CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

The tomato (Solanum lycopersicum L.) is a herbaceous plant of the nightshade family that is cultivated in many parts of the world for its fleshy fruit. The fruit is green when immature and turns bright red or yellow as it ripens. In Nigeria, as in many other countries, tomatoes are eaten raw in salads, used to garnish foods, and cooked in stews and sauces. They are a valuable source of minerals, vitamins, proteins and carotenoids, particularly lycopene, which has been linked to protection against several degenerative diseases (Ali et al., 2021).

The same properties that make tomatoes nutritious also make them highly perishable. Ripe fruits have a high water content and a soft tissue, which makes them easy for microorganisms to invade and difficult to store and transport. Fungi, yeasts and moulds are major agents of spoilage. As they grow, they use up the sugars in the fruit and convert them into products such as organic acids, alcohol and carbon dioxide, and the particular products depend on the organisms involved. Spoilage lowers the nutritional value and market value of the fruit and causes direct economic loss to farmers, transporters and traders. A recent assessment of the Nigerian tomato value chain found that stakeholders reported losses ranging from 12% among transporters to 27% among producers, although the figures differ from one study to another (International Fertilizer Development Center [IFDC], 2023).

Spoilage is also a food safety concern. Tomatoes are commonly consumed raw or in cold dishes, so contaminating or spoilage organisms on the fruit reach the consumer without any heat treatment. Some spoilage fungi are pathogenic or toxigenic, which means that the consumption of spoiled produce may pose health risks (Mailafia et al., 2017). Control of spoilage depends on factors such as the time of harvest, temperature and moisture during storage, the selection of produce before sale, and general hygiene during handling.

Several Nigerian studies have identified fungi associated with spoiled fruits. In Gwagwalada, Abuja, Mailafia et al. (2017) examined 100 spoilt fruits from the market and found Aspergillus niger (38%) and Fusarium avenaceum (31%) to be the most frequent isolates, followed by yeasts (10%), Fusarium solani (8%), Aspergillus flavus (5%), Rhizopus stolonifer (4%) and Penicillium digitatum (4%). They concluded that the pathogenic fungi found were of economic and public health importance. In Akwa Ibom State, Divine-Anthony et al. (2024) used cultural, morphological and molecular methods to identify fungal pathogens from five spoilt indigenous fruits, including tomato, and recorded genera such as Rhizopus, Aspergillus, Fusarium, Penicillium and Mucor. Their report also describes R. stolonifer as a soft rot pathogen of tomato in Nigeria that can colonise damaged fruits.

In spite of this evidence, fungi associated with spoiled tomatoes specifically in Gwagwalada have not been characterised in detail. The earlier Gwagwalada study covered several fruit types together (Mailafia et al., 2017). This study therefore isolates and identifies the fungi associated with spoiled ripe tomatoes sold in markets within the Gwagwalada metropolis, using morphological and biochemical characteristics.

1.2 Statement of the Problem

Tomatoes are an attractive cash crop for small-scale farmers and a source of income for many rural and urban people, and they are among the most widely marketed fresh vegetables. Even so, microbial decay after harvest is a serious cause of loss and reduces the quality of the produce. The extent of loss from microbial decay is often not measured in specific localities, and published estimates vary widely (IFDC, 2023).

In Gwagwalada, spoiled tomatoes are widely sold at low prices and are consumed daily by many residents as a cheaper substitute for good-quality fruit. Because many people eat tomatoes raw, the presence of pathogenic or toxigenic fungi on spoiled fruit is a potential public health risk. Yet information on the specific fungi involved in the spoilage of tomatoes in the area is limited. Without it, advice on handling, storage and control cannot be based on local evidence. This study addresses that gap.

1.3 Aim and Objectives

1.3.1 Aim

The aim of the study is to isolate and characterize fungi associated with spoiled tomatoes in Gwagwalada, Abuja.

1.3.2 Objectives

The objectives of the study are to:

1. isolate fungi associated with the spoilage of tomatoes; and
2. identify the isolates using their morphological and biochemical characteristics.

1.4 Research Questions

1. Which fungi are associated with spoiled tomatoes sold in Gwagwalada?
2. What morphological and biochemical characteristics identify the fungal isolates?
3. How frequently does each fungal species occur on the spoiled tomatoes sampled?

1.5 Significance of the Study

There is little information on the types of fungi associated with the spoilage of tomatoes in Gwagwalada, Abuja. Because spoiled tomatoes are eaten daily by many residents who regard them as an affordable alternative to good fruit, knowing which fungi are present is important for protecting public health. The findings will:

1. provide baseline data on the fungal species that cause tomato spoilage in the area, to support better handling, storage and marketing practices;
2. inform consumers, traders and health authorities of the potential risks of eating spoiled tomatoes;
3. contribute to efforts to reduce post-harvest losses by identifying the organisms that future control measures should target; and
4. serve as a reference for further research on tomato spoilage and its management.

1.6 Scope of the Study

The study is limited to the isolation and identification of fungi from spoiled ripe tomato fruits sold in markets within the Gwagwalada Area Council of the Federal Capital Territory, Abuja. Identification is based on morphological and biochemical characteristics. The study does not quantify post-harvest losses and does not test the toxin-producing capacity of the isolates, their susceptibility to antimicrobial agents or the effects of control measures.

References

Ali, M. Y., Sina, A. A. I., Khandker, S. S., Neesa, L., Tanvir, E. M., Kabir, A., Khalil, M. I., & Gan, S. H. (2021). Nutritional composition and bioactive compounds in tomatoes and their impact on human health and disease: A review. Foods, 10(1), Article 45. https://doi.org/10.3390/foods10010045

Divine-Anthony, O. M., Adegoke, A. A., Oduoye, O. T., & Akpor, O. B. (2024). Isolation, characterization and pathogenicity of fungal pathogens from indigenous postharvest fruits in Akwa Ibom state, Nigeria. Italian Journal of Mycology, 53, 29–44. https://doi.org/10.6092/issn.2531-7342/16813

International Fertilizer Development Center. (2023). Scoping and mapping of postharvest losses and Tuta absoluta related losses and the technologies for combating the losses. IFDC. https://ifdc.org/wp-content/uploads/2024/01/Scoping-and-Mapping-of-Postharvest-Losses-HortiNigeria.pdf

Mailafia, S., Okoh, G. R., Olabode, H. O. K., & Osanupin, R. (2017). Isolation and identification of fungi associated with spoilt fruits vended in Gwagwalada market, Abuja, Nigeria. Veterinary World, 10(4), 393–397. https://doi.org/10.14202/vetworld.2017.393-397