Tomato (Solanum lycopersicum Mill ) is a solanacious plant. The fruit is very rich in essential vitamins and mineral salts (Peet,2001). It generates income to its growers. It is tropical warm season crop, said to have originated in tropical Central and South America(COPR,1983), and it is grown all over Nigeria. The bulk of production is from the dry season cropping particularly under irrigation in the Northern states and near riverbanks in the southern states of Nigeria. According to COPR(1983),the total land area covered annually is over one million hectares with most of the production from the Northern Guinea Sudan Savannah. The area of land used for tomato production in tropical Africa is about 300,000 hectares with an estimated annual production of 2.3 million tonnes. Nigeria is the largest producer with 126,000 hectares and annual production of about 879,000 tonnes ( Van der Vassen et al.,2004). The average yields in local farms range from 5 to 10 t/ha, while 30 t/ha have been recorded in research farms ( Adeyemi, 2010).
Uguru (1996) stated that tomato is a short –lived herbaceous annual with weak trailing much branched stem with hairs at juvenile stage of development. Tomato is a warm season crop that grows well in areas with evenly distributed rain fall and with long period of sunshine. Fruits of local varieties in Nigeria are thin-walled, heavily seeded and sour in taste. Tomato fruits contain high level of vitamins A, B, and C (Erince, 1999). Purseglove (1998) reported that tomatoes were used in large quantities to produce sauce, ketchup, puree and juice. Green tomatoes are used for pickles and the seeds are extracted from the pulp are used in canning industry. Tomato is one of the most important vegetables grown for edible fruits consumption in virtually every home in Nigeria. Its production in South Western Nigeria is concentrated mainly during the hot raining season (Ahmad and Singh, 2005). According to Adelana (1976), tomato is usually grown in Southern part of Nigeria in small holdings in farms and gardens under rainfed conditions while it is grown in the Northern States under irrigation.
Tomato grows well in many types of soils ranging from sandy to the heavy clayey soils (Uguru,1996). Well drained, fertile soils, with good moisture retaining capacity and high level of organic manures are required for the production of tomato ( Tindal, 1998). Soil is generally a favourable habitat for the proliferation of saprophytic and pathogenic micro-organisms, such as viruses, bacteria, fungi, algae and protozoa (Atlas and Bartha,1993). Soil also supports plant life by providing nutrients and mechanical support. It is one of the vast dynamic sites for biological interactions in nature. Many biochemical reactions which result in distribution of organic matter and nutrients normally occur in the soil. Jaraba et al.,(2007) reported that sand to sandy-loam soils are conducive to Meloidogyne species .
The production of tomato is limited by the attack of pest and diseases. This results in acute shortage of the fresh fruits in certain periods of the year. Yield losses are partly attributed to the susceptibility of tomato cultivars to serious pests and diseases (Udo, 2004). More than a hundred different pest species have been recorded worldwide on tomato crops(Peet,2001; Udo,2004). They include nematodes, mites, thrips, aphids, moths, whiteflies, beetles and flies (COPR, 1983; Kessel,2003).
Nematodes are one of the major pests of tomato globally especially in the tropical and subtropical regions. The production of tomato is impaired by among other factors its infections by nematodes (Abubakar et al., 2004). Adesiyan et al.,(1990) reported reductions in yield ranging from 28 to 68%. Over sixty species of plant parasitic nematode attack tomato but the most destructive nematodes responsible for enormous yield losses of tomato are the root-knot nematodes belonging to the genus, Meloidogyne (Sasser 1989. Dufour et al.,., 2003; Udo, 2004).
Udo (2004) stated that about 29-50% overall yield reduction of tomato in the tropics is attributed to the root-knot nematodes. Root knot nematodes (Meloidogyne spp.) are small microscopic roundworm organisms grouped as a major pathogen of vegetable crops throughout the world, affecting the quantity and quality of marketable yields (Kingland, 2001). They infect plant roots by producing galls through their feeding habits (Nesmith, 2000). These nematodes are responsible for a greater yield loss of tomatoes when they infest plants at the seedling stage (Vavring, 1991; Mullins, 2000; Dufour et al., 2003). According to Adesiyan et al., (1990), nematodes can predispose plants to infections, break disease resistance, act synergistically in the development of the disease or are vectors of the disease organisms.
Nematodes in agricultural soils have been controlled using such measures as chemicals like furadan, sincocin and oxamyl which are very expensive and misapplication might result in an adverse effect on the environment. Pyrethriods and other newly developed safer pesticides are expensive. Other control measures like use of biological agents (Verticillium chlamydosporium and Arthrobotrys oligospora), resistant varieties, botanicals, organic manures, crop rotation and time of planting are also employed in controlling plant pathogenic nematodes in the soil. Atungwu (2006) reported that several organic materials have been effectively used for the management of nematode pests of crops throughout the world. Atungwu et al., (2010) stated that although chemical control gives instant reduction of nematodes, its expensive cost forces farmers to exploit indigenous control methods. Other alternative control measures which are cheaper, available and environmentally friendly should therefore be developed and used in controlling nematode attacks on tomato to ensure higher productivity and sustenance of the crop. The objectives of this research are therefore to:
- evaluate the efficacy of some aqueous leaf extracts in controlling root-knot nematode infections on tomato.
- evaluate the effect of different soil amendments in controlling root-knot nematode infections on tomato.
- evaluate the effect of different coloured polyethylene mulches in controlling root-knot nematode infections on tomato.
Tomato, a solanacious crop, originated in tropical Central and South America, but first domesticated in Mexico and later taken to Europe and across the pacific by the early Spanish explorers and Portuguese traders. The crop has increased in popularity in the tropics and sub-tropics and is now the second most important vegetable crop in the area ( COPR, 1983; Taber et al.,1998; Udo, 2004).
Tomato is a herbaceous plant. It is commonly grown as an annual though perennial tomato culture is an established practice in many parts of South America ( Peet, 2001). Atherton and Rudich (1986) stated that the stem is covered with glandular hairs and typically about 4cm in diameter. At the tip of the main stem is the apical meristem, a region of active cell division where new leaves and flower parts are initiated. Kessel (2003), reported that the leaves are covered with hairs and the lowest two or three leaves may be small with few leaflets. Many smaller leaflets or follicles may be interspersed with large leaflets. The leaflets are usually petiolate, serrate-with toothed edges. According to Anaele (2007), tomato plant has a tap root system with lateral roots arising behind the growing root tip. Adventitious roots, similar in structure to the lateral roots, develop in favourable conditions from the stem particularly near the base. The inflorescence of tomato is formed terminally on the shoot. The tomato fruit is a berry composed of flesh (pericarp walls and skin) and pulp (placenta and locular tissue including seeds). The pericarp consists of an exocarp or skin, parenchymatous mesocarp and a single celled layer of endocarp lining the locules. The seed is a flattened ovoid structure about 5mm long, 4cm wide, and 2mm deep consisting principally of embryo, endosperm and testa or seed coat. The embryo comprises the root or radicle, hypocotyl, two cotyledons and the shoot apex.
2.0.1. ECONOMIC IMPORTANCE OF TOMATO