Application of candidate endophytic fungi isolated from extreme desert adapted trees to mitigate the adverse effects of drought stress on maize (Zea mays L.).

The survival of plants under adverse conditions in desert habitats is related to microbial interactions, which can be an innovative strategy for reducing the effects of drought stress in colonized plants. In this study, two endophytic fungi, Trichoderma harzianum, and Fusarium solani, were recovered from the roots of trees in desert regions of Iran. A greenhouse experiment with two fungal agents (control, T. harzianum, F. solani, and T. harzianum + F. solani) and drought (100, 75, and 50% water-holding capacity) was performed on maize (Zea mays L.). Findings indicate that increasing drought levels negatively affect maize plant growth and physiological traits. However, the symbiotic relationship between fungal endophytes and maize roots increased fresh and dry biomass, root/shoot ratio, leaf area, relative water content, and membrane stability index compared with their control counterparts. Maize plants inoculated with endophytic fungi had 52.07, 40, 33.03, and 55.62% higher total phenolic, proline and soluble sugar concentrations, respectively than uninoculated controls. Photosynthetic parameters, including chlorophyll and carotenoid pigments, chlorophyll fluorescence, and gas exchange, were improved in the endophyte-treated plants. However, with increasing drought stress, maize plants colonized with endophytes, electrolyte leakage, and sub-stomatal CO2 concentrations decreased by 28.93% and 47.62%, respectively, compared to endophyte-free plants. When plants were exposed to higher levels of drought stress, endophytes were more effective in improving most parameters, and inoculation of maize seedlings with a combination of endophytes isolated from plants in harsh regions was more effective in increasing their tolerance to drought stress than individual inoculation of each fungus.

Molecular Variability of the Fusarium solani Species Complex Associated with Fusarium Wilt of Melon in Iran.

Species of the Fusarium solani species complex (FSSC) are responsible for the Fusarium wilt disease of melon (Cucumis melo), a major disease of this crop in Iran. According to a recent taxonomic revision of Fusarium based primarily on multilocus phylogenetic analysis, Neocosmospora, a genus distinct from Fusarium sensu stricto, has been proposed to accommodate the FSSC. This study characterized 25 representative FSSC isolates from melon collected in 2009-2011 during a field survey carried out in five provinces of Iran. Pathogenicity assays showed the isolates were pathogenic on different varieties of melon and other cucurbits, including cucumber, watermelon, zucchini, pumpkin, and bottle gourd. Based on morphological characteristics and phylogenetic analysis of three genetic regions, including nrDNA internal transcribed spacer (ITS), 28S nrDNA large subunit (LSU) and translation elongation factor 1-alpha (tef1), Neocosmospora falciformis (syn. F. falciforme), N. keratoplastica (syn. F. keratoplasticum), N. pisi (syn. F. vanettenii), and Neocosmospora sp. were identified among the Iranian FSSC isolates. The N. falciformis isolates were the most numerous. This is the first report of N. pisi causing wilt and root rot disease in melon. Iranian FSSC isolates from different regions in the country shared the same multilocus haplotypes suggesting a long-distance dispersal of FSSC, probably through seeds.

Genome sequences of 38 Fusarium oxysporum strains.

OBJECTIVE: Wilt caused by Fusarium oxysporum f. sp. melonis (Fom) is one of the most widespread and destructive melon diseases worldwide. Whole-genome sequencing data of a diverse set of Fom strains, as well as several non-pathogenic strains isolated from melon from different parts of the world are described here. These data shed light on the genetic diversity, population structure and the potential evolutionary trajectories which have led to the emergence of different Fom races, and will facilitate identification of avirulence genes which will be helpful to develop resistant melon cultivars. DATA DESCRIPTION: Genomic DNA was extracted from mycelium of 38 Fusarium oxysporum (Fo) strains collected from different parts of the world including Belgium, China, France, Iran, Israel, Japan, Mexico, New Zealand, Spain, the Netherlands, and the United States. The genomes were sequenced to ≈ 20 × coverage using the Illumina Hiseq Xten system, resulting in paired-end reads of 151 bp and assemblies of 1675 (Fom-18L) to 4472 (Fom-R12-13) scaffolds. The genome sequences are available in the National Center for Biotechnology Information (NCBI) and the Sequence Read Archive (SRA) under Project number PRJNA596396 and PRJNA596396, respectively. The presented data set can be useful to identify the genes associated with pathogenic strategies.

Comparative genomics of Fusarium oxysporum f. sp. melonis strains reveals nine lineages and a new sequence type of AvrFom2.

Fusarium oxysporum f. sp. melonis (Fom) is one of the most important pathogens of melon worldwide. In this study, we investigated the genomic diversity of Fom. One of the aims was to find clues for the origin(s) and dispersal of clonal lineages and races of Fom. We therefore included a large number of Fom strains from Iran, where melon has been cultivated for at least 5000 years. In 33 new genome sequences of Fom strains from different geographical regions of Iran and across the world, 40 new candidate effector genes were identified. Presence/absence of candidate effector genes and phylogenetic analyses resolved nine Fom lineages. The presence of a highly similar set of effector genes in some distant lineages is suggestive of horizontal chromosome transfer, a process known to occur in the Fusarium oxysporum species complex. Race 1.2, which breaks both Fom1 and Fom2 resistance genes, occurs in three of the nine lineages, two of which are predominant in Iran. We also identified a new sequence type of the AVRFom2 avirulence gene in one lineage. Expression of this sequence type during melon infection and genetic complementation suggest that this sequence type is not recognized by the Fom2 resistance protein.

Species-specific ITS primers for the identification of Picoa juniperi and Picoa lefebvrei and using nested-PCR for detection of P. juniperi in planta.

Desert truffles, hypogeous Pezizales (Ascomycota), are difficult to identify due to evolutionary convergence of morphological characters among taxa that share a similar habitat and mode of spore dispersal. Also, during their symbiotic phase, these are barely distinguishable morphologically, and molecular probes are needed for their identification. We have developed a PCR-based method for the identification of Picoa juniperi and Picoa lefebvrei based on internal transcribed spacers of rDNA. Two PCR primers specific for P. lefebvrei (FLE/RLE) and two specific for P. juniperi (FJU/RJU) were designed. A collection of samples from different geographical areas representing diversity of these species were examined for unique regions of internal transcribed spacers 1, 2 and 5.8S gene of rDNA (ITS) compared to other closely related species. Annealing temperatures and extension times were optimized for each set of primers for maximum specificity and efficiency. They proved to be efficient to specifically detect the presence of P. juniperi and P. lefebvrei by PCR and neither set amplified purified DNA from other truffle species as well as some ascomycetous fungi. The partial small subunit of ribosomal DNA genes of P. juniperi were amplified with the genomic DNA extracted from Helianthemum ledifolium var. ledifolium roots by nested polymerase chain reaction (PCR) using the universal fungal primer pair ITS1/ITS4 and specific primer pair FTC/RTC, which was designed based on internal transcribed spacer 1, 2 and 5.8S gene of rDNA sequences of P juniperi. The nested-PCR was sensitive enough to re-amplify the direct-PCR product, resulting in a DNA fragment of 426 bp. The efficacy of nested-PCR showed that it could re-amplify the direct-PCR product and detect 200 fg genomic DNA.

Novel Phaeoacremonium species associated with Petri disease and esca of grapevine in Iran and Spain.

Eight Phaeoacremonium (Pm.) isolates from grapevines in Iran and Spain were studied with morphological and cultural characteristics as well as phylogenetic analyses of combined DNA sequences of the actin and beta-tubulin genes. Two new species are described. Pm. cinereum was isolated from a young vine in Spain and from older vines in Iran and can be identified by its distinct gray colonies on malt extract agar, an optimum growth temperature of 25 C and subulate type III phialides. Pm. hispanicum was isolated only once from a young vine in Spain and can be identified by the common occurrence of percurrently rejuvenating phialides, an optimum growth temperature of 20 C and predominant type II phialides.