فصلنامه بیماریهای گیاهی
سال پنجاه و ششم شماره 1 (بهار 1399)

Pierce's disease (PD) has been recently reported of Iran. To determine the distribution pattern of this disease, during 2013-2018 years, 365 samples of leaf and stem of grapes of 88 vineyards were collected with PD symptoms. Samples obtained of Iranian grape growing provinces of Fars, Khorasan Razavi, North Khorasan, South Khorasan, Semnan, Alborz, Tehran, Qazvin, Zanjan, West Azarbaijan, East Azarbaijan, Kurdistan, Kermanshah, Lorestan, Kohgiluyeh va BoyerAhmad, Markazi, Hamedan and Chahar Mahal va Bakhtiary. Samples were tested for the presence of Xylella fastidiosa by culturing, DAS-ELISA and PCR assay with X. fastidiosa-specific primers. Pathogenicity tests, for some isolates, were conducted on grapevine (cv. Bidaneh Qazvin) under greenhouse conditions. Early symptoms is leaf scorched, while adjacent tissues turned yellow or red. Some grapes showed “matchstick” symptoms in which the leaves dropped from the plant, while petioles remained attached. Approximately 56%, 44.8% and 7.1% of the samples, by DAS-ELISA, PCR and culturing, were infected to X. fastidiosa, respectively. Although based on DAS-ELISA all of the sampled provinces showed infected to X. fastidiosa, there were by the results of culturing and PCR infected to X. fastidiosa is definitive for some vineyards provinces of Fars, Khorasan Razavi, Alborz, Qazvin, Zanjan, Lorestan, Hamedan and Chahar Mahal-va-Bakhtiary. This mapping obtained the dispersion of PD in vineyards of Iran, and can be used as a distribution guide map of X. fastidiosa for plant protection organization of Iran.

Melon (Cucumis melo) which belongs to the family Cucurbitaceae, is one of most important plants, cultivated in different regions of Iran. In a field survey in Guilan province, the widespread distribution of leaf spot symptoms on melon was observed. In order to identify the fungal agents associated with this disease, symptomatic leaves were collected from the field and taken to the laboratory. Single spore cultures derived directly from leaf spots. In total, 45 isolates were obtained of which 16 were identified based on sequences of five genomic loci (ITS, ACT, tef1, cmdA and his3), host plants, and morphological data. The results of five-gene phylogenetic analysis have revealed that, of the 16 isolates, four isolates were identified as Cercospora sp. G and the remaining 12 isolates nested within Cercospora cf. flagellaris. To our knowledge, this is the first report of the Cercospora sp. G and Cercospora cf. flagellaris on Cucumis melo in the world. Moreover, it is the first report of Cercospora leaf spot (CLS) on Cucumis melo in Iran.

Bacterial blotch is one of the most important diseases of white button mushrooms (Agaricus bisporus) which results in consumer demand loss at the marketplace. The main aim of this study was identification of bacteria causing blotches in some mushroom cultivation centers of Chaharmahal-o-Bakhtiari province. Mushrooms with cream to brown or black blotches on caps and stems were collected and bacterial isolation was done. The phenotypic characteristics of isolates were investigated. Pathogenicity tests were performed on excised tissue blocks, on intact caps and by injection to stipe of A. bisporus. Some of pathogenic isolates were identified as Pseudomonas tolaasii based on phenotypic characters and detection by Pt1A/1D primer sets in PCR. The others were identified as Ewingella americana based on phenotypic characters, pathogenicity on stipe and the partial sequence of 16S rDNA region. Based on pathogenicity tests, P. tolaasii isolates were divided in two distinct groups: high pathogenic and low/non-pathogenic. These two groups differed in some phenotypic characters such as type and color of colony, HR on geranium and potato rot test. To the authors'' knowledge, it is the first description of low/non- pathogenic isolate of P. tolaasii and the first report of E. americana from Chaharmahal-o-Bakhtiari province.

Species of the Botryosphaeriaceae have a worldwide distribution and some species of have been recognized as important pathogens on various trees worldwide. In order to identify the Botryosphaeriaceae species associated with olive trunk diseases, a survey was conducted on trees in Kerman and Mazandaran provinces. In 2016, wood samples were collected from trunk and branches of trees showing dieback and canker symptoms. Fungal isolations were performed from discolored wood tissues on potato dextrose agar (PDA). In this study 56 fungal isolates resembling Botryosphaeriaceae species in colony and culture were obtained from affected trees. All isolates were identified using morphological characteristics and partial sequences of the translation elongation factor 1-α gene (tef-1α) with the primer pairs EF1-728F and EF1-986R. Based on morphological and molecular analysis five species of Botryosphaeriaceae namely, Botryosphaeria dothidea (11 isolates), Diplodia seriata (8 isolates), Dothirella sarmentorum (8 isolates), Lasiodiplodia theobromae (7 isolates) and Neoscytalidium hyalinum (22 isolates) were identified. A pathogenicity trial was performed on detached shoots of olive under greenhouse conditions. Diplodia seriata isolates were the most virulent species based on the length of wood necrosis. This study is the first report of D. seriata and L. theobromae from olive trees in Iran. In addition, this study is the first report of Do. sarmentorum associated with yellowing, canker and dieback symptoms of olive trees.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is the most destructive rust of wheat. In this study, in addition to determining the effectiveness of rust resistance genes, the responses of 48 wheat genotypes from the cold agro-climate zone of Iran, including commercial cultivars, candidate lines, and the lines of ERWYT-C-94 were determined to the disease. Disease score of differential cultivars carrying resistance genes to stem rust under field conditions showed the presence of virulence on 31 resistance genes. In this regard, virulence on Sr31 was new for Kelardasht and on Sr1RSAmigo and SrSatu for the whole country. Seedling evaluations of wheat genotypes in the greenhouse showed that three commercial cultivars including MV-17, Pishgam, and Gascogne, four candidate lines including C-88-7, C-88-14, C-89-7, and CD-89-10, and the elite line C-94-6 displayed the lowest infection types to different isolates of P. graminis f.sp. tritici. Adult-plant evaluations under field conditions showed that the candidate line CD-89-10, showing the response of 20R, was the most resistant line among all genotypes tested. Two candidate lines CD-90-4 and CD-90-8, displaying low infection types to most of the isolates, were also among the genotypes with good level of resistance to the disease at seedling stage. These lines, with the responses of 20MR and 40MR, respectively, had also acceptable levels of resistance at adult-plant stage. Considering high frequency of susceptible genotypes to stem rust in cold zone, especially the promising lines, transferring effective stem rust resistance genes to wheat cultivars for this zone is necessary.

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.

Description of Pratylenchus elamini Zeidan & Geraert, 1991 from IranManouchehr Hosseinvand, Shahin Ganjkhanloo and Ali Eskandari Our population identified by Geraert key (2013) as Pratylenchus elamini and agree well for most of the morphometrics and morphological aspects with the original description. This species has been originally described from Sudan by Zeidan & Geraert (1991). Rashno Bone Abbasi et al., (2018) only mentioned to Pratylenchus elamini name in list of identified species associated with citrus orchards in Dezful and Andimesk. In present study this species identified in rhizosphere of grass in Ijroud, Zanjan province and described for the first time from Iran.