Disease Progress

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PENGEDALIAN PENYAKIT TUMBUHAN
Aris Mumpuni
2
Disease Progress

• Disease on plants usually starts out at a low
  level, a small number of plants affected and a
  small amount of plant tissue affected, and it
  becomes of concern to us only when its incidence
  and severity increases with time.

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Disease Progress

• When we look at some examples of plant disease
  epidemics from the published literature, we not
  only notice that the incidence or severity starts
  near zero and then increases dramatically, but we
  also can discern some distinct patterns of
  development with time.

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Disease Progress

• For example, in Phytophthora blight of pepper
  seedlings (Phytophthora capsici) and Fusarium
  kernel rot (Fusarium moniliforme) of maize,
  disease progress is roughly linear (allowing for
  some minor deviations that we can consider random
  error)

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Phytophthora blight of pepper seedlings
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Fusarium kernel rot of maize
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Disease Progress

• On the other hand, in bean rust (Uromyces
  phaseoli) and grey leaf spot of corn (Cercospora
  zeae-maydis), there is a definite upward curve
  that is, disease increases at an increasing rate,
  a curve we could call exponential.

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Bean rust
9
Grey leafspot of maize
10
Disease Progress

• Obviously plant disease cannot continue to
  increase forever, and as the level of disease
  approaches 100, the disease progress curve
  gradually flattens out. For example, in epidemics
  such as the infection of beans by Sclerotium
  rolfsii or the infection of tobacco by
  Phytophthora parasitica var. nicotianae, disease
  progress starts out looking linear but slows down
  as it approaches a maximum.

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Sclerotium rolfsii on beans
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Black shank on tobacco
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Disease Progress

• Likewise, the disease progress curves of Puccinia
  graminis subsp. graminicola on ryegrass and
  Pyrenophora teres f. sp. teres on barley appear
  exponential at first, but as time goes on and the
  incidence and severity of disease approach 100,
  the rate of disease progress gradually slows to
  zero, giving both curves a somewhat sigmoid shape
  ("S" shape).

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Black stem rust on ryegrass
15
Net blotch on barley
16

• To be sure, not all examples of disease progress
  can be as neatly categorized as these, but in
  general plant disease epidemics tend to be either
  roughly linear or exponential in the early
  stages, and they tend to level off as they
  approach some limit.

17

• The impact of plant disease and the losses that
  it causes are a function of disease progress. To
  reduce this impact, we need not eliminate the
  disease, we merely need to keep disease
  development below an acceptable level. That means
  that the progress of disease and the factors that
  influence disease progress must be understood in
  quantitative terms.

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what kinds of diseases lead to linear disease
progress and what factors affect the slope of the
line (the rate of disease progress). 2. what
kinds of diseases tend to produce exponential
disease progress curves and how we can reduce
both the starting level of disease and the rate
of epidemic development. 3. why epidemics
sometimes level off and what imposes limits to
their development.
We have to know
19
The Cyclical Nature of Plant Disease
Plant disease epidemics are cyclical phenomena,
that is, they consist of repeated cycles of
pathogen development in relation to the host.
20
The inoculum, which might consist of
fungal spores, bacterial cells, nematodes,
viruses within an aphid vector, or some other
propagules of a pathogen,
gains entry into and establishment within the
host tissues through the process of infection.
21
The pathogen develops within the host and
eventually begins to produce new inoculum, which,
in turn, can be dispersed to new susceptible
sites to initiate new infections.
22
Pathogens that produce only one cycle of
development (one infection cycle) per crop cycle
are called monocyclic, while pathogens that
produce more than one infection cycle per crop
cycle are called polycyclic.
23

• Generally in temperate climates there is only one
  crop cycle per year, so the terms "monocyclic"
  and "polycyclic" are based on the number of
  cycles per year. In tropical or subtropical
  climates, however, there can be more than one
  crop cycle per year, and it is important to
  remember that "monocyclic" and "polycyclic" are
  based on a single crop cycle. These same terms
  are used to describe the epidemics as well as the
  pathogens, so we often speak of a "monocyclic
  epidemic" or a "polycyclic epidemic".

24

Epidemic
"Change in disease intensity in ahost population
over time and space.
25

• Change often increase -- a dynamic
  process
• Disease dealing with diseases, not just
  the pathogen (or
  plant/crop)
• Host Organism infected (or
  potentially
• infected) by another
  organism
• Population a population phenomenon
• Time and space two physical dimensions
  of interest.

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• Epidemiology
• Study of epidemics.
• Science of disease in populations.
• Ecology of disease.
• Study of the spread of diseases, in space and
  time,
• with the objective to trace factors that are
  
• responsible for, or contribute to, epidemic
• occurrence.
• The science of populations of pathogens in
• populations of host plants, and the diseases
• resulting therefrom under the influence of
• the environment and human interferences.

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All plant diseases result from a three-way
interaction between the host, the pathogen and
the environment. An epidemic develops if all
three of these factors are favourable to disease
development. Therefore, disease can be
controlled by manipulating one or more of these
factors so that conditions are unsuitable for
replication, survival or infection by the
pathogen.
29
Since the beginning of agriculture, generations
of farmers have been evolving practices for
combating the various plagues suffered by our
crops. Following our discovery of the causes of
plant diseases in the early nineteenth century,
our growing understanding of the interactions of
pathogen and host has enabled us to develop a
wide array of measures for the control of
specific plant diseases.
30
From this accumulated knowledge base, we can
distill some general principles of plant disease
control that can help us address the management
of new problems on whatever crop in any
environment.
31
One such set of principles, first articulated by
H. H. Whetzel in 1929 and modified somewhat by
various authors over the years, has been widely
adopted and taught to generations of plant
pathology students around the world. These
"traditional principles", as they have come to be
known, were outlined by a committee of the US
National Academy of Sciences, 1968.
32
Avoidanceprevent disease by selecting a time of
the year or a site where there is no inoculum or
where the environment is not favorable for
infection. Exclusionprevent the introduction
of inoculum. Eradicationeliminate, destroy, or
inactivate the inoculum. Protectionprevent
infection by means of a toxicant or some other
barrier to infection. Resistanceutilize
cultivars that are resistant to or tolerant of
infection. Therapycure plants that are already
infected.
Traditional Principles of Plant Disease Control
33

• While these principles are as valid today as they
  were in 1929, in the context of modern concepts
  of plant disease management, they have some
  critical shortcomings.
• First of all, these principles are stated in
  absolute terms (e.g., "exclude", "prevent", and
  "eliminate") that imply a goal of zero disease.
  Plant disease "control" in this sense is not
  practical, and in most cases is not even
  possible. Indeed, we need not eliminate a
  disease we merely need to reduce its progress
  and keep disease development below an acceptable
  level. Instead of plant disease control, we need
  to think in terms of plant disease management.

34

• A second shortcoming is that the traditional
  principles of plant disease control do not take
  into consideration the dynamics of plant disease,
  that is, the changes in the incidence and
  severity of disease in time and space. (See
  Disease Progress.)

35

• Furthermore, considering that different diseases
  differ in their dynamics, they do not indicate
  the relative effectiveness of the various tactics
  for the control of a particular disease. They
  also fail to show how the different disease
  control measures interact in their effects on
  disease dynamics. We need some means of assessing
  quantitatively the effects of various control
  measures, singly and in combination, on the
  progress of disease.

36
Finally, the traditional principles of plant
disease control tend to emphasize tactics without
fitting them into an adequate overall strategy.

• Does this mean that we should abandon the
  traditional principles? Of course not! We merely
  have to fit them into an appropriate overall
  strategy based on epidemiological principles.

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The Epidemiological Basis of Disease Management
Plant disease epidemics can be classified into
two basic types, monocyclic and polycyclic,
depending on the number of infection cycles per
crop cycle. (See The Cyclical Nature of Plant
Disease.)
38
The early stages of a monocyclic epidemic can be
described quite well by a linear model, while the
early stages of a polycyclic epidemic can be
described with an exponential model. Since we are
concerned with keeping disease levels well below
100, there is no need to adjust the models for
approaching the upper limit, and we can use the
simple linear and exponential models to plan
strategies
39
Examining these models, we can see that in both
there are three ways in which we can reduce x at
any point in the epidemic

1. Reduce the initial inoculum (Q in the monocyclic
   model and xo in the polycyclic model). (Actually
   xo is the initial incidence of disease, which is
   proportional to the initial inoculum.)
2. Reduce the rate of infection (R in the monocyclic
   model and r in the polycyclic model)
3. Reduce the duration of the epidemic (the time, t,
   at the end of the epidemic)

40
These can be used as three major strategies for
managing plant disease epidemics, and we can
organize our plant disease control tactics under
one or more of these overall strategies.
Furthermore, by means of the model we can
assess the quantitative impact of each strategy,
not only by itself, but in its interaction with
others.
41
The monocyclic model
It is clear from the above model of a monocyclic
epidemic that Q, R, and t have equal weight in
their effect on x. A reduction in the initial
inoculum or the rate of infection will result in
a reduction in the level of disease by the same
proportion at any time, t, throughout the
epidemic. If t can be reduced (for example, by
shortening the season), disease will be reduced
proportionately.
42
The polycyclic model

• If r is very high, the apparent
• effect of reducing xo is to delay
• the epidemic.
• If r is very high, xo must be reduced to very low
  levels to have a significant effect on the
  epidemic.
• Reducing r has a relatively greater effect on the
  epidemic than reducing xo.
• Reducing xo makes good strategic sense only if r
  is low or if r is also being reduced.

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The Traditional Principles Revisited

• To make the conceptual leap from disease control
  to disease management, the traditional principles
  can be modified by fitting them as tactics within
  each of the three major disease management
  strategies and by slightly changing the wording
  to reflect the quantitative impact of the action
  rather than an absolute effect

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PRINSIP PENGELOLAAN PENYAKIT TUMBUHAN

• Pada prinsipnya, untuk mengelola penyakit
  tumbuhan ada strategi dan ada taktik yang dapat
  digunakan.
• Taktik dipakai untuk mencapai tujuan berdasar
  strategi yang dicanangkan.
• Secara umum, ada tiga strategi yang dapat
  dilakukan untuk pengendalian penyakit tumbuhan
  yaitu
• (1) strategi untuk mengurangi inokulum awal,
• (2) strategi untuk mengurangi laju infeksi, dan
• (3) strategi untuk mengurangi lamanya epidemi.
• Sedangkan taktik pada prinsipnya ada enam, yaitu
  avoidan, ekslusi, eradikasi, proteksi,
  resistensi, dan terapi.

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Tactics for the Reduction of Initial Inoculum

• Avoidancereduce the level of disease by
  selecting a season or a site where the amount of
  inoculum is low or where the environment is
  unfavorable for infection
• Exclusionreduce the amount of initial inoculum
  introduced from outside sources
• Eradicationreduce the production of initial
  inoculum by destroying or inactivating the
  sources of initial inoculum (sanitation, removal
  of reservoirs of inoculum, removal of alternate
  hosts, etc.)
• Protectionreduce the level of initial infection
  by means of a toxicant or other barrier to
  infection
• Resistanceuse cultivars that are resistant to
  infection, particularly the initial infection
• Therapyuse thermotherapy, chemotherapy and/or
  meristem culture to produce certified seed or
  vegetative planting stock

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Tactics for the Reduction of the Infection Rate

• Avoidancereduce the rate of production of
  inoculum, the rate of infection, or the rate of
  development of the pathogen by selecting a season
  or a site where the environment is not favorable
• Exclusionreduce the introduction of inoculum
  from external sources during the course of the
  epidemic
• Eradicationreduce the rate of inoculum
  production during the course of the epidemic by
  destroying or inactivating the sources of
  inoculum (roguing)
• Protectionreduce the rate of infection by means
  of a toxicant or some other barrier to infection
• Resistanceplant cultivars that can reduce the
  rate of inoculum production, the rate of
  infection, or the rate of pathogen development
• Therapycure the plants that are already infected
  or reduce their production of inoculum

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Tactics for the Reduction of the Duration of the
Epidemic

• Avoidanceplant early maturing cultivars or plant
  at a time that favors rapid maturation of the
  crop
• Exclusiondelay the introduction of inoculum from
  external sources by means of plant quarantine

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Peranan pengendalian penyakit tumbuhan

• Ditujukan untuk mencegah atau mengurangi
  terjadinya penyakit sehingga tanaman dapat
  memberikan hasil yang menguntungkan.
• Usaha ini biasanya ditujukan terhadap tanaman
  sebagai populasi dan tidak terhadap tanaman
  sebagai individu.
• Kebanyakan dari usaha pengendalian penyakit
  memerlukan perpaduan dari berbagai cara.

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Cara pendekatan

• pendekatan terhadap tanaman
• pendekatan yang ditujukan terhadap penyebab
  penyakit tertentu
• Terintegrasi ke dalam
• METODA PENGENDALIAN

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Penghindaran patogen

• Pemilihan daerah pertanian.
• Pemilihan waktu tanam.
• Penggunaan benih yang bebas penyakit.

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Eksklusi patogen

• Perawatan bahan tanaman.
• Karantina tumbuhan.
• Pembasmian serangga vektor.

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Eradikasi patogen

• Pergiliran tanam.
• Membuang atau menghancurkan tanaman atau bagian
  tanaman yang terserang.
• Perlakuan tanah.

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Perlindungan tanaman

• Pengendalian serangga pembawa patogen.
• Mengubah keadaan lingkungan.
• Mengubah keadaan zat hara.

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Mengembangkan tanaman yang resisten

• Resistensi fisiologis
• Resistensi mekanis
• Resistensi fungsional
• Resistensi oleh Khemoterapi

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a. Resistensi fisiologis yang biasanya didasarkan
kepada adanya zat di dalam protoplasma yang
menghambat infeksi patogen dan perkembangannya
lebih lanjut di dalam tanaman. b. Resistensi
mekanis yang berhubungan dengan struktur atau
morfologi dari bagian-bagian tanaman tertentu
meliputi sifat karakteristik yang dipunyai oleh
tanaman yang menyulitkan patogen mengadakan
kontak secara langsung dengan bagian yang akan
diinfeksinya seperti adanya lapisan kutikula atau
lapisan gabus yang tebal.
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c. Resistensi fungsional yang berhubungan dengan
waktu penutupan stomata. d. Resistensi oleh
Khemoterapi dimana terdapat kemungkinan mengubah
ketahanan terhadap patogen yang terdapat dalam
protoplasma dengan pemberian senyawa kimia pada
tanaman. Pada umumnya cara tersebut memperlambat
atau mengurangi timbulnya penyakit.
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Terapi yang diberikan kepada tanaman sakit

• Khemoterapi.
• Perlakuan panas.
• Menghilangkan bagian tanaman yang kena infeksi.

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Metoda pengendalian

• Regulatory
• Cultural
• Biological
• Physical
• Chemical

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Regulatory control

• Menangkal suatu patogen dari suatu inang atau
  dari suatu area geografis tertentu

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Regulatory Control
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Cultural control

• Mengusahakan tanaman terhindar dari kontak dengan
  patogen, mengusahakan kondisi lingkungan tidak
  menguntungkan bagi patogen dan melenyapkan atau
  mengurangi jumlah patogen pada suatu tanaman,
  lahan atau wilayah

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Biological control

• Meningkatkan resistensi inang atau menciptakan
  kondisi yang menguntungkan bagi mikroorganisma
  antagonistik bagi patogen

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Physical and chemical control

• Melindungi tanaman dari inokulum patogen yang
  sudah ada atau akan ada, atau mengobati suatu
  infeksi yang sudah/sedang berlangsung

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Regulatory control
Biological control
Cultural control
Physical and chemical control
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pestisida
PENGENDALIAN PENYAKIT TUMBUHAN SECARA KIMIAWI
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PERATURAN PEMERINTAH NO. 7 TAHUN 1973

• Untuk melindungi keselamatan manusia dan
  sumber-sumber kekayaan alam khususnya kekayaan
  alam hayati, dan supaya pestisida dapat digunakan
  efektif, maka peredaran, penyimpanan dan
  penggunaan pestisida diatur dengan Peraturan
  Pemerintah No. 7 Tahun 1973. Dalam peraturan
  tersebut antara lain ditentukan bahwa

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• tiap pestisida harus didaftarkan kepada Menteri
  Pertanian melalui Komisi Pestisida untuk
  dimintakan izin penggunaannya
• hanya pestisida yang penggunaannya terdaftar dan
  atau diizinkan oleh Menteri Pertanian boleh
  disimpan, diedarkan dan digunakan
• pestisida yang penggunaannya terdaftar dan atau
  diizinkan oleh Menteri Pertanian hanya boleh
  disimpan, diedarkan dan digunakan menurut
  ketentuan-ketentuan yang ditetapkan dalam izin
  pestisida itu
• tiap pestisida harus diberi label dalam bahasa
  Indonesia yang berisi keterangan-keterangan yang
  dimaksud dalam surat Keputusan Menteri Pertanian
  No. 429/ Kpts/Mm/1/1973 dan sesuai dengan
  ketentuan-ketentuan yang ditetapkan dalam
  pendaftaran dan izin masing-masing pestisida.

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What is a fungicide?

• Fungicides are pesticides that specifically kill
  fungi or inhibit fungal development
• About 40 different classes of fungicides used for
  plant protection
• Classes are based on target site and biochemical
  mode of action

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Multi-site
Site-specific
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Systemicity
Non-systemic
Systemic

• Do not penetrate into plant
• Redistribute on plant surfaces
• Multi-site inhibitors
• Kills spores/inhibits germination
• Protectant only
• Broad spectrum

• Penetrate into plant
• Redistribute on within plants
• Single-site inhibitors
• Inhibits spore germination and or mycelial growth
• Protectant and curative
• Selective

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Non-systemics

• Mimimal redistribution from the point of
  deposition
• Works by contact with the fungus
• Adequate coverage is essential
• On the cuticle
• Redistributed washed off by water
• EBDCs, Chlorothalanil, etc.

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Systemics

• Local Systemic
• Local redistribution from the point of deposition
• On the cuticle
• Through the leaf (translaminar)
• Extent is variable

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Systemics

• Limited systemic (acropetal penetrant)
• Good movement from the point of application
• Through tissues
• Inside the vasculature
• Bulk movement
• DMIs, Phenylamides

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Systemics

• True Systemics (Basipetal penetrant)
• Only one fungcide
• Fosetyl-Al
• Moves through plant
• Down into roots
• Good against soil-borne oomycetes

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Single Site v. Multi-siteSystemic v. non-Systemic
Non-systemic/Multi-Site
Systemic/Single Site

• Protectant only
• Can wash off
• Shorter application intervals
• Broad spectrum
• Low Risk of Resistance

• Protectant and curative
• Less prone to washing off
• Longer application intervals
• Selective
• High Risk of Resistance

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Biological mode of actionAksi Fungisida dapat
diekspresikan melalui salah satu dari dua cara
ekspresi fisik
Pola Laku Kimiawi pada Pengendalian Penyakit
Tanaman

• Penghambatan perkecambahan
• spora.
• Penghambatan pertmbuhan jamur.

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Physiological mode of action Apa yang terjadi
pada tingkatan seluler shg dapat menyebabkan
pengaruh visibel pada perkecambahan spora dan
pertumbuhan jamur?
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Mengapa perlu mengenali pola laku fungisida
secara fisiologis?

• For resistance management
• and preservation of fungicide effectiveness.

Untreated
Treated
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The physiological mode of action

• Fungicides are metabolic inhibitors and their
  modes of action can be classified into four broad
  groups.
• Inhibitors of electron transport chain.
• Inhibitors of enzymes.
• Inhibitors of nucleic acid metabolism and protein
  synthesis.
• Inhibitors of sterol synthesis.

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A typical cell and cell components

• Electron transport chain
• Enzymes
• Nucleic acid metabolism
• and protein synthesis
• Sterol synthesis

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Inhibition of electron transport
chain(Respiration in mitochondria)

• Sulfur
• Disrupts electron transport along the cytochromes
• Strobilurins (azoxystrobin, kresoxim-methyl,
  pyraclostrobin, trifloxystrobin)
• Inhibit mitochondrial respiration, blocking the
  cytochrome bc1 complex.

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Discovery and Synthesis from Natural Products
Myxococcus fulvus
Strobilurus tenacellus
Oudemansiella mucida
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Synthesis from Natural Products
Oudemansin A
Strobilurin A
Enol ether stilbene
Oxime Ether Group
Enol Ether Group
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Inhibition of enzymes

• Copper
• Nonspecific denaturation of proteins and enzymes.
• Dithiocarbamates (maneb, manzate, dithane, etc)
• Inactivate SH groups in amino acids, proteins
  and enzymes.
• Substituted aromatics (chlorothalonil, PCNB)
• Inactivate amino acids, proteins and enzymes by
  combining with amino and thiol groups.
• Organophosphonate (fosetyl-Al)
• Disrupts amino acid metabolism.

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Inhibition of nucleic acid metabolism and protein
synthesis

• Benzimidazoles (thiophanate-methyl)
• Inhibit DNA synthesis (nuclear division).
• Phenylamides (mefenoxam)
• Inhibits RNA synthesis.
• Dicarboximides (iprodione, vinclozolin)
• Inhibits DNA and RNA synthesis, cell division and
  cellular metabolism.

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Inhibition of sterol synthesis (Inhibit
demethylation of ergosterol)

• Ergosterol is the major sterol in most fungi.
• It is essential for membrane structure and
  function.

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Sterol inhibiting fungicides

• Imidazoles (imazalil)
• Triazoles (propiconazole, myclobutanil,
  tebuconazole, triflumazole)
• Morpholines (dimethomorph)
• Inhibits sterol production at different site than
  imidazoles and triazoles. Affects cell wall
  production.

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Biological control of plant pathogens

• Christine Roath

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Overview

• What is biological control, what are the benefits
  to its use
• Mechanism of biological control
• Requirements of successful biocontrol
• Working example of biocontrol

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What is biological control?

• First coined by Harry Smith in relation to the
  biological control of insects
• Suppression of insect populations by native or
  introduced enemies
• Generic terms
• A population-leveling process in which the
  population of one species lowers the number of
  another

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Why use biological control?

• WHEN
• Biological control agents are
• Expensive
• Labor intensive
• Host specific
• WHILE
• Chemical pesticides are
• cost-effective
• easy to apply
• Broad spectrum

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Why use biological control?

• WILL
• Chemical pesticides
• Implicated in ecological, environmental, and
  human health problems
• Require yearly treatments
• Broad spectrum
• Toxic to both beneficial and pathogenic species
• BUT
• Biological control agents
• Non-toxic to human
• Not a water contaminant concern
• Once colonized may last for years
• Host specific
• Only effect one or few species

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Mechanisms of biological control of plant
pathogens

• Antibiosis inhibition of one organism by
  another as a result of diffusion of an antibiotic
• Antibiotic production common in soil-dwelling
  bacteria and fungi
• Example zwittermicin A production by B. cereus
  against Phytophthora root rot in alfalfa

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Mechanisms of biological control of plant
pathogens

• Nutrient competition competition between
  microorganisms for carbon, nitrogen, O2, iron,
  and other nutrients
• Most common way organisms limit growth of others
• Example
• P. fluorescens, VITCUS, prevents bacterial blotch
  by competing with P. tolaasii

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Mechanisms of biological control of plant
pathogens

• Destructive mycoparasitism the parasitism of
  one fungus by another
• Direct contact
• Cell wall degrading enzymes
• Some produce antibiotics
• Example
• Trichoderma harzianum, BioTrek, used as seed
  treatment against pathogenic fungus

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Requirements of successful biocontrol

• Highly effective biocontrol strain must be
  obtained or produced
• Be able to compete and persist
• Be able to colonize and proliferate
• Be non-pathogenic to host plant and environment

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Requirements of successful biocontrol

• Inexpensive production and formulation of agent
  must be developed
• Production must result in biomass with excellent
  shelf live
• To be successful as agricultural agent must be
• Inexpensive
• Able to produce in large quantities
• Maintain viability

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Requirements of successful biocontrol

• Delivery and application must permit full
  expression of the agent
• Must ensure agents will grow and achieve their
  purpose

Coiling of Trichoderma around a pathogen. (Plant
Biocontrol by Trichoderma spp. Ilan Chet, Ada
Viterbo and Yariv Brotman)
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Plant pathogen control by Trichoderma spp.

• Trichoderma spp. are present in nearly all
  agricultural soils
• Antifungal abilities have been known since 1930s
• Mycoparasitism
• Nutrient competition
• Agriculturally used as biocontrol agent and as a
  plant growth promoter

                                                                                                                                                                                                       
http//www.ars.usda.gov/is/pr/2002/021231.trichode
rma.jpg
101
Plant pathogen control by Trichoderma spp.

• How is it applied?
• Favored by presence of high levels of plant roots
• Some are highly rhizosphere competent
• Capable of colonizing the expanding root surface
• Can be used as soil or seed treatment

http//www.nysaes.cornell.edu/ent/biocontrol/patho
gens/images/trichoderma3.jpg
102
Plant pathogen control by Trichoderma spp.

• Action against pathogenic fungi

• Attachment to the host hyphae by coiling
• Lectin-carbohydrate interaction

(Hubbard et al., 1983. Phytopathology
73655-659).
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Plant pathogen control by Trichoderma spp.

• Action against pathogenic fungi

• 2. Penetrate the host cell walls by secreting
  lytic enzymes
• Chitinases
• Proteases
• Glucanases

(Ilan Chet, Hebrew University of Jerusalem).
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Plant pathogen control by Trichoderma spp.

• Some strains colonize the root with mycoparasitic
  properties
• Penetrate the root tissue
• Induce metabolic changes which induce resistance
• Accumulation of antimicrobial compounds

105
Plant pathogen control by Trichoderma spp.

• Commercial availability
• T-22
• Seed coating, seed pieces, transplant starter
• Protects roots from diseases caused by Pythium,
  Rhizoctonia and Fusarium
• Interacts with the Rhizosphere, near the root
  hairs and increases the available form of
  nutrients needed by plants.

106
Plant pathogen control by Trichoderma spp.

• Future developments
• Transgenes
• Biocontrol microbes contain a large number of
  genes which allow biocontrol to occur
• Cloned several genes from Trichoderma as
  transgenes
• Produce crops which are resistant to plant
  diseases
• Currently not commercially available

107
SUSTAINABLE MANAGEMENT OF SOIL-BORNE PLANT
DISEASES
108
a reduction of biodiversity of soil organisms
Soil-borne diseases
Restoring beneficial organisms that attack,
repel, or otherwise antagonize disease-causing
pathogens will render a soil disease-suppressive
Plants growing in disease-suppressive soil resist
diseases much better than in soils low in
biological diversity.
Beneficial organisms can be added directly, or
the soil environment can be made more favorable
for them through use of compost and other organic
amendments.
Compost quality determines its effectiveness at
suppressing soil-borne plant diseases.
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Why Disease?
Plant diseases result when a susceptible host and
a disease-causing pathogen meet in a favorable
environment
If any one of these three conditions were not
met, there would be no disease.
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• Many intervention practices (fungicides, methyl
  bromide fumigants, etc.) focus on taking out the
  pathogen after its effects become apparent.
• How to emphasizes on making the environment less
  disease-favorable and the host plant less
  susceptible.

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