THE AGRONOMIC VARIABILITY IN GROWTH AND YIELD OF EXOTIC AND LOCAL CULTIVARS OF TOMATOES SOLANUM LYCOPERSICON L

CHAPTER ONE

INTRODUCTION

Introduction
1.1 Background of the study
Tomato (Solanum lycopersicon L.) is one of the most widely and important cultivated crop in Africa (Opena, et. al., 1990). Tomato is the world’s largest vegetable crop after Potato and sweet potato, but it tops the list chart of canned vegetables. In Nigeria Tomato is recorded as the important vegetable after Onion and paper (Fawusi, 1987). It is an important condiment in most diet and a few cheap source of vitamin, with a large quantity of water (%), calcium (%), and Niacin all of great important in the metabolic process of man.
Tomato can be grown in a variety of geographical zones in open filed or in greenhouses (screen house), and the fruit can be harvested manually or by mechanical means. In 2014, the global area cultivated with tomatoes was 5 million hectares with a population of 171 millions tones. The major tomato producing Countries are; China and India. (FAODSTATE, 2017). Under certain conduction such as pruning, weeding, irrigation, frost free environment, etc, the crop can be perennial or semi-perennial, but for commercial purpose. It is considered as annual (Geisenberg and Steward, 1986).
Although there are many types of growing system for greenhouse tomatoes, the two principle cropping systems are: “Two crops per year and one crop per year”, its significance doesn’t lie only on profit, but also in the income generated in the local economy for farmers and agricultural workers (Guldinez, 2013). There are several categories of protected vegetable production methods which provide some degree of control over various environmental factors such as: greenhouse, tunnels and covered field (Nieves-Garcia et. al., 2011). Although there is no quantitative record about the world’s vegetable production in greenhouse, some calculation have been made. For example, in 2012, the greenhouse vegetable production was about 81 million kilo-gram (kg), of which 40 million kg of the total production was tomato, and 37 million kg was cucumber. More so, In 2012, the tomato production in Northern America Accounting for about 52% of the market in Canada and 22% of the market in the United State (form credit Canada, 2012). But tomato production in Nigeria is low as compared to those of temperate zones due to differences in cropping environment conditions, lack of high yielding varieties, and cultural practices applied to the crops in the field.
Commercially, tomato fruit can vary in colour, size and shape (Vaughan and Heissler, 1997). The fruit contains large quantity of water, vitamin minerals such as hycopene (which gives the fruit it’s predominantly red colour) and beta-carotene (which contains up to 3% sugar of the fresh fruit weight). Tomato also contains tomatine and alcocide with fungicide properties. Tomatine concentration decreases as the fruit matures which helps to determine the taxonomy of the species. Therefore, if can be useful (OECD, et. al., 2018).
Tomato is one of the best studied cultivated dycotyledon plant of the molecular level and has been used as a model species for research into gene mapping, characterization (example pathogenic resistance gene) and gene transferred approaches. It is also useful to study other plant trait such as fruit ripening, hormonal function and vitamin by synthesis (Chetelat, et. al., 2006).

1.4 Origin and distribution of tomato
The edible tomato, often red berry of the plant solanum esculentum is a species originated from Western South America and Central America. Its domestication and uses as a cultivated food may have it indigenous to the Mexicans. From there, it was brought to Europe and to other part of the European-colonized world during the 16th century. Although there is no much history on how tomato was spread eventually introduced to Africa in the early 19th century and finally to Nigeria.
Tomato has been cultivated since prehistoric times with the earliest agricultural techniques and its cultivation and production keeps improving and evolving. This depends on several factors such as organoloptic properties of the fruits, farming system, agronomic practices etc. Modern age of commercially grown tomato started with the effort of Alexander W. Livingston. In 2009, worldwide tomato production rose to 158.3 million tons, surpassing the previous years by 3.7%. The largest producers were China with 24% of world production, followed by United States, Turkey, India, Egypt and Italy.
1.3 Health Benefits of Tomatoes
Tomatoes are a great source of vitamins
A single tomato can provide about 40% of the daily recommended minimum of vitamin C. What’s more, tomatoes supply vitamin A, which supports immunity, vision, and skin health; vitamin K, which is good for your bones; and potassium, a key nutrient for heart function, muscle contractions, and maintaining a healthy blood pressure and fluid balance.