IRANIAN JOURNAL OF PLANT PATHOLOGY
Year:2018 | Volume:54 | Issue:1|Papers Count:7

Pink rot, caused by Phytophthora erythroseptica, is an important soil-borne disease of potato causes significant losses in the field and storage. A selection of P. erythroseptica isolates from potato-growing regions in four continents including America, Asia, Europe and Australia was assessed using phylogenetic, morphological and physiological analyses. In all nuclear (internal transcribed spacers, ß-tubulin and heat shock protein 90) and mitochondrial (cytochrome c oxidase subunit I) trees as well as combined nuclear and mitochondrial tree, P. erythroseptica isolates formed a separate phylogenetic lineage containing the type isolate. Additionally, no morphological and physiological diversities were observed among the isolates. All isolates were homothallic and produced amphigynous terminal antheridia and globose aplerotic oogonia as well as non-papillate and ellipsoid to ovoid sporangia. The results showed that P. erythroseptica isolates belonged to different geographic regions are phylogenetically and morphologically similar. This uniformity could be due to the homothallic nature of P. erythroseptica or distribution of a single clone of pathogen by infected potato.

The aim of this research was to compare the pathogenicity and some biological and morphological characters of four populations of the sugar beet cyst nematode Heterodera schachtii, collected from infested farms of Isfahan, Shiraz, West Azerbaijan and Khorasan provinces. The responses of 12 sugar beet genotypes were evaluated in greenhouse based on the female number on the roots. Moreover, the sizes of females of the nematode populations on each genotype were determined, and egg hatching and emergence of the second stage juveniles (J2s) from the cysts were compared. The cluster analysis of genotypes based on the number and size of the females on the plants showed that the genotypes Toucan, Cactus, Fernando, Sanetta cultivars were clustered with the resistant cultivar Pauletta in one group, and the genotypes 035, 7112*SB36*SB30, 031, 034 and 7112*SB36*SB28 were clustered with the susceptible control (7112*SB36*SB29) in another group. Fewer and smaller females were produced on the resistant genotypes. Nematode population of West Azerbaijan showed a noticeable difference in pathogenicity with Isfahan population and produced fewer and smaller females. Mashhad population had the highest rate of egg hatching and juvenile emergence from cysts compared to the other populations.

Legume diseases characterized by yellowing, stunting and leaf rolling cause heavy losses to legume crops. One of the causal agents of these diseases is Bean leaf roll virus (BLRV) which is widespread in legume species throughout Iran. In the present research, genetic variation of BLRV isolates from different plants and different geographical regions is investigated. Samples of Vicia faba, Pisum sativum, Cicer arietinum, Medicago sativa, Lens culinaris, Trifolium spp., Trigonella foenum-graecum and Phaseolus vulgaris showing symptoms of yellowing, dwarfing and leaf rolling were collected from the fields of Markazi, Fars, Khuzestan, Kohgiluye-va-Boyerahmad, Golestan, Zanjan and Qazvin provinces in 2016-2017. Total RNA was extracted from symptomatic samples and subjected to RT-PCR using specific primers amplifying a fragment of 389 bp in size from the CP region of the virus which was cloned and sequenced. BLRV was detected in faba bean, alfalfa, lentil, chickpea, bean and clover. Comparison of obtained nucleotide (nt) and amino acid (aa) sequences of Iranian isolates of BLRV with corresponding nt and aa sequences of other BLRV isolates available in GenBank showed a 94-98% and a 96-100% nt and aa similarity, respectively. Phylogenetic analyses indicated that all Iranian BLRV isolates constituted a group district from the group formed by non-Iranian BLRV isolates. These data indicated that the CP region of this virus is relatively conserved among different isolates of BLRV.

Maize Iranian mosaic virus (MIMV) is a distinct member of the genus Nucleorhabdovirus. The genetic diversity of maize Iranian mosaic virus (MIMV) isolates collected from different geographical regions of Iran, different hosts and different symptoms was determined during 2015-2016. Selection pressure analyses were also performed. Sequences of the nucleocapsid protein, glycoprotein, and a 500 bp fragment of polymerase genes and non-coding regions were determined. Genetic diversity in coding regions was less than 1. 3 % in nucleocapsid protein and glycoprotein genes and 1 % in polymerase gene. The diversity in non-coding sequences was higher compared to ORFs especially between P and ORF 3 (up to 14. 7 %). In phylogenetic analysis no correlation was found between MIMV isolates and geographical regions, type of symptoms and host differences. The ratio of non-synonymous to synonymous polymorphic sites indicated purifying selection has acted upon the analyzed genes. Likely, the dependence of MIMV on planthoppers for spreading can explain its low diversity. The information on the low genetic diversity of MIMV will be helpful in selection of maize cultivars with durable resistance.

The high temperature-tolerant oomycete Phytophthora parsiana was considered to be limited to woody plants. In the preliminary study, the host range of the pathogen on annual herbaceous plant species using six isolates of P. parsiana including type strains from different sources was examined under greenhouse conditions. Among herbaceous species including cucurbits, pepper, pulse and oil crops, two isolates were pathogenic to pepper. Then three cultivars of pepper were used to discriminate pepper cultivars to sixteen isolates of P. parsiana. Results showed P. parsiana were pathogenic to red pepper (‘ Anheim’ and ‘ Casabel’ cultivars) but not bell pepper. This is the first report of an herbaceous host of P. parsiana (sensu lato). Phylogenetic relationships of the pathogenic isolates of P. parsiana from pistachio to pepper and two isolates of the species from pistachio from Rafsanjan and Yazd were not pathogenic to pepper were examined. Based on sequences of the internal transcribed spacer (ITS) region of the ribosomal RNA, isolates pathogenic to pepper and one from Rafsanjan were in a group of P. parsiana belonging to clade 10 but the Yazd isolate had no genetic similarity to P. parsiana, being placed in clade 6 of the ITS tree, closely matching that of Phytophthora taxon Walnut (99-100 nucleotide identity). This is the first report of Phytophthora taxon Walnut from pistachio in Iran.

Eldar pine (Pinus eldarica Medw., Pinaceae) is among the most popular and commonly planted ornamental trees in Northern and Central Iran. Rust infected specimens of Eldar pine were collected from pine cultivated forest at Hezaar-Pich, Gorgan, Golestan province, in April 2012 and submitted to the Botany Department of Iranian Research Institute of Plant Protection, Tehran for diagnosis. The specimens showed heavy rust diseases symptoms including aecia on needles of Eldar pine. A description of the causal agent follows: Spermogonia subepidermal, on both sides of infected leaves. Aecia mostly hypophyllous, develop as conspicuous white columnar pustules on pine needles, peridermioid, with strongly developed bullate or tongue-shaped peridium, 1. 5-3 x 0. 5 mm and up to 1. 2 mm high. Aeciospores catenulate, 25-40 x 17. 5-26. 5 μ m, ellipsoid, oblong ellipsoid or more or less globoid, spore wall covered by rod-like verrucae (verrucose), wall including verrucae 2. 5-4 μ m thick, discrete rods up to 2. 5 μ m high, occasionally reduced on one side of spores or united in irregular or pseudoreticulate patterns (Fig. 1). Based on infection pattern and above mentioned morphological features of aecia and aeciospores, the rust fungus was identified as Coleosporium tussilaginis (Pers. ) Lev. (Majewski 1977). The voucher specimen, 17001F, was deposited in IRAN, Iranian Research Institute of Plant Protection, Tehran. This is the first report of C. tussilaginis on a member of Pinaceae in Iran. Moreover, Pinus eldarica, is reported as a new host for the rust. Coleosporium tussilaginis is a heteromacrocyclic rust with telial stage on members of Asteraceae family including species of the genera Tussilago, Senecio, Petasites and Sonchus (Braun 1981).

The genus Campydora Cobb, 1920, has a unique status among the phylum Nematoda based on head shape and the structure of esophagus. The genus has shown a common ancestor with the genera Alaimus, Tripyla, and Ironus under the order Enoplida as inferred from 18S ribosomal DNA sequence studies (Mullin et al., 2003). The family Campydoridae Thorne, 1935 contains only one genus and a single species without any additional species or genus. Sturhan (2010), found and reported Campydora demonstrans from Qazvin, Mashhad and Khorramabad regions in Iran from rhizosphere soils of herbaceous, tomatoes, alfalfa and wheat fields. He did not provide information on the morphological and morphometrical characteristics of the populations, so far. A population of this species was collected from the soil around Miyaneh city, East Azarbaijan province and the nematodes extracted using Jenkins (1964) and transferred to anhydrous glycerin by De Grisse (1969) methods. They were mounted on microscopic slides and the morphological and morphometrical characters studied using an Olympus BX 41 optical microscope and digital images prepared by a DP50 camera.