SCREENING OF TOMATO ACCESSIONS FOR RESISTANCE TO ...

Due to the growth of the fungus within the plant's vascular tissue, the plant's water supply is greatly
affected. This lack of water induces the leaves' stomata to close, the leaves wilt, and the plant
eventually dies. It is at this point that the fungus invades the plant's parenchymatous
tissue, until it
finally reaches the surface of the dead tissue, where it sporulates abundantly (Agrios, 1988). The
resulting spores can then be used as new inoculums for further spread of the fungus
Due to prolonged survival in soil as a saprophyte and as resistant structures, F
oxysporum is difficult to control (Mujeebur and Shahana, 2002; Borrero et al., 2004). Among control
strategies available for Fusarium wilt management, soil fumigation and use of resistant cultivars are
the most used. Biological control of plant pathogens using antagonistic
fungal and bacterial strains is
gaining increasing importance. Soil has untapped potential and contains several potential biocontrol
agents (BCAs) such as Pseudomonas spp., Trichoderma spp. and non-pathogenic Fusarium spp. that
have shown high antagonistic activity against several soil-borne pathogens (Fuchs et al., 1999;
Ramamoorthy et aI., 2001). So far, several bacterial and fungal antagonistic strains have been shown
to reduce the damage caused by different pathogens, including F oxysporum f. sp. Iycopersici
(Postma and Rattink, 1992; Alabouvette, 200 I; Moretti et al., 2008).
The best recommended
way to control the disease is selecting resistant varieties of tomato (Silva and
Bettiol, 2005). Recently there have been many reports about using bioactive compounds from
biological control agents which were extracted from different fungi that inhibit many plant
pathogenic fungi, including Fusarium wilt of tomato (Soytong, 1992). These bioactive compounds
are Tricotoxin A50 extracted from Trichoderma harzianum PCO1; and Chaetoglobosin C extracted