Mycologia Iranica
Volume:7 Issue: 2, Summer and Autumn 2020

The review provides an overview of the biological and taxonomical findings of the blast disease causal agent, Pyricularia oryzae, in Iran. Comprehensive and comparative symptomology and geographical distribution of the P. oryzae strains are described. The taxonomic history of the P. oryzae compares to close species is illustrated and the host specificity and the population genetics of the strains obtained from weeds and crops are elucidated. Sexual status and mating type information of P. oryzae are also discussed.

The new corticioid species Waitea guianensis was described and illustrated from French Guiana, based on morphological and molecular phylogenetic evidence. It was characterized by thin, resupinate basidiomata on wood, isodiametric subhymenial hyphae, lack of clamps, tetrasporic clavate basidia with median constriction, and ellipsoid basidiospores. Ex-holotype DNA sequences from the nuclear ribosomal regions ITS, nLSU, and nSSU were obtained. Phylogenetic analyses confirmed a close relationship of the new species to Waitea circinata. In addition, the new combination Waitea arvalis is proposed, based on Laetisaria arvalis. The monotypic genus Disporotrichum is revealed to belong in the Corticiales, Corticiaceae. A key to the accepted species in Waitea is provided.

During the study on boxwood blight from 2016 to 2017, some isolates of Pseudonectria were isolated from boxwood leaves and branches. Fungi were isolated and purified using conventional methods. According to the morphological characteristics and ITS rDNA sequences, two species of Pseudonectria viz. P. buxi and P. foliicola were identified. Moreover, the pathogenicity of these two species under laboratory and greenhouse conditions was examined. None of the species were able to produce disease on the healthy plant leaves, and leaf wounds were necessary to establish the infection. According to our knowledge, this is the first report of Pseudonectria species on boxwood from Iran.

Cellulose is the most abundant component of lignocellulose with a vast range of applications in various fields such as nanotechnology, pharmacy, food industry. The cellulase enzyme complex consists of three major enzymes, including endoglucanases, exoglucanases, and beta-glucosidases, which are capable of decomposing cellulose. In this study, various fungal species were isolated from the degraded woods of Arasbaran forests. The activity zone technique was used to screen cellulolytic fungi. Based on the results, three fungal isolates had the highest cellulolytic activity. Phylogenetic analysis was performed based on the Internal Transcribed Spacer (ITS) region and the isolates were classified into two genera as follows: Trichoderma and Aspergillus. The cellulolytic activity of three fungal isolates was measured by the DNS method and indicated thatT. harzianum has the highest activity (22.3 U/mg) compared with other isolates. Afterward, the growth condition of T. harzianum was optimized by Response Surface Methodology (RSM) to obtain a high amount of cellulase activity. The results indicated that the maximum amount of cellulase production (38.3 U/mg) was observed at 1.5% CMC, 0.51% peptone, pH 5, temperature 26.4°C, and incubation for about 3 days. Therefore, T. harzianum could be considered as a potential candidate for genetic improvement and enzyme production.

Athelia rolfsii is a globally dispersed pathogenic fungus, causing white root rot disease in many crops and horticultural plants. In this study, 90 isolates were collected from three provinces of Guilan, Mazandaran and Golestan in northern Iran. Eighteen isolates were selected for sequence analyses based on their host, sampling sites and Mycelial Compatibility Groups (MCG). Translation elongation factor 1-α(tef1-α), β-tubulin (tub2) genes and rDNA large subunit (LSU) were partially amplified and sequenced in order to conduct phylogenetic analyses. Approximately, all Iranian isolates clustered together in both tef1-α and LSU phylogenetic trees. However, after deletion of ambiguous sites, no variations were observed in tub2 sequences. ISSR and SCoT were also used to investigate the genetic structure of the population. Results of the molecular variance analysis (AMOVA) showed that 70 and 30% of the observed variance corresponded to the difference between and within the populations, respectively. According to these findings, we suggest that mating between populations would be less likely and thus, gene flow is restricted.

In a recent survey on apple orchards showing stem canker, dieback and decline symptoms in West Azerbayjan province, Iran, several fungal isolates with typical characteristics of the genus Cytospora were obtained. Combination of morphological and cultural characteristics and phylogenetic analysis of internal transcribed spacer region of the nrDNA (ITS-rDNA) and parts of large subunit of ribosomal DNA (LSU), actin (ACT) and RNA polymerase II (RPB2) genes were used to accurate delimitation of fungal species. Four Cytospora species viz. C. chrysosperma, C. germanica, C. paratranslucens and C. salicina were identified. Pathogenicity tests were conducted on detached branches of ‘Golden delicious’ and ‘Red delicious’ apple cultivars. Isolates of C. salicina caused characteristic lesions on both ‘Golden delicious’ and ‘Red delicious’ apple cultivars, while isolates of C. chrysosperma, C. germanica and C. paratranslucens were only pathogenic on ‘Red delicious’ apple cultivar. Re-isolation and identification of the inoculated fungi confirmed Koch’s postulates. This study indicated the presence of different Cytospora species causing apple canker, dieback and decline disease in the studied area. Cytospora germanica and C. salicina are reported for the first time as causal agents of apple canker disease. Moreover, these species are reported as new records for the mycobiota of Iran.

In an investigation of the biodiversity of endophytic fungal species associated with saffron plant in Iran's main saffron cultivation regions, five isolates belong to Talaromyces genuswere obtained. The isolates identified as Talaromyces versatilis, T. aurantiacus, T. pinophilus, T. funiculosus, and T. purpureogenus by morphological and molecular criteria. To our knowledge, two species, including Talaromyces versatilis and T. aurantiacus are the first reports for the mycobiota of Iran.

In order to study of cabbage leaf spot disease in Damavand region, Tehran province, Iran, symptomatic cabbage leaves (Brassica oleracea var. capitata) were collected during the late summer and fall of 2017. Twenty-one isolates with the main characteristics of the genus Alternaria were isolated from lesions on the cabbage leaves. Based on morphological characteristics and phylogenetic analysis using multi-gene sequences, they were identified as Alternaria telliensis. Pathogenicity tests were conducted on cabbage leaves under greenhouse conditions and characteristic lesions were formed on inoculated leaves. Re-isolation of the inoculated fungus from the treated leaves confirmed Koch’s postulates. Based on the available information, this is the first occurrence of A. telliensis as a new species and pathogen to cabbage plants in Iran.

Strawberry is a major fruit cultivated in Kerman greenhouses. During visiting strawberry cultivation greenhouses, black root rot symptoms were detected on strawberry plants. In order to identify the causal agents of the disease, symptomatic tissues were collected and transferred to the laboratory. Cylindrocarpon-like isolates were consistently recovered from infected tissues.  Based on morphological characteristics as well as sequence data, the causal agent was identified as Dactylonectriamacrodidyma. Colonies of D. macrodidyma on PDA were brown with yellow (honey) pigmentation at the margins. Macroconidia on SNA medium were 1–3 (–4) septate, straight, cylindrical (sometimes widening toward the tip), apical cell slightly bent to one side, 40 (±11) × 6.3 (±1.8) µm with free-standing, slender, unbranched conidiophores. Microconidia with 0–1 septum, ellipsoid and ovoid 10.5 (±3.2) × 4.1 (±1.6) µm. The results of pathogenicity tests showed that the tested isolates were pathogenic to strawberry. According to the knowledge, this is the first report of D. macrodidyma on strawberry.

An extensive survey on phylogeny and pathology of fungi associated with the oak decline in Zagros forests located in Western Azarbaijan, Kurdistan, Kermanshah, Lorestan, and Ilam provinces, a large number of collected fungal isolates seventeen isolates morphologically resembled the members of Phaeoacremonium. Similar DNA fingerprinting patterns were generated for all isolates using M13 primer. Thus, one representative isolate (IRAN 4348C) was analyzed based on tub2 sequence data using maximum parsimony and neighbor-joining algorithms and identified as Phaeoacremonium tuscanicum. Pathogenicity was confirmed following Koch’s postulates on two-year-old Quercus brantii seedlings under greenhouse conditions. To our knowledge, it is the first time Ph. tuscanicum is reported from oak trees and confirmed as a pathogenic fungal species on Q. brantii in the world.

Linum usitatissimum, known as flax, is grown all around the world. Powdery mildew is a common disease on this crop so that this disease has been described from most flax-growing areas of the world. Clear symptoms of powdery mildew were observed on the field of different flax cultivars of Seed and Plant Improvement Institute of Iran in 2020 growing season. The causal pathogen of flax powdery mildew was identified as Podosphaera lini based on the morphological features and the nuclear ribosomal DNA internal transcribed spacer sequence. This is the first documented report of P. lini from flax in Iran.