Vegetative compatibility, host range and pathogenicity of Verticillium dahliae isolates in Iran

Verticillium wilt is an economically important disease which inflicts serious losses in potato, cotton, alfalfa, some vegetable crops and fruit trees and occasionally ornamentals. V. dahliae, infected cultivated species and weeds were collected from several areas in Iran during twelve years from 1993-2005 and studied for their vegetative compatibility, host range and pathogenicity. The pathogen was isolated from 27 species belonging to 24 genera and 15 families of plants but was most frequently isolated from Solanaceae, Cucurbitaceae, Oleaceae and Rosaceae hosts. The morphology of V. dahliae isolates on Czapecks agar and water agar media were different especially for micosclerotial appearance time (4-19 days), pigmented zone of colony (37.8-48.33 mm) and microsclerotial morphology (abundant, irregular and elongated shaped or more spherical and scattered). The ratio index of length/width of conidia ranged between 2.32 and 2.70 micrometer with an average of 2.43 + 0.11. Temperature influenced the radial growth ratio of the isolates and the growth response of V. dahliae isolates to temperature in vitro was quadratic. All isolates were categorized in three groups based on pathogenicity tests on differential test plants (cotton cv. Sahel and aubergine cv. local). A total of 548 V. dahliae isolates from different locations and hosts were assigned to vegetative compatibility groups (VCGs) using nitrate-nonutilizing (nit) mutants. A higher frequency of nit1/nit3 mutants (93%) were obtained compared to nitM (7%). Approximately 51.1% of the isolates were assigned to VCG4B, 25.9% to VCG2A and 23% to VCG1. The results demonstrated that V. dahliae isolates assigned to VCGs were closely associated with specific pathogenicity within the group/diverse

Strain-specific SCAR markers for the detection of Trichoderma harzianum AS12-2, a biological control agent against Rhizocto nia solani, the causal agent of rice sheath blight

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

Population genetic evidence that basidiospores play an important role in the disease cycle of rice-infecting populations of Rhizoctonia solani AG-1 IA in Iran

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 126-263km. Each field was sampled twice during the season: at the early booting stage and 45days 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=0·002) 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. © 2012 BSPP

Innovative method for traceability of hides throughout the leather manufacturing process

In this work, a novel technological solution for the traceability of hides throughout the leather manufacturing process is addressed. The proposed solution relies on marking the raw hide with a permanent sub-surface tattoo, made with specific substances used as identification markers. In practical applications, the markers can be embedded so as to form a pre-established pattern, thus creating a unique identification code. To experimentally demonstrate the feasibility of the proposed solution, in this work, different types of markers were injected in a raw hide (i.e., prior to its tanning). After the tanning process, the persistence of the markers and of their pattern was verified by comparatively inspecting the hide with two different sensing technologies: microwave reflectometry and X-ray imaging. The obtained results demonstrated that the proposed traceability system is a promising solution to circumvent the age-old problem related to counterfeiting and fraudulent substitutions of raw materials in the leather manufacturing industry