جستجوی مقالات مرتبط با کلیدواژه « mycotoxin » در نشریات گروه « گیاهپزشکی »

Fusarium verticillioides is one of the most important and potent fungi producing fumonisins and causes major damage to agricultural products and adverse health effects on comcumers. The production of these toxins is greatly influenced by environmental factors. In this study, the effect of environmental factors, including light duration (0, 12 and 24 h), seed moisture content (15, 18, 25, 23, 25, 28 and 30%) and pH (4, 5, 6 and 7) were evaluated on fumonisin B1 production. Towards this aim, fungal isolates were recovered from corn fields showing signs and symptoms of infection and were subjected to morphological identifiction. Fumonisin B1 was extracted using acetonitrile, methanol, cationic resin, alumina carbon, and then detected by TLC and HPLC methodes.The identity of the isolates was determined as F. verticillioides. The results of HPLC analysis showed that the amount of fumonisin B1 produced by F. verticillioides in different treatments ranged from 200 ng/ml to 520 ng/ml. The highests amount of fumonisin B1 including 424 ng/ml, 422 ng/ml and 520 ng/ml were produced in 28% corn seed moister pH: 4 and 24 hours-light treatment, respectively. Therefore, by controlling the environmental conditions in seed storage and silo, the production of fumonisins can be minimized.

The use of nontoxigenic strains of Aspergillus flavus as an effective biological method to reduce aflatoxin is being developed in different countries. Nontoxigenic strains are able to compete with toxigenic strains by substrate occupation, which reduces the toxigenic population and the amount of aflatoxin in the substrate. The aim of study was to investigate the morphological diversity in the nontoxigenic population of A. flavus. To isolate nontoxigenic strains from 225 fruit and pistachio soil samples obtained from different provinces, AFPA culture medium and dilution series method were used. Primary nontoxigenicity screening was performed by ammonia vapor method in coconut agar medium and thin layer chromatography was used for result confirmation. Isolates were identified molecularly using FLAVIQ1/FlaQ2 species-specific primers. In order to identify the macromorphological and micromorphological features of 56 obtained strains, four culture media including CYA (Czapek yeast agar), MEA (malt extract agar), CY20S (Czapek yeast 20% sucrose) and CZ (Czapek) were used. Investigation of macro-micromorphological features, classified A. flavus strains into five groups. Colony growth pattern on CYA25 cultural media has shown good differentiation between isolates. The results showed that there is a great variety among nontoxigenic A. flavus isolates obtained from different agro ecological zones due to the presence of different species in the A. flavus complex.

Single strand DNA or RNA known as aptamers, are able to detect the target molecule with specificity at the monoclonal antibody level. However, the placement of mycotoxins in small molecule groups and their high molecular weight differences with aptamers have become a serious challenge in introducing aptameric probes for them. In the present study, in order to achieve a new and shorter aptamers sequence for aflatoxin B1 (AFB1), an initial oligonucleotide library (Lib1) was designed based on the sequence of a known AFB1 aptamer (named Apt1, 50 bp) using the genetic algorithm. The best aptamer from the Lib1 library was selected based on the molecular docking results and has been modified to create a new library (Lib2) using the truncating strategy. Virtual screening of the Lib2 library in terms of their binding affinity over AFB1 molecule led to obtain the truncated aptamer, C52-T, with 19 bp in length. Type of interaction and stability of C52-T-AFB1 complex were investigated using molecular dynamics simulations (MD) and MM-PBSA method. The affinity constant of C52, C52-T and Apt1 aptamers over AFB1 were estimated through unmodified gold nanoparticle-based colorimetric assay. The experimentally founding and in silico results were completely consistent. It seems that the computational techniques have the great potential to introduce sensitive molecular probes to design specific mycotoxins aptasensors.

Aflatoxin contamination of pistachio nut is a health challenge that can affect the economic value of the largest Iranian non-oil exports. This potent hepatocarcinogen mycotoxin is produced by some species of Aspergillus, particularly by A. flavus, under certain conditions during fruiting, harvesting, transportation and storage. Infection of pistachio to the fungus in the orchard is the key factor in its contamination with aflatoxin. This situation occurs with the formation of early splited pistachios and mechanical damages that caused by biotic and abiotic factors. The environmental temperature and relative humidity and the moisture content of pistachio, during the different stages of pistachio production and processing, have significant roles in the incidence and distribution of fungal contamination as well as the increasing of aflatoxin production. The inhibition of these factors is possible with applying of some agronomic, mechanical, physical and biological methods. Orchard establishment based on principles of gardening like optimal plant spacing, uniformity of cultivars, good pruning, proper irrigation method and nutrition along with on time harvesting, proper processing and storage, can guarantee the production of a healthy and valuable product. Biological controls using nontoxinogenic strains of A. flavus and yeasts are also recorded as successful strategies for reducing the pistachio aflatoxin.

Madder is one of the most important crops that used for medical and industrial applications and is widely cultivated in Yazd province. During 2012, sampling was done form seeds madder in important areas planted in Yazd province, including Bafq and Ardakan. After culturing and purification of fungal isolates in PDA and CLA media, additional identification was performed by PCR with specific primers for each species. Detection of fungi mycotoxins producing potential such as Nivalenol (NIV) using Tri13 primers was done. High-performance liquid chromatography (HPLC) was used to confirm the produce NIV mycotoxins potential in Fusarium species. 249 fungal strains were isolated from madder seed belonging to 6 genera of fungi including Fusarium spp., Aspergillus spp., Penicillium spp., Alternaria spp., Rhizoctonia solani and Rhizpous spp., that Fusarium isolates with 71 percent was the most frequency among fungi isolated. Among Fusarium fungi isolated, F. solani (55 isolates) and F. oxysporum (41 isolates) were the most frequency. F. poae, F. semitectum and F. equiseti ability to produce mycotoxins such as Nivalenol (NIV) that are harmful to human health and animals as well as effect on the quantity and quality of madder color production. Tri13 gene involved in production NIV was detected in three Fusarium species that all isolates produce NIV. The results of HPLC showed that all studied Fusarium fungi, have the potential to produce NIV mycotoxins. The results of this study showed that fungi associated with seeds madder are able to produce trichothecene mycotoxins that they can be dangerous for consumers. Given that, this is the first report of fungi mycotoxins producing on seeds madder in Yazd province, thus should be measures to control and reduce fungal agents in these products.

Several species of the genus Aspergillus including Aspergillus niger and its segregates are involved in bunch rots of grapevine as well as contamination of grapevine products worldwide. These fungal agents reduce both yield and quality of grape and its products by damaging and destroying the berries and the production and accumulation of ochratoxin A. This study was carried out in 2011 and 2012 in order to characterize black aspergilli species on grape and raisin in southern regions of East and West Azerbaijan provinces including Azarshar، Bonab، Ajabshir، Maragheh، Malekan and Miyandoab counties. The isolation and purification of fungal isolates was performed with commonly used methods in plant pathology. A total number of 167 Aspergillus isolates were recovered from 231 grape and raisin samples. Based on morphological characteristics، all of the isolates were identified as members of A. niger species complex. Sequence data for the β- tubulin gene were generated for the representative isolates for each geographical region. Based on the sequence data from β- tubulin gene، the identity of the isolates was determined as A. tubingensis (94%)، A. niger (3. 6%)، A. welwitschiae (1. 2%) and A. uvarum (1. 2%). This study provides the first report on the occurrence of A. uvarum on grape from Iran and first report on the occurrence A. welwitschiae on grape in the world. With the identification of Aspergilllus spp. occurring of grapevines and its products in this region، it will be possible to further actions in monitoring the production and accumulation of ochratoxin A in grape vines products.