In recent decades, spring frost considered a serious threat in pistachio production (Pistacia vera). Considering that, Iran is one of the most important centers of pistachio production and has the highest variety of pistachios in the world, the identification of domestic and wild different rootstocks and their crosses to reach cold-tolerant rootstocks could be one of the effective solutions to face the challenge of spring frost. In this study, cold tolerance was assessed in fourteen rootstocks of pistachio domestic species (Badami Zarand, Sarakhs and Qazvini), interspecific hybrids (Qazvini×Khinjuk, Qazvini×Mutica, Qazvini × Baneh Baghi, Qazvini × Atlantica, Qazvini× Integerrima), non-domesticated species (Atlantica (P. atlantica), Integerrima, Khinjuk, Sarakhs, Mutica (P. atlantica sub. mutica) and Baneh Baghi (P. mutica × P. vera)) and UCB1 hybrid rootstock at low temperatures (4, 0 and -4 °C) for 2 hours. This experiment was conducted in a factorial completely randomized design with three replications on one-year-old seedlings in greenhouse conditions. The results showed that the rate of ion leakage, malondialdehyde and injury index percentage was significant (p <0.01) and their values were decreased in the cold-tolerant rootstocks than the cold-sensitive rootstocks. The interaction between treatments showed that the temperature of - 4 °C caused a significant reduction in ion leakage and malondialdehyde in the cold-tolerant rootstocks. Proline was increased in the cold-tolerant rootstocks compare to cold-sensitive rootstocks. The results of cation leakage percentage were significant in temperature and rootstocks (p <0.01). The results showed that the highest percentage of cation leakage related to potassium and there was a positive and significant correlation between calcium and magnesium and cell membrane stability. According to the results, the most sensitive rootstock was UCB1, Integerrima, Khinjuk and Baneh Baghi, respectively. Hybrids Qazvini , Baneh Baghi, Khinjuk and Integerrima rootstocks were significantly reduced under low-temperature stress. Mutica, Qazvini×Mutica, Sarakhs, Qazvini, Qazvini×Atlantica rootstocks, improved physiological and biochemical traits and maintained cell membrane integrity and finally showed greater tolerance to frost and freezing temperatures, which can be considered in the breeding program. Manuscript profile

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. Manuscript profile

Population density of Aspergillus section Flavi in pistachio kernels of Iranian cultivars was studied in main pistachio growing areas of Iran during 2015 to 2017. In order to investigate the rate of contamination of pistachio cultivars to Aspergillus section Flavi and aflatoxins, 13 pistachio cultivars, including Akbari, Kaleh-ghouchi, Ovhadi, Ahmad-aghaee, Momtaz, Italian pistachio, Shahpasand, Pesteh-e-ghermes, Pesteh-e-garmeh, Ghazvini, Abbasali and Khanjari were selected from different parts of Semnan, Khorosan Razavi and Kerman provinces. A total of 125 samples of pistachio kernels were collected from different cultivars of pistachio trees in orchards. The samples were cultured on AFPA using serial dilution method. After 3 to 7 days, the plates were examined and isolates of Aspergillus section Flavi were identified and relative densities of them were recorded. The values ranged from 1.6×103 to 1.6×104 CFU/g in pistachio samples.The statistical analysis showed that the population density of Aspergillus section Flavi was varied with the type of cultivars. The results indicated that among tested cultivars, Akbari showed the least and Shahpasand the most population density of Aspergillus section Flavi among pistachio cultivars, respectively. The aflatoxins content of pistachio samples were extracted and analysed through Thin Layer Chromatography (TLC) and flurodensitometer. There were Significant differences among different cultivars in the contamination of pistachio kernels to Aspergillus section Flavi and aflatoxin. (α =5%). It was observed that Akbari had the least whereas Shahpasand had the greatest amount of aflatoxin production, respectively. Manuscript profile

Aflatoxin is an important fungal contaminant in various crops. The substrate and its compounds are involved in the growth of fungus and the production of toxins. In order to investigate correlation between sugar and lipid content as the major chemical composition of pistachio kernels with Aspergillus flavus growth and aflatoxin production, the total sugar content was extracted by phenol-sulphoric method and estimated by spectrophotometry. The lipid was also extracted by Soxhlet method. A toxigenic A. flavus strain was used for the study of the fungal growth and aflatoxin B1 production. For that, 20 gram of kernels of different pistachio cultivars were inoculated with 1 ml of fungal spore suspension (2×106 spores/ml) in a completely randomized design with three replications. Eight days after inoculation, the average percent of fungal growth and colonization of A. flavus were calculated. The aflatoxin produced in inoculated pistachios was extracted by Best Foods (BF) method and measured by thin layer chromatography (TLC). The results showed that there was no significant difference in the amount of sugar content in different cultivars of pistachios kernel but the amount of total lipid content was different (P≤0.05). Results of statistical analysis showed that there was no significant correlation between sugar content with fungal growth and aflatoxin production in pistachio cultivars as well as lipid percentage and aflatoxin B1 production. Therefore, to find sources of resistance to A. flavus in commercial pistachio cultivars in aflatoxin management programs, these two factors cannot be used as a standard scale of resistance. Manuscript profile

Inoculations of plant roots with arbuscular mycorrhizae can reduce Verticillium wilt severity. In present research, the effect of inoculation of Verticillium dahliae (Vd) and three species of arbuscular mycorrhizae (AM), Funneliformis mosseae, Rhizophagus irregularis and Claroideoglomus tunicate were studied on the activity of catalase, peroxidase, superoxide dismutase and phenylalanine ammonia-lyase in the root of Ahmad Aghaei and Badami Zarand pistachio rootstocks. The roots of the pistachio seedlings were inoculated with 100 propagules per gram of three species arbuscular mycorrhizae and two months later, Verticillium dahliae was inoculated. Measurement of enzyme activity was done after V. dahliae inoculation at 11 different times. The experiment was conducted as a factorial in a completely randomized design with 5 replications. The results showed that in Vd treatment, the specific activity of enzymes in Ahmad Aghaei decreased after an increasing period in days 8 to 12 after vd inoculation, then decreased less than AM inoculations, but in Badami Zarand, the activity of enzymes increased in a (days 8-16) and after that, despite the decreasing trend, it was still higher than AM treatment. In AM+Vd treatment, enzyme activity increased faster in both pistachio rootstocks compared to other treatments. In Badami Zarand, the time of the enzymes, peak activity was longer than in Ahmad Aghaei rootstocks. In general, the results of the present research indicated that increasing antioxidant enzyme activity can reduce the severity of Verticillium wilt in pistachio seedlings. Manuscript profile

Pistachio is one of the economically important horticultural crops in Iran. The main pistachio-producing areas in Iran are located at the edge of the desert and are affected by soil and water salinity. Water and nutrient uptake by the root decreases under saline conditions. In this study, the effects of foliar growth regulators applied at different times on the nutrient uptake and leaf nutrient content of pistachio trees were examined in accordance with a split-plot experimental design based on a randomized complete block design with three replications. The field experiment was conducted with a group of 30-year-old pistachio trees that have been exposed to water and soil salinity. Experimental factors included the timing of foliar application and the applied concentrations of plant growth regulators. The timing of foliar application was the main factor and was split into three levels: application on May 21th, June 21th, and May 21th + June 21th. Different concentrations of plant growth regulators, including sodium nitroprusside, salicylic acid, and jasmonic acid, were split into ten levels and were designated as the sub-factor. Results showed that the timing of application and the applied concentration of plant growth regulators affected root nutrient uptake and leaf nutrient content. The one-time application of plant growth regulators in June and the two-stage application of plant growth regulators in May and June resulted in the highest increase in leaf nutrient content compared with the control treatment. The application of low and moderate concentrations of plant growth regulators increased leaf nutrient content compared with the control treatment. High concentrations of plant growth regulators exerted no significant effects on leaf nutrient content. Manuscript profile

Understanding the function of Trichoderma species in the control of Phytophthora drechsleri in pistachio orchards is very important. In this study, the effects of liquid extra-cellular secretions and volatile compounds secreted by 27 isolates of Trichoderma harzianum, T. crassum, T. koningii, T.aureoviride, T. asperellum, T. brevicompactum, T.longibrachiatum and T. virens were investigated on Phytophthora drechsleri growth and zoospore production. Due to cell wall combination of P. drechsleri, the ability of Trichoderma isolates in the production of β-1,3 glucanase and cellulase was evaluated in media with different carbon sources. The inhibitory effects of the 16 isolates of Trichoderma from growth of P. drechsleri were examined in a dual culture test. The results showed that Trichoderma isolates had a variable effect on the growth and zoospore production of P. drechsleri. Trichoderma harzianum-136 and T. harzianum-8279 revealed the highest inhibitory effect on radial growth of P. drechsleri in 20 and 30 percent concentrations of liquid extra-cellular secretions, respectively. Both isolates also showed the highest inhibitory effect on zoospore production of P. drechsleri in 10 percent concentration of extra-cellular liquid secretions. In the volatile compounds test, T. harzianum-8279 had the highest effect on the growth of P. drechsleri. In all Trichoderma isolates, the activity of β-1,3 glucanase was higher than cellulase activity. The enzyme production was also higher in the liquid medium containing the cell wall of P. drechsleri compared to glycerol as a carbon source. The highest activity of β-1,3 glucanase and cellulase was observed in T. harzianum-8279. Manuscript profile