resemble brooms.
a) 27-day-old wild-type (Col-0) and 35S::tengu plants.
(b–e)
(b) Inflorescence stems of Col-0
(c) onion yellows phytoplama (OY)-infected
(d) 35S::tengu plants exhibiting severe sterility
(e) mild sterility
(f–i)
(f) Flowers of Col-0
(g) OY-infected and 35S
(h) tengu plants exhibiting severe sterility
mild sterility
(j–m)
(j) Anther development in mature Col-0
(k) OY-infected
(l) 35S::tengu plants exhibiting severe sterility
(m) mild sterility
(n–q),
(n) Scanning electron micrographs of apices of gynoecia of mature Col-0
(o) OYinfected
(p) 35S::tengu plants exhibiting severe sterility
(q) mild sterility
The phytoplasmal effector TENGU induces sterility in plants by causing developmental defects during flowering, achieved through the modulation of two endogenous phytohormones: jasmonic acid (JA) and auxin.
The genus Liberibacter spp. Contains six species of phloem- limited bacteria(Haapalainen, 2014):
“Ca. Liberibacter africanus,”
“Ca. Liberibacter americanus,”
“Ca. Liberibacter asiaticus,”
“Ca. Liberibacter solanacearum,”
“Ca. Liberibacter europaeus,”and Liberibacter crescens.
“Ca. Liberibacter africanus,”“Ca. Liberibacter americanus,”and“Ca. Liberibacter asiaticus”are associated with citrus greening disease, also referred as Huanglongbing(HLB) in different regions around the globe (Gottwald, 2010).
“Ca. Liberibacter solanacearum”(D“Ca. Liberibacter psyllaurous”)is phytopathogenic to members of the Apiaceae and Solanaceae plant families.
These four species all depend on psyllid vectors for transmission and as alternative hosts (Fagenetal., 2014b; Haapalainen, 2014).
“Ca. Liberibacter europaeus”has also been associated with psyllids, but its role as a plant pathogen has not been demonstrated.
To date, only Liberibacter crescens has been cultured in vitro, but
Ca. Liberibacter africanus- African citrus greening - Fruit that remains green even when ripe, Lopsided, bitter, hard fruit with small, dark aborted seeds, Yellow shoots
Ca. Liberibacter solanacearum -zebra chip of patoto-vein greening disease in tomatoes- plant stunting, erectness of new foliage, upward leaf curling, leaf purpling and chlorosis, shortened and swollen terminal internodes resulting in leaf rosettes, enlarged nodes, axillary branches or aerial tubers and many small, misshapen fruit
Propagate extracellularly
Xylella fastidiosa is also propagative within vectors, allowing the insects to transmit the pathogen for months after acquisition from an infected plant
There is no evidence of trans-stadial or trans-ovarial transmission.
Ovaries from female psyllids that were confirmed negative for Las by qPCR were devoid of structures similar to those observed from positive females following an identical microscopic evaluation.
We've made progress in understanding how viruses spread through plants via insects, but we're still clueless about how bacteria do it. Insects like leafhoppers and psyllids can carry harmful bacteria, but we don't know a lot about how they eat or how plants respond to them carrying bacteria. These bacteria can multiply in both the insect and the plant, but they really need their hosts to survive. To solve this problem, we need more research to understand how these interactions happen and to find ways to stop these bacterial pathogens from wrecking crops.
