First report of leaf spot caused by <Emphasis Type="Italic">Alternaria alternata</Emphasis> on <Emphasis Type="Italic">Drimia maritima</Emphasis>

Drimia maritima (squill) is a historically important medicinal plant. During the spring of 2016, small, yellow leaf spots, which became brown and finally necrotic, were observed on squill plants in Kohgiluyeh and Boyer-Ahmad Provinces in Iran. A fungus was consistently isolated from infected leaves and identified as Alternaria alternata based on morphological and phylogenetic analyses. Pathogenicity tests confirmed A. alternata to be the causal agent of the newly observed leaf spot disease. This is the first report of leaf spot on D. maritima caused by A. alternata in the world.     

Trichoderma species collected from Iran

In order to identify Trichoderma species isolated from Iran, Trichoderma selective media and malt extract agar (MEA) were used to isolate Trichoderma species from the soil samples. All the cultures were purified on 2% water agar by hyphal tip method prior to morphological examination.Morphological observations were carried out on the cultures grown on 2 % MEA and oat meal agar at 20℃ under ambient laboratory conditions.     

Occurrence,genetic diversity and pathogenicity characteristics of Pseudomonas viridiflava inducing alfalfa bacterial wilt and crown root rot disease in Iran

Alfalfa (Medicago sativa), the world’s most influential forage crop, is infected by many diseases such as alfalfa bacterial wilt disease. The causal agent of bacterial crown and root rot and wilt disease is Pseudomonas viridiflava, which is a substantial pathogen of alfalfa worldwide. This pathogen spreads through the xylem and under field conditions, plants show growth stunting, chlorosis and wilting symptoms not previously reported. In this study- the first on Pseudomonas viridiflava on alfalfa from Iran, we have investigated the pathogenicity and genetic diversity of Pseudomonas viridiflava in some parts of Iran. To survey the causal agent of the disease, symptomatic plants were collected from the main alfalfa growing area. Pathogenicity of the collected strains was confirmed on alfalfa plants under green-house conditions using a completely randomized design. Determination of bacterial strains was done based on standard bacteriological methods and PCR assay using specific primers. Effects of bacterial strains on wet weight, dry weight, stem length and root length of infected plants were measured and the data were analyzed by SAS software and Duncan’s assessment. The diversity of liquid cellular proteins of bacterial strains was examined on Polyacrylamide gel. To delineate of genetic diversity the total DNA was drawn out. Fourteen random primers were used in a RAPD test. To sketch the dendrogram, RAPD fragments were used to calculate genetic diversity with NTSYS software. This data showed pathogenicity and genetic diversity of Pseudomonas viridiflava in Iran.     

Trichothecene production by Trichoderma brevicompactum

Trichoderma brevicompactum, T. viride, T. harzianum, T. atroviride, T. longibrachiatum, T. erinaceum, T. citrinoviride, and Hypocrea lutea were screened for production of trichothecenes after growth on one or several solid and liquid media. Trichothecenes were detected by liquid chromatography combined with online UV/vis spectroscopy and electrospray high-resolution mass spectrometry. T. brevicompactum produced trichodermin and/or harzianum A on all media investigated, with liquid media yielding the largest amounts. Detection of octa-2Z,4E,6E-trienedioic acid in the harzianum-A-producing strains indicated that harzianum A was synthesized directly by esterification of trichodermol with octa-2Z,4E,6E-trienedioic acid. Both the T. viride strain from which trichodermin was originally isolated and the T. harzianum strain from which harzianum A was originally isolated were shown to belong to T. brevicompactum based on four independent criteria: metabolite profiles, micromorphology, macromorphology on yeast extract sucrose agar and potato dextrose agar, and DNA sequences of the ITS1/ITS2 regions of the nuclear ribosomal DNA.     

BAFF-R, a newly identified TNF receptor that specifically interacts with BAFF

B cell homeostasis has been shown to critically depend on BAFF, the B cell activation factor from the tumor necrosis factor (TNF) family. Although BAFF is already known to bind two receptors, BCMA and TACI, we have identified a third receptor for BAFF that we have termed BAFF-R. BAFF-R binding appears to be highly specific for BAFF, suggesting a unique role for this ligand-receptor interaction. Consistent with this, the BAFF-R locus is disrupted in A/WySnJ mice, which display a B cell phenotype qualitatively similar to that of the BAFF-deficient mice. Thus, BAFF-R appears to be the principal receptor for BAFF-mediated mature B cell survival.     

Discula quercina as a possible causal agent of dieback on oak trees in Iran

During spring and summer of 2016, dieback symptoms including blights of leaves, twigs, and acorns were observed on current year shoots of Quercus infectoria in the Zagros oak forests of Iran. The fungus isolated from damaged tissues was identified as Discula quercina based on both morphological characteristics and ITS sequencing. To fulfil the Koch's postulates, a representative isolate was inoculated onto shoots of Q. infectoria and Quercus libani in both laboratory and forest conditions. Responses of the two oak species to inoculation with D. quercina were examined under laboratory and forest conditions in a completely randomized experiment. Discula quercina was clearly involved in oak dieback, and Q. infectoria was more susceptible than Q. libani to damage by the pathogen. This is the first record of the occurrence and pathogenicity of the fungus Discula quercina on Quercus infectoria. The fungus is considered as an emerging pathogen on oak trees in Zagros forests in Iran. Furthermore, the pathogenicity of the Discula quercina on Q. libani under laboratory and forest conditions increases the potential importance of this pathogen in Zagros forests.     

Overexpression of phytoglobin in barley alters both compatible and incompatible interactions with the mildew pathogen Blumeria graminis

This study showed how barley plants can be shifted in their response to isolates of the mildew pathogen Blumeria graminis with different host adaptation by overexpression of the barley phytoglobin gene HvHb1. At early infection stages, plants overexpressing phytoglobin (GPHb1) showed less papilla formation and more hypersensitive response against both virulent and avirulent pathogen isolates compared to the wildtype (WT) plants. The shift was most pronounced in a wheat-adapted isolate (B. graminis f. sp. tritici). At later infection stages, GPHb1 plants infected with a virulent pathogen isolate (A6) showed less leaf chlorosis compared to the WT plants, indicating delayed senescence. The chlorophyll level was significantly higher in A6-infected GPHb1 plants 9 days after inoculation (dai) and the senescence indicators sphingosine-1-phosphate:ceramide ratio and phytol content confirmed delayed senescence. At 14 dai the percentage of fungal DNA was significantly higher on the GPHb1 plants than on WT plants, probably as a result of the delayed senescence. The results show that overexpression of phytoglobin (previously known as plant haemoglobin) can be an important tool to understand disease-related stress effects in plants of agronomic importance and for understanding basic resistance mechanisms. Studying this process in more detail may provide insights into how to alleviate stress-related senescence in plants.