EVALUATION OF THE FUNGICIDAL ACTIVITY OF LEAVES POWDERS AND EXTRACTS OF FIFTEEN MEXICAN PLANTS AGAINST FUSARIUM OXYSPORUM F.SP. GADIOLI (MASSEY) SNYDER AND HANSEN.

Abstract

Fusarium oxysporum f. sp. gladioli represent one of the problems of greater importance in the culture of gladiolus. The resistance of this fungus to the fungicides has stimulated the search of new alternatives control measures. The natural plant extracts used in the study were safer to the environment and effective in the control of the plant pathogen tested. The present paper describes the in vitro fungicidal or fungistatic effect of powders (20 mg mL-1) and of aqueou, methanol and hexane extracts (5%) of 15 plant species on the development of F. oxysporum f. sp. gladioli on artificial growth media and volatile compound identification. Twelve plant species showed antifungal activity. The hexane extract of Chenopodium ambrosioides (by its fungicidal activity), the methanol extract with Spondias purpurea and Psidium guajava, as well as the aqueous extract of L. esculenta and Guazuma ulmifolia inhibited the mycelia growth with a percentage superior to 50%. Also, the powders of Byrsonima crassifolia diminished the percentage germination and sporulation of the pathogen. All the species presented antifungal activity in form of methanol extract. The 80% of the plant powders increased the rate of mycelial growth of the fungus. By chromatography of gases and spectrometry of masses, 90 volatile compounds in the powders and extracts were identified that showed activity on the fungus. The majority of the compounds were fatty acids (18.8%), monoterpenes (4.2%), sesquiterpenes (23.6%) and phenolic compound (6.3%). The high chemical diversity of the analyzed plant species, differentially affected the development of the fungus, either for the individual compounds or for synergism of some of them.