In-vitro Evaluation of Antagonists and Fungicides in Controlling Citrus Gummosis Caused by Phytophthora, Phytopythium and Pythium species in Tunisia

Abstract

Aims: This study investigated the efficiency of some bioagents and fungicides against causals agents of gummosis of citrus. Study Design: Antifungal activities of bioagents and effect of fungicides. Place and Duration of Study: Department of Biological Sciences and Plant Protection, Higher Institute of Agronomy of Chott Mariem, 4042, Sousse, Tunisia, between June 2015 and July 2015. Methodology: Antifungal activity was carried out using dual culture and sandwich plate methods. Antibacterial activity was carried out using bacterial suspension; while fungicide effect was carried out using food poisoned technique. The mycoparasitim of fungal antagonists was also determined. Results: The tested bioagents and fungicides showed significantly effect on mycelial growth inhibition of the pathogens compared to the control. In the dual culture assay, the highest percent of the mycelia growth inhibition (90%) was obtained by T. viride and T. harzianum. However, P. digitatum and P. italicum revealed to be the least effective with, respectively, 70% and 60% of growth inhibition. The effect of volatile substances of these bioagents showed also that T. viride exhibited the highest percent of inhibition (85%), followed by T. harzianum (75%), P. digitatum (60%) and P. italicum (50%). The mycoparasitim was also noted. Bacillus isolates were found significantly effective in reducing the mycelial growth of the Oomycotaspecies, with a percent of mycelium inhibition verging from 95% to 54%. However, copper fungicides generated the highest percent of the mycelial growth inhibition (100%), following by the acid citric and borax fungicides which recorded a percent of the mycelial growth inhibition of 10.82% and 12.93%, respectively. Conclusion: Thus the study indicated that the integration of bioagents can provide a better management of the gummosis of citrus.