INTRODUCTION
Vegetables
constitute commercially and nutritionally important indispensable food
commodity. Vegetable naturally play a vital role in human nutrition by
supplying the necessary growth factors such as vitamins and essential minerals
in human daily diet and that can help to keep a good and normal health.
Vegetables are widely distributed in nature. One of the limiting factors that
influence the fruit economic value is the relatively short shelf-life period
caused by pathogen’s attack (Droby, 2006: Zhu, 2006).
Tomato (Lycopersiconesculentum) pronounced
Toh-MAH-to is the most important vegetable worldwide. Tomato is an annual plant
which belongs to the Solanaceaefamily
which includes other well-known species such as Potato, Tobacco, Pepper and Egg
plants (aubergine) and can reach a height of over two meters. It’s a berry
fruit, tomato is grown mainly in soil (Frazier and Westhoff,2004).
Tomato is essential
mainly for its dietary needs and can be consumed in diverse ways. It can be
cooked as vegetable, as an ingredient in many dishes and sauces; in the making
of stew, fruit juices and can be eaten raw in salads(Masefield et al., 2002).
The
modern day tomatowhich is a very popular fruitoriginated from South-Western
Hemisphere, now the Peru-Euador area(Rick,2001).From here,it was distributed to
many parts of tropical America. It possibly arrived the West African Ports via
Portuguese traders or the Sudan (Tindall, 2004).
Tomato
in West Africa is grown in gardens and irrigation schemes. In Nigeria, most
tomatoes are grown in the northern parts of the country(Erinle,2007) and there
is no record of any systematic or organized traditional storage method for
vegetables and fruits. They are usually sold immediately after harvesting. They
are packed in baskets, cardboard boxes, or wooden crates ready for
transportation to the markets.
Tomato
is the most perishable vegetable during handling, transportation and storage.
This is because tomato contains large amount of water which makes them
susceptible to spoilage by the action of microorganisms such as fungi, bacteria
and protozoans (Ross, 1975). Estimates have shown that about one third of the
produce is lost before reaching the consumer (Erinle, 2007), this loss has been
attributed to a number of factors which include physical (mechanical breakage,
bruises), physiological and also damages caused by pathological agents (Thompson
and Kelly, 2000), market value of the tomato are mainly reduced by this
factors.
Watt
and Merrill, (2000) defined spoiled food as that which have been damaged or
injured so as to render it undesirable for human consumption. Various
activities may result in food spoilage: insect activities,causing physical
injuries for example, bruisingand enzyme activity by microorganism causes
change in colour, taste, smell, texture and quality of the food.
Pauland
Sarisbury, (1981) also referred to
spoilage as any change in the condition of food in which the food becomes less
palatable or even toxic: these changes may be accompanied by alteration in
taste, smell, appearance or texture.
The
spoilage of food by microorganisms should not be viewed as a sinister plot on the
part of the microbes deliberately to destroy foods but as a normal function of
these organisms in the total ecology of all living organisms (Watt and Merrill,
2000). It has also been estimated by Watt and Merrill (2000) that 20% of all
fruits and vegetables harvested for human consumption are lost through
microbial spoilage causing one or more of 250 market diseases. Spoilage of
fresh tomato usually occurs during storage and transit and also while waiting
to be processed.
Frazier
and Westhoff,(2004) reported that fruits and vegetables after picking continue
to respire and as a result heat is produced, this heat is known as ‘vital
heat’, the amount which varies with particular amount of fruits and vegetables.
Vegetables
that respire more thereby generating most heat are those that perish/spoil most
rapidly (Wheeler, 2005). The resulting respiration of the fruits in addition to
the normal ripening process complicates an independent discussion on
microbiological spoilage of fruits in general and tomato in particular.
Fusarium
oxysporium f.sp.lycoperisici andVerticilliumalbo-atrumare two fungi that cause similar wilt disease
on tomato.(Nesmith etal.,1983). Fusarium is more common in replant
fields and gardens while Verticilliumhas
been destructive on greenhouse tomatoes and in commercial stake tomatoes. Verticillium wilt is more of a problem
at cooler temperature while Fusarium
wilt is considered a warm temperature disease. Both are favoured by wet
conditions.
According to Nesmithetal., (1983), both fungi are common inhabitants of Kentucky soils.
These fungi attack the plant through the roots and grow up through the
water-conducting vessels. FusariumandVerticilliummay be introduced to soils
in several ways: Old crop residues, transplants, wind, water,implement-borne
soils or mulches. These fungi become established readily in most soils and can
remain in the soil for years. When susceptible tomatoes are planted, in
infected soil, their roots are also subjected to attack by these fungi. Both
diseases are much more serious when accompanied by root knot nematode. These
problems can be controlled by using resistant tomato varieties and fumigating
or stream sterilizing greenhouse soils.
ABSTRACT
The
study examined the various fungal pathogens associated with tomatoes spoilage
as well as their preliminary taxonomic grouping up to genus level. 25 samples
of the spoiled tomatoes were collected from five locations within Gwagwalada
area council. Locations include: Passo Village, Gwagwalada market, Phase III,
New Kutunku and Dagiri. Thesame prevalence rate(100%) was recorded for all
tomato samples purchased in all locations.The level of awareness of the general
public in regards to the spoilage of tomatoes by Fungi was very significant
with about 62.5% of the respondents attesting to the claim of tomato spoilage
caused by Fungi and 37.5% disagreeing. Morphological studies reveal the fungal
members which include members of the genus Aspergillus,
Cladosporium, Fusarium, MucorPenicilliumand Rhizopus species. Species of Fusarium
were seen to be the most occurring in all samples. Satistical analysis also
concurred to the fact that fungi are responsible for spoilage of tomatoes
purchached in Gwagwalada (p< 0.05). It implies that fungi are greatly
responsible for tomato spoilage. Proper handling, transportation and thorough
washing with clean or chlorinated water will go a long way in reducing the risk
of tomato spoilage by Fungi.
Editor source: Isolation
And Characterization Of Fungi Associated With Spoiled Tomatoes In Gwagwalada