1.0 INTRODUCTION
Tomatoes are vegetables grown in the
northern part of Nigeria. The word ‘tomato’ may refer to the plant (Solanum lycopersicum) or the edible
typically red fruits that it bears. Tomato can be classified as follows:
Kingdom:
plantae
Order:
Solanales
Family: Solanaceae
Genus:
Solanum
Species: S.lycopersicum
Synonyms:Solanum
lycopersicum L.(1753)
Lycopersicon
(H.Karst, 1882).
The
genus Lycopersicon, comprising nine (9) species, has its origin in the South
American Andes, from Central Ecuador through Peru to Northern Chile. Tomatoes
which can be planted in cool and dry regions are also grown at homes, in the
garden and also commercially in the fields for sales, also tomatoes have many
uses; they can be consumed raw or fresh in salads or cooked in sauces and also
are used for flavoring in soups, stew and sometimes in meat and fish dishes. Tomatoes
also can be used in wines. Economically, they are equally important are the
processing forms such as purée, juice, ketchup and canned whole. Tomatoes are
considered a vegetable for culinary purposes. The tomato vegetable is rich in
lycopene which has beneficial health effects. Tomatoes are said to belong to
the nightshade family.
Tomato
plants have erect on prostrate stems up to 2-4m long, its’ taproot stretches up
to 0.5m deep or more, with a dense system of lateral and adventitious roots. It
has a weak stem that often sprawls over the ground and vines over other plants.
It is said to be perennial in its native habitat, although often grown outdoor
in the temperate climates as an annual crop. The world tomato production in
2001was about 105 million tons fresh fruit from an estimated 3.9 million
hectare. Leading countries in tomato production are:
China
------------------------------------------934,000ha
India
-------------------------------------------500,000ha
Turkey
-----------------------------------------225,000ha
Egypt
------------------------------------------181,000ha
USA
-------------------------------------------164,000ha
In
2001, world exports of fresh tomato fruits were estimated at 4million tons,
valued at 300 million US dollars mainly from Spain, while Netherlands’ and
Mexico with about 600 million US dollars. Also, the area used for tomato
production in tropical Africa is about 300,000ha with an estimated annual
production of 2.3million tons. Nigeria being the largest producer of tomato
with 126, 000ha and an annual production of 879, 000 tons of fresh tomato. (World
tomato production 2001)
There are about 7500 tomato varieties
grown for various purposes around the world. Tomato varieties are roughly
divided into several categories, based mostly on shape and size. Tomatoes are
commonly attacked by pest and disease, such insect pest that attack tomato are:
stink bugs, cutworms, tomato hornworms, tobacco hornworms, aphids etc.(Hahn and
Fetzer 2009). When insects attack tomato plants, they the plant peptide hormone
system in which activates defensive mechanisms such as the production of
protease inhibitors to show the growth of insects (Narvaez and Cardenas 2008)
the common diseases of tomato include: verticullium wilt, fusarium wilt, alternaria
and root-knot nematode disease (Pleger et
al 2008).
Tomatoes
can and are easily infected by nematodes. When the roots of the plants are
severely infected by the root-gall nematode, the normal root system is reduced
to severely galled roots with a completely disorganized vascular system. Growth
is retarted and leaves become chlorotic (Nestscher 1971). Meloidogyne attack causes
50-70% losses to tomatoes and approximately 5% of global loss in tomatoes and
other vegetables (Sasser J.N 1989). Although 51 species of meloidogyne have
been described to date (Jepson, 1987). Four (4) species of the meloidogyne are
of particular economic importance.
These
includes:-
Meloidogyne
incognita
Meloidogyne
javanica
Meloidogyne
hapla
Meloidogyne
arenaria(Luc
et al 1990)
Also root-knot nematodes (meloidogyne
spp) cause histopathological changes in root tissues of tomatoes. The results
of these changes are the formation of giant cells and for galls in the root
system. This abnormality can upset the normal physiological activities of the
vascular tissues of the root system and may finally cause wilting, stunting
,leaf chlorosis and poor growth (Ekanayake et
al 1938) The ability of Meloidogyne
spp to infect their host depends on the factors such as initial nematode
population ,plant varieties or cultivars (resistance or susceptibility), age of
the plant host at the time of infection and nematode activity. Besides direct
damage, root-knot nematodes serves as a predisposal agent in development of
other disease. The disease complexes produced by interaction of nematode with
pathogenic bacteria or fungi are more damaging to plants than these pathogen
acting alone. (Siddiqui, 1998, Noel and Edward,1989). In certain situations,
the nematode has been responsible for breaking disease resistance to fusarium
wilt. Varieties of the same crop differ in their responses to root-gall
nematode infection. Agu (2010) reported that the four landrace of Dioscorea rotundata exposed to Meloidogyne incognita infection differed
in their galling responses to the nematode. Odihirin (1981) also reported some
cowpea varieties: TVU 857 and 841 with natural immunity or tolerance to both Meloidogyne incognita and Meloidogyne javanica. These reports are suggestive
that crop varieties vary in their inherent genetic resistance status to
root-gall nematodes. Little or nothing is known about the
resistance/susceptibility statues of the commonly grown tomato varieties in
Abakaliki agro-ecology to root-gall nematode infection. This study was therefore
concerned with the evaluation of three (3) tomato varieties against root-gall
nematode infection in Abakaliki Agro-ecology.
Specific
objectives
1. To ascertain the degree of
susceptibility/resistance of the three (3) tomato varieties to meloidogyne spp.
2. To investigate the effect of root-knot
nematode on the three (3) tomato varieties
1.1 OBJECTIVES
OF THE STUDY
1. To evaluate the
susceptibility/resistance of three (3) commonly grown tomato varieties to
root-knot nematode disease in Abakaliki Agro-ecology.
2. To make recommendation/s based on the
variety yield and susceptibility to root-gall nematode for possible adoption by
farmers. There are no specific objects