Effect of Irrigation Systems on the Contamination of Aspergillus flavus and Aflatoxin Production in Shahpasand Pistachio Cultivar

Aflatoxins are secondary metabolites produced by Aspergillus flavus, A. parasiticus, A. tamari, A. bombycis and A. nomius species. Relative humidity (RH) is one of the most important parameters influencing the development of aflatoxins in pistachio orchards by Aspergillus species. The type of irrigation system affects density and frequency of the Aspergillus species in the soil. In the current study, to evaluate fungus population density three irrigation treatments (flood, drip-surface, and subsurface irrigation) were applied. In order to investigate the population density of Aspergillus flavus in different irrigation systems, sampling was done from soil and kernels of Shahpasand cultivar at Damghan's Pistachio Research Station under various types of irrigation systems implementation. The samples were inoculated on AFPA medium using serial dilution method. The results indicated that the population density of A. flavus ranged various in pistachio kernels and soils between different types of irrigation system. Through subsurface irrigation, the population density of fungal colonies was significantly at the lowest level. The results showed that the use of modified adopted subsurface irrigation system had been effective in reducing soil surface moisture and led to decrease of population density in comparison with the conventional surface drip irrigation.