The effects of neem [Azadirachta indica A. Juss (meliaceae)] oil on Fusarium oxysporum f. sp. medicagenis and Fusarium subglutinans and the production of fusaric acid toxin

Marcia Regina Ferreira Geraldo,Carla Cristina Arroteia,Carlos Kemmelmeier

doi:10.4236/abb.2010.11001

Abstract

Fungi of the genus Fusarium are well known plant pathogens, cause several vascular diseases and are producers of toxins. In vitro assays evaluated the effects of Neem (Azadirachta indica) oil on the diameter of colonies, dry weight, spore production, spore viability and production of Fusaric Acid toxin on Fusarium oxysporum f. sp. medicagenis and Fusarium subglutinans isolates. Effects of Neem oil were analyzed at concentrations 0.25%, 0.5% and 1% in Czapek Yeast Agar medium. The production of Fu- saric acid was determined by Thin Layer Chromatography and quantified by UV spectrophotometry. Neem oil showed inhibitory effects on the isolates tested, although they varied according to type of isolate and oil concentration. Neem oil was efficient in reducing the colonies’ diameter and dry weight in concentration-dependent manner. Neem oil was efficacious at higher concentration in the decrease of sporulation. Spore germination was affected by Neem oil when the spore was grown in Neem-contained medium as when the spore emerged from a culture in a Neem medium. Neem oil decreased and even inhibited the production of Fusaric acid by the assayed isolates. Since these isolates are plant pathogens and producers of Fusaric acid, Neem oil may be introduced as an integral item in the management of host plants.

Highlights

Fungi of the genus Fusarium, known to be plant pathogens causing several vascular diseases, are largely distributed in soils, especially cultivated ones, and are active during the decomposition of cellulose material [1].Fusarium spp. is the main colonizer of pre-harvest cereal grains, even though it may occur in grain storage, especially under high humidity conditions [2]
In vitro assays evaluated the effects of Neem (Azadirachta indica) oil on the diameter of colonies, dry weight, spore production, spore viability and production of Fusaric Acid toxin on Fusarium oxysporum f. sp. medicagenis and Fusarium subglutinans isolates
Fusarium oxysporum f. sp. medicagenis is a important pathogen for alfafa (Medicago sativa L.), whereas Fusarium moniliforme f. sp. subglutinans = Fusarium subglutinans [3,4] is a pathogen for maize, sugarcane and other grasses.The above mentioned fungi are producers of mycotoxins with special reference to fusaric acid (5butylpicolinic acid), which has a hypotension effect in several animals due to an increase in dopamine in the brain and to other peripheral effects in the tryptophan metabolism [5,6]

Summary

INTRODUCTION

Fungi of the genus Fusarium, known to be plant pathogens causing several vascular diseases, are largely distributed in soils, especially cultivated ones, and are active during the decomposition of cellulose material [1]. Subglutinans = Fusarium subglutinans [3,4] is a pathogen for maize, sugarcane and other grasses.The above mentioned fungi are producers of mycotoxins with special reference to fusaric acid (5butylpicolinic acid), which has a hypotension effect in several animals due to an increase in dopamine in the brain and to other peripheral effects in the tryptophan metabolism [5,6]. Medicagenis and Fusarium subglutinans, due to the fact that if there is an inhibitory activity, the extract may be tested in host plants for the control of this pathogen. This is the main purpose of the present study

Fungal Isolates

Extraction and Quantification of FA

RESULTS AND DISCUSSION

CONCLUSIONS