Abstract

Antagonistic activity of 24 selected bacterial strains detected by previous microbiological studies to Aspergillus flavus was tested in vitro and in vivoconditions. Within 24 strains, only ten strains showed remarkable inhibition zone (6-34 mm) against the pathogen in assays carried out in Petri plates. Both cell suspension and culture filtrates of prominent 10 bacterial strains were also tested in order to control A. flavus on lemon fruits cvs Meyer and Interdonato under storage conditions. The cell suspension of nine strains and the culture filtrates of three strains led to suppression on disease development on lemon fruits. The highest control was obtained by the cell suspension of Pantoea agglomerans RK-153.Erwinia chrysanthemi RK-67 and Bacillus subtilis RK-6 treatments reduced disease severity on both lemon cultivars. Furthermore, both the cell suspension and culture filtrates of Burkholderia cepacia strain RK-277 reduced disease severity on only cvs Interdonato, but not on Meyer. There was no significant difference in decay diameters among those treatments, compared to the negative control at 35 days of inoculation. Even other tested strains also slightly reduced disease severity compared to strains determined as efficient ones; disease severity resulted from other strains were statistically significant, compared to negative control. In conclusion, these strains can be used as new biocontrol agents in controlling postharvest decay of citrus fruit.

Key words: Antibiosis, Aspergillus flavus biocontrol, citrus disease, lemon,Pantoea agglomerans, postharvest.