Presentation on theme: "Diseases. Apple Scab- Venturia inaequalis One of the Major Diseases in Apples."— Presentation transcript:
Apple Scab- Venturia inaequalis One of the Major Diseases in Apples
Apple Scab- Venturia inaequalis Pest Monitoring Monitoring the weather An apple scab forecasting model. Visual monitoring in autumn assessment of scab on fruit for the following year prediction.
Apple Scab- Monitoring, Forecasting Model Apple scab outbreaks can be predicted based on temperature and moisture conditions. The table below, derived from research by Mills and La Plante, gives hours needed at various temperatures under constantly wet conditions for primary spores (ascospores) to cause infection in spring. An electronic apple scab forecasting unit
A Chart for Predicting the Occurrence of Apple Scab( Mills, N.Z ) Days until lesions appear Heavy infection Moderate infection Light infection Average temperature (°C) Hours of wetness required for infection during spring
Prevention Varieties incorporating scab resistance Sanitation Pruning and tree training Leaf raking and urea Control Fungicides - cover spraying Apple Scab - Implementation
Most currently available resistant varieties have a single gene that governs apple scab resistance. Apple scab fungus easily overcomes the resistance (similar to fungicide resistance). Failure of resistant varieties has already occurred at some locations in Europe and the U.S. Apple Scab – Prevention, R esistant Varieties
Apple Scab Control- Fungicides Two Groups of Fungicides; Protectant Curative Resistance Among all groups resistance had appeared in different degrees.
Apple Scab Control- Fungicides Protectant Fungicides Advantages Disadvantages Diseases are very slow to develop resistance to protectants. Effective against a range of diseases. On average, less expensive than curatives. Superficial and can be washed off if rain falls within the ‘ ‑ rain fast’ period. Kill many fungi, including beneficial micro-organisms
Apple Scab Control- Fungicides Curative Fungicides Advantages Disadvantages Less harmful than protectant fungicides to non-target fungi, including beneficial species. Provide longer crop protection during prolonged wet weather. Fungal pathogens will become resistant following repeated application.
Inspire (difenoconazole) Nova (myclobutanil) Nustar (flusilazole) Sovran (kresoxim-methyl) Flint (trifloxystrobin) Pristine (boscalid + pyraclostrobin) Vangard (cyprodinil) Scala (pyrimethanil) Senator (thiophanate-methyl) Equal (dodine) Apple Scab Control- Fungicides Curative - Fungicides
Fungicide Resistance Management The fungicides: Nova, Nustar, Inspire, Sovran, Flint, Pristine, Vangard and Scala are at risk for resistance. Note, Nova, Nustar and Inspire belong to the same class (sterol inhibitors). Sovran, Flint and Pristine belong to the same class (strobilurins) Vangard and Scala belong to the same class (anilinopyrimidine).
One of the Major Diseases in Banana Panama Disease, Caused by Fusarium oxysporum
Fusarium oxysporum Strains of F. oxysporum have been studied for more than 100 years. The host rangeof these fungi is extremely broad, and includes animals, ranging from arthropods to humans, as well as plants. Collectively, plant pathogenic F. oxysporum strains have a broad host range, but usually,only individual isolates cause disease on a narrow range of plant species.
Panama Disease, Fusarium Wilt The pathogen is resistant to fungicide and cannot be controlled chemically. Panama disease is undoubtedly one of the most destructive plant diseases in modern times It can spread with soil and water movement, and with movement of infected planting material.
Symptoms It is a soil pathogen which infects the root system and goes on to colonise the plant through the vascular system – hyphae of the fungus can even reach the leaves.
Panama disease is considered to be one of the most destructive diseases of banana. It can spread with soil and water movement, and with movement of infected planting material. It is a soil pathogen which infects the root system and goes on to colonise the plant through the vascular system – hyphae of the fungus can even reach the leaves. The disease cannot be controlled or cured other than by soil treatments, which unfortunately have such a detrimental effects on the environment that they are prohibited almost everywhere.
Panama disease World Spread the disease was first reported in Australia in In the 1950s, Panama disease wiped out the Gros Michel banana, the dominant cultivar of bananas, inflicting enormous costs and forcing producers to switch to other, disease-resistant cultivars. Panama disease is now found in all banana-producing regions except islands in the South Pacific, the Mediterranean, Melanesia, and Somalia.
Geographical distribution of Panama disease
Resistant Varieties The export banana industry was only saved by the introduction of the cultivar ‘Cavendish’ (AAA genome), which was resistant to F. oxysporum f. sp. Cubense Outbreaks of the disease on ‘Cavendish’ in Australia, the Canary Islands, South Africa (Ploetz, 1990) and Southern Asia (O’Donnell et al., 1998) are threatening the continued use of this cultivar. Cavendish lacks genetic diversity, which makes it vulnerable to diseases.
Since the 1990s a new strain of the Fusarium fungus – the so- called Tropical Race (TR) 4 – has occurred and spread, destroying ten thousands of hectares of plantations of Cavendish bananas. Farmers in China, Indonesia, Malaysia, the Philippines and Australia are threatened in their business and livelihoods.
Using IPM methods for the control of Fusarium oxysporum f. sp. cubense race 4 = FOC
Managed Application One control method is to improve soil conditions because F. oxysporum spreads faster through soils that have high moisture and bad drainage
Intercropping Intercropping and rotating banana with Chinese chive can control Panama disease and increase cropland biodiversity. Antifungal volatiles released from Chinese chive help control Panama disease in banana Zhang H. et al. J.Chem. Ecol 2013 ole of plant volatiles.
Biological Control Agents Pseudomonas fluorescens Bacillus subtilis Trichoderma
Pseudomonas fluorescens Pseudomonas fluorescens is one of the major fungal biocontrol agents found in the soil, water and the rhizosphere of various crop systems. It is an obligate aeroal, but certain strains are capable of using nitrate instead of oxygen. P. fluorescens strains which present biocontrol properties, protect the roots of some plant species against parasitic fungi such as Fusarium or Pythium, as well as some phytophagous nematodes.
P. fluorescens Theories how the plant growth-promoting properties of P. fluorescens are achieved: 1.The bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen. 2.The bacteria might outcompete other (pathogenic) soil microbes, giving a competitive advantage at scavenging for iron. 3. The bacteria might produce compounds antagonistic to other soil microbes, such as phenazin, antibiotics type.
Pseudomonas fluorescens Induced Enzymological Changes in Banana Roots T. Saravanan et al. 2004, Plant Pathology Journal Pseudomonas fluorescens isolated from banana rhizosphere reduced the vascular discolouration associated with Fusarium wilt disease and induced the accumulation of resistance associated enzymes in roots. P. fluorescens treatment and challenge inoculation with the pathogen stimulated more enzymes accumulation in roots. Peroxidase (PO) is a multipurpose enzyme that catalyses the condensation of phenolics into lignin and play specific role in the hypersensitive containment of the pathogen.
Bacillus subtilis A member of the genus Bacillus. B. subtilis has the ability to form a protective endosphore, allowing the organism to tolerate extreme environmental conditions. Although this species is commonly found in soil, more evidence suggests that B. subtilis is a normal gut commensal in humans.
Trichoderma Trichoderma is a genus of fungi that is present in all soils, where they are the most prevalent cultivable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts. Several Trichoderma species have the ability to form mutualistic endophytic relationships with several plant species. The genomes of several Trichoderma species have been sequenced and are publicly available Trichoderma colony in nature
Induced Resistance /(SAR= Systemic Acquired Resistance ), in Banana Plants – with Pathogenic Strain of Fusarium oxysporum (Janki Thakker 2013 ISRN Biotechnology ) The present study strongly supports the view of preparation of plant vaccines for combating devastating disease like Fusarium wilt of banana. Dead pathogen preparation was not only successful in mounting defense response but also in protecting plants upon subsequent infections. Therefore, it could be potential candidate for plant vaccine preparation to combat panama disease.