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1.2 Aim of the Study
To isolate and identify FUNGI ASSOCIATED WITHSPOT SYMPTOMS ON BAKERY PRODUCT.
1.3 Objectives of the Study
1. To observe different types of spot symptoms on bakery product.
2. To isolate and identify fungi associated with spot symptoms on bakery products.
1. Different types of spot symptoms were not observed on bakery product.
2. Fungi are not associated with spot symptoms on bakery product.
Spot is a common descriptive term applied to a number of diseases affecting Bread. The majority of spots are caused by fungi, but some are caused by bacteria. Some insects also cause damage that appears like a spot disease.Leaf spot may result in defoliation in some Bread(Nix, 2014).
Fungi causing spot diseases on different Breadinclude; Septoria, Alternaria,
Cladosporium, Rhizoctonia, Nigrospora,Cercospora, Phyllosticta, and
Ascochytaspp.(Singh and Allen, 1979; Allen et al.,1996; Howard and David, 2007; Verma and Gupta, 2008). Also Curvularia and Gleosporium spp.were reported to cause leaf spot (Olson, 1978; Akramet al., 2014).
2.2Symptoms of Spot Diseases
Spots come in a wide variety of shapes, sizes, and colors. A leaf spot disease creates spots on foliage. The spots will vary in size and color depending on the plant, the organism involved and the stage of the host plant development. Spots are most often brownish, but may be tan or black. Concentric rings or a dark margin around the spot may be present. Over time the spots may combine to enlarge and form blotches. Spots or blotches that are angular and located around the veins are generally referred to as anthracnose. (Stanley, 2014).
Alternariaspot on curcubits and cotton produces brown, grey or tan lesions (spots) on cotyledons, leaves and bracts varying from 1 to 10mm in diameter (Report of Plant Disease, 1989). The lesions appear first on older leaves as small circular spots which are light brown with light centers and form concentric dark rings as they enlarge thus the name “Target spot”. Lesions form on lower leaf surface tends to be more diffuse. Fruit infections begin as sunken brown spots and may later develop a dark powdery appearance as the fungus sporulates (Kucharek, 2000; Watt, 2013).Alternariaaternatawas reported on Cyperusrotundusand Cyperusbrevifoius.
Septoria spot produceslesions on wild blueberry and banana that are dark red, circular to irregular, 2-4mm in diameter, appearing similar on both leaf surfaces (Singh and Allen, 1979). Numerous small, water soaked spots first appear on the lower leaves, these spots soon become circular to angular with dark margins and grayish white centers often bearing one or more tiny black bodies called pycnidia, which are spore-bearing structures. Individual lesion is seldom more than 0.80cm in diameter and is usually quite numerous on an infected leaf (Report of Plant Disease, 1999; Ojiamboet al., 2007; Udugama, 2002).Wild blueberry leaf spot caused by Septoria sp, symptoms appears as small water soaked blisters on the bottom side of the leaf. The infected areas develop diffuse red margins (Wild blue berry Fact Sheet, 2007).
Cercosporaleaf spot produces circular to irregular cherry-red to reddish brown lesions up to 10mm diameter on cowpea (Singh and Allen, 1979). Individual leaf spots initially occur on older leaves and then progress to younger leaves are approximately 0.80cm in diameter with ash colored centers and purple to brown borders and circular to oval in shaped. It is distinguished from other leaf diseases by their smaller size and shape. As the disease progress heavily infected leaves initially turn yellow which may coalesce and form larger areas of dead tissue (Harveson, 2013).Grey leaf spot of maize caused by Cercosporazea-maydiscreate symptom that is small dark moist spots that are encircled by a thin yellow radiance which leads to discoloration (Ward et al., 1999).
Ascochytaspots are irregularly circular with grey to brown centers surrounded by a yellow halo. Such lesions become zonate and under favorable conditions spread rapidly causing extensive blighting of leaves, pods and stems of cowpea (Singh and Allen, 1979). The lesions develop also on petioles stem nodes peduncles and pods (Allen et al., 1996).Initial symptoms on the leaves are small circular reddish-brown spots which enlarge, becoming surrounded by irregular shaped water-soaked areas. Under humid conditions the lesions develop rapidly and coalesce (Singh and Allen, 1979; Allen et al., 1996). Basidiospore produces distinct small necrotic and circular spots which do not enlarge. Pods and seeds also bear lesions (Verma et al., 2006; Gonzalez et al., 2011).
Cladosporium sp. produces spot on eggplant, pepper and tomatowith irregular borders but when infection is severe these spots coalesced and kill large areas of the foliage. The upper surface of affected leaves turn olive green with more intense color near the center of lesions. Leaves eventually curl, wither, and may drop from the plant (Howard and David, 2007). Spots appear purplish-brown on the upper sides of leaves, on the lower side, spots are chestnut brown. Infection is generally more pronounced at margins of leaves (Jauron, 2012).
Nigrospora leaf spot appear in the form of small (2-5mm), circular to irregular red colored spots on leaflets, covering major area of the leaf on turf grass and cotton. Occasionally, the spots are seen delineated by midrib. In advanced stages of the disease, some spots cracked at the center. Eventually leaves dry and the plant defoliates (Nelson, 1992; Verma and Gupta, 2008; Zhengetal., 2012).
Black leaf spot caused by Diplocarponrosaeattack rose plant. It can attack any plant with fleshy leaves and stem if the conditions are right. It appears as tiny black spots on leaves no bigger than a pin head. As the fungus develops, those black spots are ringed with yellow. Soon entire leave turn yellow and falls (Rhoades, 2014).
Banana leaf spot (black sigatoa caused by Mycosphaerellafijiensisvar.difformishave been reported to vary according to location which reflect an important distinction between disease epidemics in temperate and tropical regions (Chuang and Jeger, 1987; Udugama, 2002; Mcmullen and Adhikari,2009).
All palms are susceptible to at least one of the pathogens that cause leaf spots and blight. Symptoms reported on palms are usually round to oval in shape and vary in color from yellow to brown to black (Rothrocket al., 1998).
Phyllostictacitricapahave been reported to cause citrus black spot on citrus. Symptoms on older leaves are small, round, sunken necrotic spots with grey centers bordered with dark brown margin; young lesions are small, reddish and slightly rose. Foliage lesions are most commonly seen in lemon (Citrus disease fact sheet, 2013).
Tabebuia tree leaf spot leads to symptoms that are brown or black spots and patches may be circular, with a water soaked or yellow-edge appearance (Jim, 2007).
2.5Ecology of Fungal Spot Diseases
Alternaria spot disease is favored by either repeated heavy dews or extended periods of wet weather. The fungi over winters as dormant mycelium in diseased and partly decayed crop refuse, in weeds and possibly in the soil. The conidia can survive under warm, dry conditions for several months. Conidia produced on diseased Bread or crop refuse may be blown by wind to long distances. The germinating spores penetrate susceptible tissue directly or through wounds and soon produce a new crop of conidia that are further spread by wind, splashing rain, tools or workers (Kucharek, 2000).At least 18hours of high relative humidity, producing leaf wetness is required before infection can occur. The periods of infection and the appearance of symptoms varies from 3 to 12days. Young Bread less than a month old and Bread that are bearingfruit and 70 to 75 days old appear to be more susceptible than Bread 45 to 60 days of age (Report of Plant Disease, 1989).
Frequent showers heavy dew, temperature of 68o to 85oF (20 to 29oC) and overcrowding of Bread favour the spread and development of Septoria leaf spot(RPD, 1999). The fungi may be carried on or in the seed or may overwinter in the soil or crop debris. In addition it also infect and over winter on several species of weeds as well as crops. The spores are spread by water splash, on tools and farm equipments and by handling of Bread (RPD, 1999). The severity of the disease is closely related to rainfall frequency and cool weather conditions (Sanderson et al., 1985).
Cercosporarequires periods of high humidity or leaf wetness periods longer than 11 hours and warm temperature (>60oF). Since leaf wetness is not routinely measured, relative humidity above 90% humidity can be used as a substitute. Very little infection will occur below 60oF or during periods of less than 11 hours of leaf wetness. Greater spore germination and leaf infection generally occur when night temperatures exceed 60oF and temperature is between 80o to 90oF (Harveson, 2013). Initial inoculum potential depends on the survival of the fungus spores and spore bearing structures (Psuedostromata) from the previous year’s infected crop residue, weeds may also be a source of inoculums. Spores can be carried by wind or splashing water to infect adjacent leaves and Bread. Life cycle may be complete within 10days (Harveson, 2013). Ascochyta is seed borne and also survives on straw. Secondary spreads occurs through rain splash. Infection depends on high relative humidity and cool temperature (21-24oC) (Allen et al., 1996).
Rhizoctonia survives between seasons which depends partly on the presence of crop debris, sclerotia and mycelium either on debris or free in the soil, are the main sources of inoculums. Infection follows splash inoculation with a range of weed species serving as source of primary inoculums (Allen et al., 1996).The disease appear due to prolonged periods of rainfall or high humidity above 50% and high night time temperature above 65oF (18oC). Rhizoctonia solani infestations can occur over a wide range of air temperature generally from 60-90oF (15-32oC) (Nelson, 1992). The pathogen require wet leaf surface or relative humidity of 95% to 100% and temperature from 25-32oC to infect plant tissue (Gross et al., 1998).
Cladosporium leaf spot occur in field when humidity is high. Fungal spores germinate under high humidity (85% or greater) and cool to warm temperatures (40 to90oF) but disease rarely occurs below 50oF. Wind splashing irrigation water and rain workers, tools and insects readily disseminate spores. Contaminated seed can also initiate epidemics. The pathogen survives between crops in crop residues and in the soil as spores (conidia) or dormant resting structures (Sclerotia) (Howard and David, 2007).
Periods of warm humid weather accompanied by nighttime temperature between 70-75oF
(21-24oC) and free water on the surface of the foliage may result in severe outbreaks of
Nigrospora blight (Nelson, 1992).
Concept of Fungi Infestation
Filamentous fungi involved in spoilage of bread include Rhizopus sp., and Mucor sp., Penicillium sp., Eurotium sp., Aspergillus sp. and Monilia sitophilia. One of the most common is Rhizopus stolonifer, often referred to as the ‘bread mould’. Storage of bread under conditions of low humidity retards mould growth. In addition to the economic losses associated with bakery products, another concern is the possibility of mycotoxins production. Eurotium species are usually the first fungi to colonize improperly water allowing other species. Aspergillus and Penicillium which can produce toxins to thrive. Losses of bakery products due to mould spoilage vary between 1-5 per cent depending on seasons, type of products and methods of processing. Members of the genus Bacillus bring about bacterial spoilage of bread known as rope. This is of major economic to the baking industry. Ropiness which is the most important spoilage of bread after moldiness occurs particularly in summer when the climatic conditions favour growth of bacteria. It is mainly caused by Bacillus subtilis but Bacillus licheniformis, Bacillus magaterium and Bacillus cereus have also been associated with ropy bread. The incidence of wheat bread spoilage caused by Bacillus has increased during the last few years presumably because more bread is produced without preservatives and often raw materials such as bran and seeds are added. Spoilage of bread by rope formation may constitute a health risk, high numbers of Bacillus subtilis and Bacillus licheniformis in foods may cause a mild form of food illness. Consumption of ropy bread has been association with food-borne illness in reports from Canada and the United Kingdom.
The stability of bakery products against the attack by fungi is mainly due to preservatives. Preservatives help to reduce or prevent wastage of food through spoilage caused by microorganisms. Longer shelf life enables a greater variety of products to be kept in store and in the home. Sofos and Busta (1991) reported that chemical preservatives can control the growth of molds by preventing the metabolism, by denaturing the protein of the cell, or by causing physical damage to the cell membrane. Among these preservatives are propionic and sorbic acid or their salts which have been show to increase the shelf life of bakery products. Propionic acid and calcium propionate are usually employed at concentrations of 0.1 and 0.2 per cent respectively. At these levels, moulds can be inhibited for 2 days or more and the formation of rope can be prevented. Sorbic acid is effective to control mold growth in bakery products at level of 0.125% to 0.3 per cent.
Problems due to spoilage yeasts in bread usually result from post-baking contamination, slicing machines, bread coolers, conveyor belts and racks have been identified as sources. Yeast spoilage is characterized by visible growth on the surface of products. The most frequent and troublesome yeast is Pichia butonii, which is known as “chalk mould”. This yeast can multiply rapidly on bread, with visible growth often apparent some time before mould occurs. Filamentous fungi are more common than yeast on British breads. Since, filamentous fungi are more easily recognized than yeast, because they generate the majority of complaints. The stability of bakery products against the attack by fungi is mainly due to preservatives. Preservatives help to reduce or prevent wastage of food through spoilage caused by microorganisms. Longer shelf life enables a greater variety of products to be kept in store and in the home.
ECONOMICAL IMPORTANCE OF BAKERY PRODUCTS
Bakery products are an important source of nutrients viz., energy, protein, iron, calcium and several vitamins. Commercial bread and biscuits contain around 7.5 per cent to 7.8 per cent protein respectively. Bakery products are good targets for fiber enrichment, as the decline of fiber consumption in the European diet is partially due to the refining of cereals. Most claims concerning fiber content refer to the inherent fibers from wholegrain flour. Fibers enrichment of several bakery products has recently been tested using an ingredient containing 95 per cent short chain fructo-oligosaccharides. These soluble fibers are naturally found in many vegetables including wheat, rye, onion, Jerusalem artichoke, and are structurally close to sucrose, therefore behaving like sugar regarding theology.
The economic losses associated with bakery products, another concern is the possibility of mycotoxins production. Eurotium species are usually the first fungi to colonize improperly dried, stored commodities, and when they grow, they increase the level of available water allowing other species (e.g. Aspergillus and Penicillium) to thrive. Eurotium sp. do not produce any significant mycotoxins. Hunt and Robbins (2009)  IJPBA, Jan - Feb, 2012, Vol. 3, Issue, 1 , told that bakery products accounted for approximately 9 per cent of total food expenditure, with bread king the most important, accounting for 27 per cents of each dollar spent. However, the consumption of white bread has decreased in the last two decades in western societies while sales of whole wheat bran bread have increased due to health concerns. Sales of flat breads, especially pita bread, have been increasing in western societies due to migration of cultures and societies. Several methods can be used to classified bread products including methods of fermentation, bread volume, and water activity.
In the last few years, the bakery products and flour confectionary sector has witnessed particularly intense technological progress which has brought clear and tangible changes, not only in terms of commercial and qualitatively characteristics of the products, but also in terms of process innovation. Usu
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