International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

THE FUNGAL PHYTOTOXINS AND THEIR POTENTIAL ROLE AS HERBICIDES IN INTEGRATED
CONTROL METHODS AGAINST WEEDS.
Antonio Evidente
Dipartimento di Scienze del Suolo, della Pianta e dell’Ambiente, Università di Napoli Federico II, Via Università 100,
80055 Portici
The man weed battle started long time ago due to the great hazard resulted from their wide diffusion in
agricultural crops and pastures. Weeds have created heavy problems in reforestation activities and in important
economical infrastructures. In the last 50 years, beside the traditional agrarian practises, the most diffused methods in
controlling weeds are the use of chemical herbicides which are responsible for major environmental pollution with
human and animal health risks.
Therefore, numerous studies have been carried out to develop biological control using natural weed enemies as
insects, viruses, bacteria and fungi but a particular interest has been directed towards phytopathogenic fungi which are
the most common plant pathogens that in respect to other microorganisms may be applied with safety and simplicity.
Phytopathogenic fungi are responsible, together with other microbial agents, of severe damages to important
agrarian forestall and ornamental plants Frequently, these fungal species produce phytotoxins, bioactive metabolites
with different chemical structure, mode of action, host specificity, biological activity and environmental impact. Toxins
are generally substances which interfere with plant metabolism of which many are directly responsible of pathogenesis
while others are not considered toxins at all 1,2 .
Studies conducted in the last years have concentrated on controlling weed diffusion in important agrarian crops.
Fungal pathogens isolated from some infected tissue of weeds are generally belonging to important taxonomic genera
(Alternaria, Ascochyta, Drechslera, Fusarium, Melanconis, Phoma, Pyrenophora ). Some phytotoxins were isolated and
characterised to determine their role in developing new methods for weed control, Their direct application or that of
their derivatives or/and analogues with the pathogen may increase the herbicidal activity so improving the efficacy in
terms of pathogenesis, virulence and herbicidal selectivity
Structure elucidation and stereochemistry of phytotoxins may allow to plan their total enantioselective
synthesis in order to obtain amounts suitable to carry out experiments in green houses and in fields to develop strategies
for the biological integrated management of weeds. Some toxins may be derivatised to modulate their biological activity
in terms of phytotoxicity and selectivity and to obtain new natural safe herbicides.
Furthermore, phytotoxins can be used to develop a method for their analysis in complex samples. Therefore, if
the phytotoxins are virulence features they may be used as biomarkers for in vitro selection of the best fungal strain to
be used in the integrated management methods. In this communication, a brief overview will be presented on the results
obtained on developing strategies to biologically control of Chenopodium album, Striga hermonthica and Orobanche
ramosa, infesting many important agrarian crops like maize, beet root, millet, sorghum, sunflower, tomato, legumes,
etc 2,3 .
References
1. Ballio, A.; Graniti, A. Experientia, 1991, 47, 751-826.
2. Evidente, A.; Motta, A Phytotoxins from fungi, pathogenic for agrarian, forestal and weedy plants. In Bioactive
Compounds from Natural Sources, Tringali, C. (Ed.), Taylor & Francis, London, 2001. Chapter 12, pp. 473-525.
3. Evidente, A.; Abouzeid, M.A. Characterization of Phytotoxins from Phytopathogenic Fungi and their Potential Use
as Herbicides in Integrated Crop Management. In Handbook of Sustainable Weed Management, Harminder, P.S.
(Ed.), The Haworth Press Inc., Binghamton, NY, USA (2002) in press.
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