Filenchus annulatus is redescribed and males are characterised for the first time based on a population found in Northem Khorasan province, Iran. New morphological characterisation is based on light and scanning electron microscopy. In addition, molecular analyses based on 18S and 28S genes are included to test monophyly of the genus. Females from the Iranian population have a spermatheca typically filled with sperm. Generally males are similar to females, ranging from 306 to 426 ßm long. Spicules are arcuate, cephalated and 11.5-14.0 ßm long, the gubernaculum is minute and trough-shaped and the caudal alae are adanal. Phylogenetic analyses differed in results depending on the gene used: 28S gene strongly supports Filenchus as monophyletic whereas 18S shows Filenchus as polyphyletic. In both gene phytogenies, F annulatus is placed as a sister taxon of F quartus from Wyoming, USA. Although sequence divergence between these two species is only 3 base pairs and 1 base pair for 28S and 18S genes, respectively, strong morphological differences support their species status. Relationships between Filenchus and other Tylenchidae genera are also gene dependent. Such differences in tree topologies and branch support are related to the number of Filenchus species used in the analyses (greater for 18S gene) and gene resolution (greater for 28S gene). Molecular phytogenies also suggest that other Tylenchidae genera {i.e., Fsilenchus, Cephalenchus and Futylenchus) belong to separate clades, as is also suggested by some morphology-based classifications. The inclusion of more taxa and perhaps additional genes is needed further to clarify Filenchus relationships and further to test its monophyly.
The most frequently soil-borne fungal pathogens on plants are Fusarium species that make high economical damages in various agricultural locations in Iran. Our studies show that Fusarium species cause significant yield losses in main crops especially potato, pea, bean, wheat, corn and rice in several parts of the country. The diseases resulted in yield losses to the extent of 30 to 70% in the fields and made economical problems for growers. Infected plants were collected and cultured on common medium; potato dextrose agar (PDA) and selective media [peptone pentachloronitrobenzene (PCNB) agar (PPA), and carnation leaf agar (CLA)] for Fusarium species, and then isolated species were identified. The dominant species were F. solani, F. oxysporum, F. pseudograminearum, F. moniliforme and F. sambucinum in the area studied. Soil solarization method was carried at the summer season in three soil infested locations to assess the control management of the pathogens. Application of this method reduced population density of the pathogen from 1833 to 500, 266, and 100 CFU g-1 /soil after 2, 4, and 6 weeks. The method was simple, effective, non negative side and applicable in diverse farming areas at warm season.
In order to identify a specific marker for T. harzianum AS12-2, a strain capable of controlling rice sheath blight caused by Rhizoctonia solani, UP-PCR was performed using five universal primers (UP) both separately and in pairwise combinations. The application of two UP primers resulted in the amplification of unique fragments from the genomic DNA of T. harzianum AS12-2, clearly distinguishing it from other Trichoderma strains. The unique fragments had no significant sequence homology with any other known sequence available in databases. Based on the sequences of the unique fragments, 14 oligonucleotide primers were designed. Two primer sets amplified a fragment of expected size from the DNA of strain T. harzianum AS12-2 but not from any other examined strains belonging to T. harzianum, to other Trichoderma species assayed, or to other common fungi present in paddy fields of Mazandaran province, Iran. In conclusion, SCAR (sequence characterized amplified regions) markers were successfully identified and rapid, reliable tools were provided for the detection of an effective biocontrol Trichoderma strain, which can facilitate studies of its population dynamics and establishment after release into the natural environment.
The fungus Rhizoctonia solani AG-1 IA causes sheath blight, one of the most important rice diseases worldwide. The first objective of this study was to analyse the genetic structure of R. solani AG-1 IA populations from three locations in the Iranian Caspian Sea rice agroecosystem. Three population samples of R. solani AG-1 IA isolates were obtained in 2006 from infected rice fields separated by 126-263 km. Each field was sampled twice during the season: at the early booting stage and 45 days later at the early mature grain stage. The genetic structure of these three populations was analysed using nine microsatellite loci. While the population genetic structure from Tonekabon and Amol indicated high gene flow, they were both differentiated from Rasht. The high gene flow between Tonekabon and Amol was probably due mainly to human-mediated movement of infested seeds. The second objective was to determine the importance of recombination. All three populations exhibited a mixed reproductive mode, including both sexual and asexual reproduction. No inbreeding was detected, suggesting that the pathogen is random mating. The third objective was to determine if genetic structure within a field changes over the course of a growing season. A decrease in the proportion of admixed genotypes from the early to the late season was detected. There was also a significant (P = 0AE002) increase in the proportion of loci under Hardy-Weinberg equilibrium. These two lines of evidence support the hypothesis that basidiospores can be a source of secondary inoculum.
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