Evaluation of the effective factors on contamination of pistachio yield to aflatoxin in orchard.

Some strains of Aspergillus flavus and Aspergillus parasiticus which belongs to molds, mainly, do production and excretion of aflatoxins. Meanwhile growth and development of these fungi on foodstuffs, produce this toxin which remains inside and outside of that. Spores of Aspergillus fungi are airborne and dispersed by air, simply. If the pistachio hull cracked early to due date (early split nuts) in orchard by insect or bird damage, fungus spore penetrate via ruptured hull and induce contamination while the least life conditions would be ready, especially, humidity. In generall, the hull prior to harvest would be intact, but sometimes prior to yield harvest, hull cracks together with shell in a limited number of fruits. Several probable factors are interferring in incidence of these kind of hull cracks. Current research was carried out in order to find the effective factors on contamination of pistachio yield to aflatoxin in orchard from 2001 to 2008 for 8 years. Field experiments were conducted in pistachio orchards of plantations of Kerman province and laboratory studies in IPRI that located in Rafsanjan. Results showed that total content of early split pistachios on Pistacia atlantica and P. mutica rootstocks were higher than P. vera rootstock. The highest content of aflatoxin observed on yield resulted from Pistacia atlantica and P. mutica rootstocks in compare to P. vera rootstock. The aflatoxin content of measured early split pistachios were much more higher than pistachios with irregular crackeh hulls. No aflatoxin were observed in pistachios with intact hulls. The lowest percentage of early splitting were observed in yield of pistachio trees with 10 and 20-years-oldand the highest percentage occurred in 30- years-old trees. The highest percentage of safe fruits obtained from the minimum trees intensity. The highest percentage of early splitting were observed in the maximum trees intensity. The percentage of stained fruits derived from trained trees were lower than non-trained trees. The long irrigation intervals (45 days) and deficit irrigation of pistachio trees from late April to early June increased substantially (untill 90%) early splitting occurrence in compare to control with regular irrigation, at harvest stage. Whatever the skipping in irrigation was closer to the final stages of growth season, the percentage of early splitting was reduced. The low concentrations of nutrient elements i.e. Ca, Fe and Mg in leafFe, Mn in hull and Ca in shell were appropriate indices for higher percentages of early splitting in pistachio. Furthermore, special characteristics of soil like, soil texture, structure, gypsum content, soil layering and percentage of gravels could be affecting on occurrence of early splitting. ١٧٦It seems soil salinity at least directly could not affect on increasing of early splitting. With consideration of the highest contamination of "Ahmadaghaei" and "Kalehghoochi", it was suggested an earlier harvest of these cultivars in compare to other cultivars. The appropriate time of harvest was suggested from the middle to end of September to avoid contamination of yield to aflatoxin and production of safe yield. The results revealed that Volk® (Mineral oil) 4% in compare to other treatments produced the highest amount of dried nuts and increased percentage of nut splitting. Volk® (Mineral oil) with higher concentrations (6 and 8 %) in compare to other treatments increased soft hull cracking percentage, dried hull cracking percentage, soft early splitting percentage and dried early splitting percentage. The early splitting percentage, irregular hull cracking percentage and the contents of yield contamination to B1 and total aflatoxin in Kerman area showed the highest level and in two other areas (Rafsanjan and Anar) with this order contained the lowest content. It was concluded that the yield content could be effective on occurrence of early splitting, but would not on irregular hull cracks.