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.
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.
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)
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.
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.
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).
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.
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.
1.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 :
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.
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.
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.
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.
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".
Epidemic: "Change in disease intensity in a host population over time and space.“
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.
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.
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.
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.
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.
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.
Avoidance—prevent 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. Exclusion—prevent the introduction of inoculum. Eradication—eliminate, destroy, or inactivate the inoculum. Protection—prevent infection by means of a toxicant or some other barrier to infection. Resistance—utilize cultivars that are resistant to or tolerant of infection. Therapy—cure plants that are already infected. Traditional Principles of Plant Disease Control
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.
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.)
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.
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.
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.)
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:
1.Reduce the initial inoculum (Q in the monocyclic model and x o in the polycyclic model). (Actually x o 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) 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:
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.
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. The monocyclic model
The polycyclic model If r is very high, the apparent effect of reducing x o is to delay the epidemic. If r is very high, x o 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 x o. Reducing x o makes good strategic sense only if r is low or if r is also being reduced.
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:
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.
Tactics for the Reduction of Initial Inoculum Avoidance—reduce 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 Exclusion—reduce the amount of initial inoculum introduced from outside sources Eradication—reduce 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.) Protection—reduce the level of initial infection by means of a toxicant or other barrier to infection Resistance—use cultivars that are resistant to infection, particularly the initial infection Therapy—use thermotherapy, chemotherapy and/or meristem culture to produce certified seed or vegetative planting stock
Tactics for the Reduction of the Infection Rate Avoidance—reduce 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 Exclusion—reduce the introduction of inoculum from external sources during the course of the epidemic Eradication—reduce the rate of inoculum production during the course of the epidemic by destroying or inactivating the sources of inoculum (roguing) Protection—reduce the rate of infection by means of a toxicant or some other barrier to infection Resistance—plant cultivars that can reduce the rate of inoculum production, the rate of infection, or the rate of pathogen development Therapy—cure the plants that are already infected or reduce their production of inoculum
Tactics for the Reduction of the Duration of the Epidemic Avoidance—plant early maturing cultivars or plant at a time that favors rapid maturation of the crop Exclusion—delay the introduction of inoculum from external sources by means of plant quarantine
MENGURANGI LAJU INFEKSI MENGURANGI LAMANYA EPIDEMI MENGURANGI INOKULUM AWAL PENGENDALIAN PENYAKIT TUMBUHAN EKSLUSI AVOIDAN STRATEGI Waktu tanam, lahan, lingkungan yg tak cocok untuk patogen Mengurangi jumlah inokulum awal yang berasal dari luar lahan Sanitasi, buang sumber inokulum, musnahkan inang antara, dsb. Aplikasi fungisida, atau buat penghalang infeksi pd tanaman Kultivar yang tahan terhadap infeksi inokulum awal Terapi panas, kimia, benih / bag. tan. vegetativ bebas penyakit EKSLUSI TERAPI ERADIKASI RESISTEN PROTEKSI TAKTIK AVOIDAN Laju dikurangi dg waktu tanam, lahan, lingkungan yg tak cocok Kurangi masuknya inokulum selama terjadinya epidemi Tebang, pangkas, musnahkan inokulum saat terjadinya epidemi Kurangi laju infeksi dengan fungisida atau penghalang lain Kultivar yang mengurangi laju in- feksi/perkemb.patogen/inokulum Sembuhkan tanaman yang telah terinfeksi EKSLUSI TERAPI ERADIKASI RESISTEN PROTEKSI AVOIDAN Tanaman cepat dewasa agar terhindar dari infeksi Hambat introduksi inokulum dari luar dengan karantina
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.
Cara pendekatan pendekatan terhadap tanaman pendekatan yang ditujukan terhadap penyebab penyakit tertentu Terintegrasi ke dalam METODA PENGENDALIAN
Penghindaran patogen Pemilihan daerah pertanian. Pemilihan waktu tanam. Penggunaan benih yang bebas penyakit.
Eksklusi patogen Perawatan bahan tanaman. Karantina tumbuhan. Pembasmian serangga vektor.
Eradikasi patogen Pergiliran tanam. Membuang atau menghancurkan tanaman atau bagian tanaman yang terserang. Perlakuan tanah.
Perlindungan tanaman Pengendalian serangga pembawa patogen. Mengubah keadaan lingkungan. Mengubah keadaan zat hara.
Mengembangkan tanaman yang resisten Resistensi fisiologis Resistensi mekanis Resistensi fungsional Resistensi oleh Khemoterapi
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.
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.
Terapi yang diberikan kepada tanaman sakit Khemoterapi. Perlakuan panas. Menghilangkan bagian tanaman yang kena infeksi.
Metoda pengendalian 1.Regulatory 2.Cultural 3.Biological 4.Physical 5.Chemical
Regulatory control Menangkal suatu patogen dari suatu inang atau dari suatu area geografis tertentu
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
Biological control Meningkatkan resistensi inang atau menciptakan kondisi yang menguntungkan bagi mikroorganisma antagonistik bagi patogen
Physical and chemical control Melindungi tanaman dari inokulum patogen yang sudah ada atau akan ada, atau mengobati suatu infeksi yang sudah/sedang berlangsung
MENGURANGI LAJU INFEKSI MENGURANGI LAMANYA EPIDEMI MENGURANGI INOKULUM AWAL PENGENDALIAN PENYAKIT TUMBUHAN EKSLUSI AVOIDAN STRATEGI EKSLUSI TERAPI ERADIKASI RESISTEN PROTEKSI TAKTIK AVOIDAN EKSLUSI TERAPI ERADIKASI RESISTEN PROTEKSI AVOIDAN Regulatory control Cultural control Biological control Physical and chemical control
PENGENDALIAN PENYAKIT TUMBUHAN SECARA KIMIAWI pestisida
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:
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.
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
Systemicity 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 Non-systemicSystemic
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.
Systemics Local Systemic –Local redistribution from the point of deposition –On the cuticle –Through the leaf (translaminar) –Extent is variable
Systemics Limited systemic (acropetal penetrant) –Good movement from the point of application –Through tissues –Inside the vasculature –Bulk movement –DMIs, Phenylamides
Systemics True Systemics (Basipetal penetrant) –Only one fungcide –Fosetyl-Al –Moves through plant –Down into roots –Good against soil- borne oomycetes
Single Site v. Multi-site Systemic v. non-Systemic 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 Non-systemic/Multi-SiteSystemic/Single Site
Biological mode of action Aksi Fungisida dapat diekspresikan melalui salah satu dari dua cara ekspresi fisik Penghambatan perkecambahan spora. Penghambatan pertmbuhan jamur. Pola Laku Kimiawi pada Pengendalian Penyakit Tanaman
Physiological mode of action Apa yang terjadi pada tingkatan seluler shg dapat menyebabkan pengaruh visibel pada perkecambahan spora dan pertumbuhan jamur?
Mengapa perlu mengenali pola laku fungisida secara fisiologis? For resistance management and preservation of fungicide effectiveness. Untreated Treated
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.
A typical cell and cell components – Electron transport chain – Enzymes – Nucleic acid metabolism and protein synthesis – Sterol synthesis
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 bc 1 complex.
Discovery and Synthesis from Natural Products Strobilurus tenacellus Oudemansiella mucida Myxococcus fulvus
Oudemansin A O O O O Strobilurin A O O O Enol ether stilbene O O O Enol Ether Group CN O O N N O O O Oxime Ether Group O O O N O Synthesis from Natural Products
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.
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.
Inhibition of sterol synthesis (Inhibit demethylation of ergosterol) Ergosterol is the major sterol in most fungi. It is essential for membrane structure and function.
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.
Biological control of plant pathogens Christine Roath
Overview What is biological control, what are the benefits to its use Mechanism of biological control Requirements of successful biocontrol Working example of biocontrol
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
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
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
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
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
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
Requirements of successful biocontrol 1.Highly effective biocontrol strain must be obtained or produced a.Be able to compete and persist b.Be able to colonize and proliferate c.Be non-pathogenic to host plant and environment
Requirements of successful biocontrol 2.Inexpensive production and formulation of agent must be developed a.Production must result in biomass with excellent shelf live b.To be successful as agricultural agent must be i.Inexpensive ii.Able to produce in large quantities iii.Maintain viability
Requirements of successful biocontrol 3.Delivery and application must permit full expression of the agent a.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)
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.trichoderma.jpg
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/biocontro l/pathogens/images/trichoderma3.jpg
Plant pathogen control by Trichoderma spp. Action against pathogenic fungi 1.Attachment to the host hyphae by coiling a.Lectin-carbohydrate interaction (Hubbard et al., 1983. Phytopathology 73:655-659).
Plant pathogen control by Trichoderma spp. Action against pathogenic fungi 2. Penetrate the host cell walls by secreting lytic enzymes a.Chitinases b.Proteases c.Glucanases (Ilan Chet, Hebrew University of Jerusalem).
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
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.
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
SUSTAINABLE MANAGEMENT OF SOIL-BORNE PLANT DISEASES
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.
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.
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.