Collection of Disease Diagnosis in Botanics - Case Study Example

COLLECTION OF DISEASE DIAGNOSIS Name: Course: Instructor: Institution: City: Date Table of contents Rhizopus Rot on Tomatoes 3 Symptoms 3 Field Situation 5 Weather Conditions 5 Pathogen 6 Control 8 Powdery Mildew 9 Symptoms 9 Field Situation 10 Weather Condition 11 Life cycle 11 Pathogen 12 Control 13 Calendula rust 14 Symptoms 15 Field Situation 16 Weather Conditions 16 Pathogen 17 Control 18 Rose mosaic 18 Symptoms 19 Field situation 20 Weather Conditions 20 Pathogen 20 Control 22 Disease caused by a post-harvest rot Rhizopus Rot on Tomatoes Host Solanum lycopersicum Name of the disease Rhizopus rot Pathogen Rhizopus spp. (mostly R. stolonifer) Rhizopus rot is widespread among vegetables such as tomatoes. Rhizopus spp. is classified as a saprophytic fungus. Rhizopus rot are normally caused by opportunistic pathogens such as Rhizopus spp (Baker, 1946). It is believed the Rhizopus spp. can survive for thirty years in the deposits of dried fruits. These fungi mainly attack a fruit that is stressed. The mechanical injuries that occur during Solanum lycoperscium cause the decay of the fruit since they provide site into which the Rhizopus spp. breed (Bustler, &, Bracker, 1963)). After the initiation of the lesion, the Rhizopus spp. can spread in the whole fruit causing total decay (McColloh, Cook, &, Wrught, 1968). Symptoms Rhizopus rot is a common post-harvest infection. The fungus is a wound invader or may penetrate through the unbroken fruit. Rhizopus stolonifer appears as white mold on the surface of Solanum lycopersicum. (McColloh, Cook, &, Wrught, 1968). The liquid from the decaying fruit is relatively clear (Baker, 1946). After sometime the decaying part turns black in colour. Ripe fruits are more prone to the disease compared to the green ones (McColloh, Cook, &, Wrught, 1968). A distinguishing characteristic of the Rhizopus rot is that it easily causes the fruit skin to slip from the decaying flesh underneath. Compared to brown rot which does not cause the fruit skin to slip from the decaying flesh underneath. Figure 1: Visual observation of Rhizopus rot Figure 2: Visual observation of Rhizopus rot (Surface and Inside) Field Situation Date: 25th, March Time: 12.00 A.M Location: Vegetables area of Queen Victoria Market, Melbourne Details: There were several tomatoes within the place of collection. The sample tomato was picked from a group of tomatoes that had shown signs of disease infection. The one that was picked shown severe symptoms and was considered the best for this study. Weather Conditions Rhizopus rot disease is normally favored by wet conditions and moderate weather conditions (Carlile, & Coules, 2012). The optimum temperatures for Rhizopus rot disease is15 and 30°C. Rhizopus rot in Solanum lycopersicum widely spreads at a time when there is less moisture in the place of the fruit storage. Pathogen Determination of whether the infection in a tomato fruit is a Rhizopus post-harvest infection, clear observation of the fruit body is necessary (Butler, &, Bracker, 1963). The Rhizopus rot normally produces a white or grey mold on the surface of a Solanum lycopersicum (McColloh, Cook, &, Wrught, 1968). The production of the grey or white mold is normally possible under moderate and wet weather conditions, usually 15 and 30°C. Rhizopus spp. was recently separated from common fruit fly known as Drosophila melanogaster (Carter, 1981). Figure 3: Sub-culture of tomato Figure 4: Sub-culture Rhizopus rot under a Microscope Subculture refers to a new cell made by transferring all the cells or some of the cells from a previous culture to a fresh growth medium. The aim of the subculture is to expand and or prolong the life cells in a culture. Subculture is normally used to produce a new culture with a lower density of cells that the original culture. Subculture is typically from culture; therefore, the structures of culture and subculture have similarities as evident in figure 4 and 5 below. Figure 5: Culture Rhizopus rot under a microscope The pathogen is classified under fungi, and mainly reproduces sexually. During the winter, mating takes place and the Rhizopus stolonifer produces zygospores (Bartz, 1991). The zygospores then germinate forming sporangiosphore whose sporangium contains spores (Bartz, 1980). Rhizopus stolonofer grows fast at a temperature of 15 and 30°C. Production of spores during summer and winter is high but lower during spring (Burtler, 1963). The pathogen therefore mainly attacks tomatoes during winter and summer. The pathogen can easily affect the adjacent tomatoes since wind and water can easily make it move from one point to another (Burtler, 1963). It infects other tomatoes once it gets into contact with the injured tomato part. Control Controlling of Rhizopus rot in tomatoes requires harvesting of the fruits immediately they mature (Baker, 1946). After the harvest, the fruit should be stored in a dry place to ensure there is no moisture that could facilitate breeding of the pathogens (McColloh, Cook, &, Wrught, 1968).The fruits should be stored at a temperature of 15 and 30°C.One should also clean and disinfect the containers used for the storage of the fruits. Burying of the debris of the fruits from the previous harvest also helps in controlling Rhizopus rot in Solanum lycopersicum (Bartz, 1991). Disease caused by a powdery mildew or another Ascomycete. Powdery Mildew Host: Syringa spp. Name of disease Powdery Mildew of lilac foliage Pathogen Microphaera alni Powdery mildew is a type of disease that affects wide range of plants for example lilac (Syringa spp.). Powdery mildew of lilac foliage is a fungal disease caused by a pathogen known as Microphaera alni. (Dixon, 1978). Powdery mildew is a type of plant disease that can easily identified by observation. The disease mainly affects the lower part of the leaf and the upper part of the leaf. Powdery mildew spreads well under moderate temperatures and high humidity (Gubler, &, Hirschfelt. 1992). Symptoms Infected lilac’s leaves develop grey or white patches or spots (Fennichia, &, Richard, 1977). The spots or patches enlarges during the summer period and by the time leaves fall they, all the leaves sides may be covered with a substance that is powdery white. After the leaves fall, they black or brown structures develop throughout the powdery parts (Cooke, et. al., 2006). The brown or the black structures that develop after the leaf fall makes up the fungus sexual fruiting bodies (Hill, &, Walter, 1997). The disease also causes leaf curling. The symptoms of the disease are mainly visible during the mid-summer period (Kliebler et. al., 2002). Figure 6: Visual Observation of powdery mildew, Lilac leaf Field Situation Date: 10th, April, 2015 Time: 8:30 A.M Location: Roadside, 86, Mt Alexander Rd, Travancore, 3032 Details: The sample leaf was picked from a plane tree. Leaves from where the sample leaf was picked had shown the symptoms of powdery mildew. Most of the affected leaves had dropped down. After picking of the sample leaf, storage was done in the kitchen and later brought into the laboratory on the 10th, April for the practical Weather Condition The causal agents of the disease are spread by wind. The disease mainly appears during late summer and autumn. In addition, the disease has been said to appear during warm days, cool nights and cloudy weather (Bob, 2011). Poor circulation of air, low UV radiation, high relative humidity and temperatures between 22-27°C accelerates the spread of powdery mildew in lilac leaves. Life cycle The pathogen overwinters in fallen leaves as partially developed ascospores. The spores only mature during wet spring weather conditions. After the spore’s maturity, they spread to the black fruiting bodies (Dixon, 1978). They are then blown by wind onto the uninfected foliage. After germination, haustoria of the fungus penetrate the leaf tissue and are restricted to a single layer of cells, which is the palisade layer (Hill, &, Walter, 1988). Asexual spores (powdery white) are then produced by the mycelium that grows on the leaf surface (Hill, &, Walter, 1988). The asexual spores produced are then dispersed by either rain or wind to other leaves within a plant, thus starting new infections (Guptac, &, Paul, 2202). This fungus develops well during summer and warm weather conditions. Figure 7: Life cycle of Microphaera alni Pathogen The symptoms of powdery mildew in a leaf can be identified through direct observation of an infected leaf (Dixon, 1978). Spots and patches on the leaf appear to be white, grey, cotton, or powdery, as can be observed in figure 6 above. To prove whether the disease is a powdery mildew, a microscope examination of the specimen is performed. From the examination, one can observe septate hyphae, an indication that the disease is a powdery mildew (Gubler, &, Hirchsfelt, 1992). A microscopic observation of the specimens provides figure 4 and 5. From the figures one is able to observe a chain of septate hyphae and conidia, a proof that the disease on the plane leaf is a powdery mildew and the causal pathogen in this case is Microphaera alni. These parasites are obligate parasites (Cooke, Jones, & Kaye, 2006). The Microphaera alni mycelium produces short conidiophore that also produces regular, round or oval chains of conidia resulting into a whitish appearance of the pathogen (Cooke, Jones, & Kaye, 2006). At the time of germination of conidial, production of short germ tubes apically terminating in lobed appressoria. Hyphal appressoria can appear lobbed or multi – lobbed as observed in figure 8 below. Figure 8: Hyphae of powdery mildew fungus, observation under microscope Control Powdery mildew does not have cure, but it can be controlled or prevented once observed on a plant leaf. The best way to prevent or control powdery mildew is to plant crops that are mildew resistant or mildew tolerant (Hill, & Walter, 1988). . The disease can also be prevented by ensuring application of nitrogen fertilizers during the early summer to inhibit production of succulent tissue, which is exposes, the leaf to infection (Cooke, Jones, & Kaye, 2006).. In addition, the disease can be prevented by exposing leaf to direct sunlight and exposing the leaf to free air circulation in order to inhibit germination of spores on the leaf surface (Hill, & Walter, 1988). . The infected leaves can also be picked directly in order to prevent further infections on the uninfected leaves of a plant. Failure of cultural control methods signifies the use of chemicals such as fungicides. Various fungicides have been used in the past, for example DMI fungicides, which attacks fungus during the early stages of growth and development (Fenicchia, &, Richard, 1997). Sulphur products (Bob, 2011) have also proved to be effective in the past; however, they only prove to be effective when applied before the appearance of the disease symptoms. Disease caused by rust Calendula rust Host calendula Name of disease Calendula rust Pathogen Puccinia distincta Calendula rust is a type of disease caused by Puccina distincta. Calendula rust is a type of rust fungus that is believed to have originated from Australasia and spread across the world (Peterson, 1974). Puccina distincta is a species that was recently separated from species P. lagenophorae. Symptoms Symptoms of calendula rust can be easily observed in an infected leaf. The infected leaf as shown in figure 9 and 10 below produces bright orange powdery pustules. The infected leaves if touch will leave ones finger with colored spot of the pores (Landon, &, Rainbow, 1969).  The disease also causes leaf curling as indicated in figure 9 below. Figure 9: Visual observation of rust, upper side of calendula Figure 10: Rust observed under a microscope Field Situation Date: 29th, April, 2015 Time: 1:00 P.M Location: CERES Environment Park, Cnr Roberts and Stewart Streets, Brunswick East, 3057. Details: The sample leaf was picked after observation and identification of the symptoms of calendula rust on the infected plant. Some of the symptoms identified were; leaf curling and powdery orange spots on the leaves. However, some of the calendula leaves were wilted, and symptoms not developed well posing a challenge for the disease diagnosis. Figure 11: Field situation of calendula Weather Conditions Rust infection on plants is highly experienced during mid-temperatures and high moisture. The spores of disease causing pathogen can be spread by water that splashes over long distances and wind (Thind, 2005). . The disease spreads rapidly at conditions with temperature of between 50 to 75 °F. Pathogen In identification of the pathogen, the symptoms observed were the same as those discussed before (Ian, 2012). As in figure 12 below, small, bright orange powdery pustules were observed under the microscope. Results of the microscope examination showed aeciospores that are polygonal with rough walls whose contents are orange yellow in color (Peterson, 1974). Aecium produces the aeciospores. Puccinia distincta affects plants under the family Asteraceae. The pathogen is said to have originated from Australia, however it is also widely spread in other countries in Europe such as Britain (Heath, 1977). Figure 12: Observation of puccinia distincta under a microscope The pathogen reproduces sexually during the spring winter and summer. It begins by producing basidiospores, and then pysiniospores develops to aecidiospores (Vogede, &, Mendges, 2003). All these takes place during spring. During summer, urediniospores (golden summer spores) are produced (Vogede, &, Mendgedes, 2003). Many generations of the pucinnita distincta are produced during summer. During winter, production of teliospores takes place (Vogede, &, Mendgedes, 2003). These are the spores responsible for blackening of the leaves Control Treating rust once it infects a plant is not easy. However, there are various ways through which infection of calendula rust can be controlled or prevented; these include avoidance of overwatering at the time of irrigation, ensuring continuous air flow in the region where the plants are located, removal of the affected leaves in a plant to avoid infection of other leaves, use of antifungal sprays to spray plants. These sprays however, are not very effective (Laundon, &, Rainbow, 1969). Mancozeb or Triforine fungicides can help reduce the infections but cannot completely eradicate the disease. Sulphur powder can also be applied on the plants leaves since it helps in inhibiting germination of the pathogens (Thind, 2005). Appropriate soil management and controlled plant watering can help in controlling calendula rust. To prevent infections of calendula rust, plants resistant to the infections should be planted (GRDC, 2008). Disease caused by a virus Rose mosaic Host: Rosae Disease: Rose mosaic Pathogen: Rose mosaic virus. Single or mixed infections with prunes necrotic ring spot viruse (PNRSV), Arabis Mosaic Virus (AMV) and apple Mosaic Virus (ApMV) Rose mosaic is a disease caused by a virus known as Rose mosaic virus. Rose mosaic is a disease found everywhere especially where rose flowers grow (Kenneth, 1986). The disease has high prevalence in Italy, Germany, Denmark, United States, South Africa, Netherlands, South Pacific, England and New Zealand. The disease spreads quickly in places with warm and moderate weather conditions (Kenneth, 1986). Rose mosaic affects the quality of flower produced. Symptoms Symptoms of rose mosaic vary widely from rose to rose; the symptoms of rose mosaic are widely determined by weather conditions and the conditions for the plant growth (Kenneth, 1986). The disease shows various symptoms on plants (Kenneth, 1986). Some of the symptoms shown by the infected plants include; mottles in the plan leaves, ring spots on the leaves and chlorotic line patterns on the plant leaves (Palti, 1981). The infected plants also show yellow mosaic and yellow net symptoms as shown in figure 12 below. At a high temperature above 21°C vein branding can occur on the infected plants (Palti, 1981). This can also be observed after a long period of virus infection. Rose mosaic virus does not affect the rate of flower production in mosaic plants but reduces the quality of the flowers produced. The symptoms of Rose mosaic disease are widely spread during the spring season (Kenneth, 1986). Comparison of an infected plant and healthy plant has shown that, the healthy plants are more vigorous than the infected plants Figure 13: Visual observation of Rose Mosaic Field situation Date: 16th, April, 2015 Time: 1: 00 P.M Location: Rose garden, trinity college, Royal Parade, Parkville VIC 3052 Details: The sample leaf was picked from the same plant when I picked two leaves for diagnosis of rose black disease. Most leaves on the plants did not show rose mosaic symptoms. The infected were wilted. Weather Conditions Symptoms of rose mosaic are mostly observed during the autumn and spring. Rose mosaic affects the whole plant; however, its symptoms are mainly evident on a plant during the time when the weather is cool (Kenneth, 1986). Cool weather favors the development of the virus. Pathogen Rose mosaic virus cannot be easily observed under a microscope. The infection of the virus can easily be identified by observation of its symptoms on the affected plants (Basit, &, Francki, 1970). Some of the symptoms that show the infection of the rose mosaic virus are, mottles on the plant leaves, yellow mosaic and chlorotic line patterns in the plant as indicated in figure 13 below. Rose mosaic virus (RMV) has been closely linked with Prunus necrotic ringspot virus (PNRSV) (Carlson, &, Davidson, 1995). Roses with single or multiple infections of PNRSV, RMV and Arabic Mosaic Virus (ARV) have shown have indicated similar symptoms (Kenneth, 1986). Apple Mosaic Virus, PNRSV and AMV therefore, separately or combined causes different symptoms of Rose mosaic on roses. PNRSV and Apple Mosaic Virus belong to the Bromoviridae family (Barara, 1981). Arabis Mosaic Virus belongs to the Secoviridae family. PNRSV causes leaf mottling, ring spots, chlorotic line patterns and vein banding on the leaves. A combination of PNRSV and AMV causes vein banding. PNSRV and ApMV can be detected using ELISA test. AMV however cannot be detected using ELISA test (Bharkaran et. al., 1974). Serologically Specific electron microscope is the instrument that can be used to detect AMV, PNRSV nand ApMV viruses. Figure 14: Rose mosaic virus as seen under a microscope Mosaic viruses are unable to survive outside their host (Barara, 1981). The mosaic virus reproduces sexually. The reproduction rate is normally high during winter (Kenneth, 1986). They overwinter on the infected rose plants. Insects or human beings mainly spread the virus from one plant to another. Control Specific cure exists for the mosaic viruses. The viruses however can only be controlled. The viruses can be best controlled by use of plants that are resistant to the virus infections (Kenneth, 1986). Control of the virus is also possible through removal of the infected plants (Barara, 1981). The use of virus - indexed propagative plants can also help in controlling the mosaic viruses (Palti, 1981). Buds free of the viruses can also be obtained through heat treatment of the infected plants (Basit, &, Francki, 1970). To obtain buds free from the viruses the infected plants should be held at a temperature of 38°C. The buds free from the viruses can be used to propagate cultivators. References Rhizopus Rot on Tomatoes Baker K. F. 1946. An epiphytotic of Rhizopus soft rot of green-wrap tomatoes in Carlifonia Plant Dis. Rep 30:20-26 Barksdale, T.H., J.M. Good, and L.L. Danielson. 1972. Tomato Diseases and Their Control. Agric. Handbk No. 203. A. R. S., U.S.D.A. Washington, D.C. Stall, R.E. 1991. Gray Mold, pp. 16-17. In J. B. Jones, Bartz, J. A. 1991. Postharvest diseases and disorders of tomato fruit, pp. 44-48. In J B. Jones, J.P. Jones, R.E. Stall and T.A. Zitter (eds.), Compendium of Tomato Diseases. APS Press. St. Paul Bartz, J.A. 1980. 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Vogele, R.T., and Mendgen, K. (2003). Rust haustorium: Nutrient uptake and beyond. New Phytol. 15993–100 Read More