the effect of testa on reduction of aspergillus flavus growth and aflatoxin b1 production in pistachio kernels of different cultivars

abstract in order to evaluate the effect of testa on reduction of fungal growth and aflatoxin b1 producthon, ten cultivars of pistachio were collected from different parts of pistachio belt i-e rafsanjan, damghan and ghazvin of iran. a section of testa and one mm of endosperm were scraped. 20 gr. of wounded kernels and 20 gr. of unwounded kernels were surface sterilized and then placed in petri dishes separately (completely randomized design in 3 replications). one ml of the spore suspension of aflatoxigenic aspergillus flavus was added to each petri dish. (spore suspension was adjusted to contain 2×106 spore per ml ). the plates were placed over water in plastic boxes and these were then placed in an incubator at 26ºc for 2.5, 5 and 8 days. after inoculation, growth rate and colonization of a. flavus on wounded and unwounded pistachio kernels in different cultivars were measured. also aflatoxin content of inoculated kernels was extracted by bf method and estimated by tlc and densitometer. average of a. flavus growth percentage on surface of wounded and unwounded kernels was compared with t-student test. the results of this research indicated a significant difference in fungus growth rate and aflatoxin b1 production between wounded and unwounded kernels of pistachio cultivars. in other words, testa in unwounded kernels could be considered as a resistant barrier against the fungus penetration into kernels and reduced a. flavus growth and aflatoxin b1 production as compared with wounded kernels.