Articles
VARIABILITY IN AFLATOXICOGENIC POTENTIAL AND SCLOROTIAL PRODUCTION OF A. FLAVUS IN PISTACHIO IN IRAN
Article number
726_106
Pages
619 – 626
Language
English
Abstract
The variability in sclerotial production and toxigenic potential of Aspergillus flavus in pistachio nuts in Iran, was studied by isolating 200 A. flavus isolates from major pistachio growing regions in Rafsanjan, Zarand, Kerman, Noogh, Sirjan and Damghan in Kerman and Semnan provinces: 122 isolates were from pistachio nuts from 51 different storages and terminals; 63 isolates from soil samples collected during July to October at a 15-days interval in four different locations; and the rest were airborne A. flavus was captured by exposing AFPA media plates for 10 min at 50 cm above ground in pistachio orchards.
A pure culture of each isolate was established from a single spore and maintained on PDA and Czapek media.
Culture pattern, sporulation and sclerotial production of each isolate at 25±1 °C was recorded after 10-15 days: 42% of isolates from soil, 33% isolates from the airborne fungi and 27% isolates from pistachio nuts could produce sclerotia.
Rate of sclerotia production varied among various groups of A. flavus isolates, but no significant variation was observed within the group even after successive sub-culturing for 5 months.
Based on rate of scleortia production A. flavus isolates were categorized into three groups.
From each group seven representative isolates were selected and their toxigenic potential was estimated by inoculating spore suspension (4´106 spores mL-1) to 20 g of pistachio nuts and incubated at 25± 1°C for 8 days.
Aflatoxin (Af B1) concentration in the inoculated nuts estimated by enzyme-linked immunosorbent assay (ELISA) ranged between 0-5034.3 ppb.
High correlation (r = 95%) was observed between sclerotia production and aflatoxin concentration.
Isolates that produced less sclerotia had low aflatoxin levels and isolates that produced more sclerotia could produce high amount of aflatoxin.
This study showed that not all isolates of A. flavus infecting pistachio produce sclerotia and there is variability in rate of scleortia production, which in turn was directly proportional to the toxigenic potential of an isolate.
Further study exploring the relationship between sclerotia production and toxigenic potential could lead to the development of a simple assay for the identification of toxigenic strains of A. flavus.
A pure culture of each isolate was established from a single spore and maintained on PDA and Czapek media.
Culture pattern, sporulation and sclerotial production of each isolate at 25±1 °C was recorded after 10-15 days: 42% of isolates from soil, 33% isolates from the airborne fungi and 27% isolates from pistachio nuts could produce sclerotia.
Rate of sclerotia production varied among various groups of A. flavus isolates, but no significant variation was observed within the group even after successive sub-culturing for 5 months.
Based on rate of scleortia production A. flavus isolates were categorized into three groups.
From each group seven representative isolates were selected and their toxigenic potential was estimated by inoculating spore suspension (4´106 spores mL-1) to 20 g of pistachio nuts and incubated at 25± 1°C for 8 days.
Aflatoxin (Af B1) concentration in the inoculated nuts estimated by enzyme-linked immunosorbent assay (ELISA) ranged between 0-5034.3 ppb.
High correlation (r = 95%) was observed between sclerotia production and aflatoxin concentration.
Isolates that produced less sclerotia had low aflatoxin levels and isolates that produced more sclerotia could produce high amount of aflatoxin.
This study showed that not all isolates of A. flavus infecting pistachio produce sclerotia and there is variability in rate of scleortia production, which in turn was directly proportional to the toxigenic potential of an isolate.
Further study exploring the relationship between sclerotia production and toxigenic potential could lead to the development of a simple assay for the identification of toxigenic strains of A. flavus.
Authors
M. Mirabolfathy, M.M. Ghadarijani, F. Waliyar
Keywords
sclerotia, aflatoxinB1
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