CHAPTER ONE
INTRODUCTION
Tomato (Lycopersicon sesculentum L.) of the family Solanaceae is an important commercial crop in the world. Nutritional values of tomato make it a widely accepted vegetable by consumers. Nevertheless, tomato is a very perishable vegetable with a short shelf-life and high susceptibility to fungal diseases. During prolonged storage, tomato is susceptible to post harvest diseases caused by various pathogenic fungi. Tomato is one of the most perishable and second most important vegetable worldwide, in terms of the amount of vitamins and minerals it contributes to the diet. However, consumers are not satisfied with the quality of tomato (Sozzi and Fraschina, 1997).
Many fruits and vegetables are perishable especially in tropical and subtropical regions where they are cultivated and are without adequate refrigeration. The magnitude of post harvest losses in fresh fruits and vegetables is estimated at 25.80% (Thirupathi set al., 2006). Most of the products are lost after the harvest because of inadequate handling and preservation methods (Matthew, 2011) and also, it is extremely difficult to harvest fresh tomatoes and other vegetables without causing injury. People in developing countries often cannot afford the use of cold storage facilities (Matthew, 2011).This may be due to lack of capital or lack of technical knowledge.
Fruit rots are generally caused by pathogens that normally colonize dying or dead organic matter. The pathogens can, however, infect tissues that are wounded and exposed without protective surfaces. Mechanical injuries (e.g. cuts and bruises) that occur during harvest and handling are common sites for decay development that begins on the fruit surfaces (Jerry et al., 2005). By contrast, internalized pathogens (those that have penetrated tissues beneath the fruit surface) cause lesions that begin inside the fruit. Lesions may expand to engulf the entire fruit. Usually, the rapidly developing lesions that cause major loss of texture (soft rot) progress until the fruit collapses (Jerry et al., 2005). During lesion development and progression, structure and materials are produced that spread the decay to adjacent and nearby fruits, leading to other infections.
Fruits and vegetables vary in their innate resistance to decay and are most resistant when relatively dry and firm. Mature green tomatoes are more resistant to most decay pathogens than ripe fruits. Over-ripe tomato fruit may be attacked by organisms that normally are not considered decay pathogens of tomatoes (Jerry et al., 2005). Fruits and Vegetables have a limited post harvest life, during which they no longer receive water or nutrients from the plant. Naturally occurring senescence in produce leads to a softening of tissues and often loss of preformed antimicrobial substances (Jerry et al., 2005). These changes in the fruit or vegetable also make it less desirable to consumers.
Post harvest diseases destroy 10-30% of the total yield of crops and in some perishable crops like tomato especially in developing countries; they destroy more than 30% of the crop yield (Kader, 2002; Agrios, 2005). The quality of tomato is affected by post harvest handling, packaging, storage and transportation which may result in decay by micro organisms which become activated because of the changing physiological state of the fruit (Matthew, 2011). Fruits, due to their low pH value, high moisture content and nutrient composition are very susceptible to attack by pathogenic fungi, which in addition to causing rots, may also make them unfit for consumption by producing mycotoxins (Moss, 2002). Careful post harvest handling is the major but often neglected step towards offering a greater volume of nutritious food to mankind and to prevent loss between harvesting and consumption. Fungi are the most important and prevalent pathogens, infecting a wide range of host plants and causing destructive and economically important diseases of most fresh fruits and vegetables during storage and transportation (Matthew, 2011).
