Effect of Sulfur on Toxigenic Aspergillus flavus In Vitro

Application of sulfur to control the common pistachio psylla has been nowadays popular. The psylla is one of the main pistachios’ pests. Aspergillus flavus, the most important aflatoxin producer, has a strong impact in the mycoflora of pistachio orchards. The present study has been conducted to determine the effects of sulfur on A. flavus. Therefore, a toxigenic A. flavus strain was cultured on potato dextrose agar (PDA) medium, and the effects of mineral sulfur, refinery sulfur and sodium metabisulfite were closely monitored on fungal mycelial dry weight, germination of spores, germ tube and mycelium germination. The Fungal parameters measurement for sulfur vapor exposure and sulfur addition to the culture medium declared no significant effect on the growth of A. flavus mycelium in the direct addition. But sulfur in liquid medium as well as in high concentrations caused mycelial dry weight loss. Importantly, the sublimation of 0, 0.5, 1, 2, 5, 10, 25 and 50 gm-3 from the refinery sulfur, prevented completely the growth of germinated spores and mycelial. Significantly, the complete inhibition of spore germination was observed at a concentration level of 2 g m-3 and also sodium metabisulfite prevented the growth of A. flavus at a concentration of 15 g l-1 culture medium. The sulfur usage in culture medium declared no inhibition of A. flavus growth, but at high concentrations in liquid medium, it reduced mycelial dry weight. Therefore, it is found that the sulfur application in any kind to control of psylla would not probably effect significantly on the aflatoxigenic A. flavus.