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Product Category: Projects
Product Code: 00009572
No of Pages: 55
No of Chapters: 5
File Format: Microsoft Word
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Sweet potato (Ipomoea batatas) is a tuberous rooted perennial crop that is usually grown as annual crop.This study was aimed to investigate the fungi associated with the spoilage of sweet potatoes in Dutse town focusing on isolation, identification, and pathogenicity assessment of the isolated species. Samples were collected from three distinct locations: Sabuwar Kasuwa (1, 2, 3), Yan Tifa (1, 2, 3), and Hakimi Street (1, 2, 3), with a total of nine samples analyzed. Through culturing techniques on SDA, three significant fungal species were isolated: Aspergillus sp., Aspergillus niger, and Rhizopus stolonifer. The identification process involved both macroscopic and microscopic examinations, confirming their roles in post-harvest spoilage. Comparative analysis revealed significant differences in fungal loads among the sampling locations, with Hakimi Street exhibiting the highest contamination levels (7.0 x 104 CFU/g), followed by Sabuwar Kasuwa and Yan Tifa. Pathogenicity tests demonstrated that all isolated fungi were capable of causing spoilage; however, Rhizopus stolonifer was identified as the most aggressive pathogen, leading to rapid decay and substantial weight loss in sweet potatoes (15.0%). These findings highlight the impact of fungal contamination on sweet potato quality and marketability, emphasizing the need for effective management strategies to mitigate spoilage. To reduce fungal contamination, it is recommended that farmers and vendors adopt better storage conditions, such as maintaining lower humidity levels and ensuring proper ventilation and future studies should explore the specific environmental factors contributing to higher fungal loads at various locations, as well as investigate additional antifungal treatments that could be applied during storage.
Table of Contents
1.3 Justification for the Study
2.1 Origin and Taxonomy of Sweet potato
2.2 Description of the Sweet Potato Plant
2.3 Importance of Sweet Potato in
Sub-Saharan Africa
2.4 Nutritional Composition of Sweet
Potatoes
2.5 Production of Sweet Potatoes
2.6 Factors Affecting Sweet Potato
Production
2.7 Postharvest Microbial Deterioration of
Sweet Potato
2.8 Factors Affecting Postharvest Microbial
Deterioration of Sweet Potato
2.8.1 Environmental or Cultural Stress
During Root Development
2.8.3 The Type of Sweet Potato Cultivar
2.8.4 Handling/Mechanical Injuries Factor
2.8.6 Storage Temperature/Relative Humidity
Factor
2.9 Microorganisms Associated with
Postharvest Deterioration of Sweet Potato
2.10 Implications of Microbial Spoilage of
Sweet Potato to Food Security
2.10.1 Reduction in Food Produce
Availability
2.10.2 Compromises Food Quality and Nutrition
2.10.3 Compromises Food Safety
2.10.4 Adverse Effect on the Economic Value
of the Crop
2.10.5 A Wasted Investment that Reduces
Economic Access to Food
2.11 Postharvest Disease Management
Strategies
2.11.1 Good Agricultural Practices
2.11.3 Prestorage Treatment of Sweet
Potatoes
2.13 Alternative Control Strategies
2.13.1 Antagonistic Microorganisms
2.13.2 Secondary Compounds in Plants
3.2 Isolation and Identification of
Associated Fungi
4.1.1 Isolation and Identification causing
spoilage of Sweet Potato
Table 4.1: Macroscopic and Microscopic
Features of Fungi Isolated from spoilt Sweet Potato
4.1.2 Fungal Load Between Sampling
Locationsan
Table 4.2: Fungal Load Between Sampling
Locations
4.1.3 Pathogenicity test result
Table 4.3: Pathogenicity Assessment of
Isolated Fungi on Sweet Potato
Table 4.1: Macroscopic and Microscopic Features of
Fungi Isolated from spoilt Sweet Potato.. 36
Table
4.2: Fungal Load Between Sampling Locations.................................................................. 37
Table 4.3:
Pathogenicity Assessment of Isolated Fungi on Sweet Potato.................................... 38
Sweet potato (Ipomoea batatas) is
a tuberous rooted perennial crop that is usually grown as annual crop. It
originated from Central America (Ecocrop, 2010) and is widely grown as an
important staple food in most parts of the world. There are over 403 varieties
of sweet potato of which the flesh can be white, yellow, red, purple, pink,
violet and orange or brown while the skin colour varies among yellow, red,
orange and brown (Ecocrop, 2010). The crop has great food and health values.
Many parts of the plant including the leaves, root and vines are edible. The
roots are widely used as carbohydrate food; the tender leaves commonly eaten by
man while the leafy stems are fed to livestock (Woolfer, 1992). Beside these,
the crop has been noted to provide surprising health benefits including fighting
cancer, diabetes, vitamin A deficiency, and inflammation; preventing
arteriosclerosis, heart disease, depression, emphysema, arthritis, stroke,
muscle cramp and stomach ulcers; reducing arthritis and inflammation and curing
bronchitis and stomach ulcers (Alum et al., 2013).
The population of Nigeria relies on
sweet potato as a food security crop (Adeyonu et al., 2016).
Unfortunately, sweet potato roots are susceptible to many microbial infections
at different stages including field, harvest and storage (if they are not
properly harvested and stored) and marketing stages. This type of spoilage
commonly associated with sweet potatoes is a major constraint to the potential
of sweet potato as food and health security crop (Echerenwa and Umechuruba, 2004).
This result in many detrimental effects including deterioration in food quality
characteristics, great loss in storage roots, unavailability of food produce
during off-season and a waste of farm inputs and scarce resources such as
water. It also saps human effort and investments and adversely affects the
people‟s economic access to crop produce. Microbial spoilage also compromises
food (sweet potato) safety; posing a serious health concern (Walsh et al.,
2004; Jain et al., 2011; Esnakula et al., 2013; Esnakula et
al., 2013 and Georgiadou et al., 2014).
Due to the negative economic importance of fungal pathogens, control strategies are needed. Several postharvest pathogen control methods used include fungicide treatment, gamma irradiation and hydro-warming. These methods, though reported to have intermediate impacts in controlling spoilage and enhancing shelf life of sweet potato tubers (Ray and Ravi, 2005), have some drawbacks including unavailability to Nigerian farmers, unfriendly to environmental sustainability, phytotoxic to man and a great propensity to trigger resistance in the targeted pathogens (Okigbo and Nmeka, 2005). Given these drawbacks associated with the orthodox fungi and rot control approaches, focus hasin recent times, shifted toward exploitation of plant extracts as novel fungicides in plant protection (Okigbo and Nmeka, 2005; Okigbo and Omodamiro, 2006). Many botanicals have been extensively researched on and proved to possess antimicrobial properties; hence myriads of reports have been documented stating the uses of plant extracts to control plant diseases. Some plants tested for antimicrobial properties include Chromolena odorata (Siam weed), Ocimum gratissimum (wild basil), Moringa oleifera (moringa) and Zingiber officinale (Ginger) (Okigbo and Nmeka, 2005; Okigbo et al., 2009a).
Microbial pathogens affecting crops tend to vary in occurrence and distribution depending on the environment, crop physiology, harvesting and storage, thus the incidence of postharvest rot disease, the frequency of occurrence of different pathogens and their importance as primary pathogens of decay may change with reference to location. Therefore, to develop an effective disease control programme for the sweet potato sector, it is important to know the fungal pathogens responsible for the disease within a location. Moreover, the development of potent and drawback-free decay control measures is critical to prevention of microbial spoilage and reduction of food losses to microbial attack. In spite of these recognitions, the occurrence and control of fungi associated with sweet potato spoilage seem not to have received attention; yet there is apparently a steady increase in post-harvest microbial spoilage of sweet potato observed and reported by some farmers in the area. Attention to postharvest rot control has been focused on the use of single plant extracts with antimicrobial activities that were always far less +potent than those of synthetic chemicals employed as treatment checks in several investigations. Moreover, the antimicrobial activity of plant extracts that is observed in in-vitro conditions is quite different from its effect in complex food systems. In most cases antimicrobial activity is decreased due to interactions with food components. This could be a challenge in utilizing plant antimicrobials, as a higher concentration could result in unfavorable changes to the taste and aroma of food (Havelaar et al., 2010). Combinations of extracts can lead to additive or synergistic effects on postharvest pathogens. Despite these recognitions, literature in Nigeria still lacks sufficient data on the potency of combined plant extracts against microbial spoilage pathogens for use in sweet potato preservation.
1.3 Justification for the Study
The developing nations of the world have always been in short supply of food. Around 1 billion people are being faced by severe hunger in these nations of which 10% actually die from hunger-related complications. This problem is further compounded by the accelerated increase in human population, which creates pressure on every form of food supply (Urom, 2014). Today, one of the main global challenges is how to ensure food security for a world growing population whilst ensuring long-term sustainable development. According to the Food and Agricultural Organization, food production will need to grow by 70% to feed world population which will reach 9.3 billion by 2050. Worse still, in the meantime, while the number of food insecure population remains unacceptably high (FAO, 2010), each year and worldwide, massive quantities of food including sweet potatoes are lost due to spoilage and infestations from farm to folk. This problem arises due to inadequate agricultural storage and microbe-induced spoilages (Kana et al., 2012). Studies that will generate baseline information on the occurrence of postharvest spoilage fungi of sweet potato and a potent drawback-free strategy for controlling the rot pathogens are critical to reducing sweet potato yield losses at postharvest. The potential benefits of reducing postharvest losses of sweet potato to mycodeterioration are large. It is critical to alleviation of poverty while reducing pressure on ecosystems, climate and water. It is also a strategy for contributing to food security enhancement and closing the food gap between food available today and food needed in 2050 to adequately feed the planet’s projected 9.3 billion people.
The study was aimed to isolate,
identify, confirm and characterize the fungi associated with the spoilage of
sweet potato.
1.4.2
Objectives
The objectives of the study were to:
i.
Isolate and
identify the fungi associated with the spoilage of sweet potato.
ii.
To compare the
fungal load between sampling locations.
iii.
Determine the
pathogenicity of the isolated fungi.
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