Stem canker and black scurf of potato (Solanum tuberosum L.) caused by Rhizoctonia solani Kühn are important and epidemic diseases in potato-growing regions worldwide, including Iran. In this study, 120 isolates were retrieved from infected stem canker from six potato- growing regions in Iran (Isfahan, Ardebil, Fars, Hamedan, Kurdestan and Kerman). Out of these, 30 isolates were selected as representatives for genetic and virulence analysis. The isolates were analyzed by one sequence analyzes of the ITS-rDNA region, random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), as well as virulence studies. Based on sequence analysis of the ITS-rDNA region, all 30 isolates were assigned to the anastomosis group (AG) and all were assigned to AG-3 PT. Cluster analysis using the unweighted pair group method with the arithmetic averages (UPGMA) method for both RAPD and ISSR markers revealed that they were divided into three main groups, with no correlation to geographical regions of the isolates. Pathogenicity tests showed that all isolates were pathogenic on potato cv. Agria; however, virulence variability was observed among the isolates. The grouping based on RAPD analysis and virulence variability was not correlated.

Habitat fragmentation is one of serious threats to biodiversity of nature in today's world. The present study of a typical steppe species Iris pumila L. (Iridaceae) has analyzed the impacts of geographical isolation and population size on genetic diversity and population structure in conditions of habitat fragmentation. The key indices of population genetic variability calculated from the ISSR markers data were on average as follows: Shannon diversity index (S) – 0.188; unbiased Nei’s gene diversity (He) – 0.123; and the average measure of Jaccard’s genetic distances between individuals within populations – 58.4%. Although the largest population had significantly higher values of S and He, the small and marginal populations also showed a comparable level of variation. Most of the genetic variation of I. pumila was distributed within the populations. A strong correlation was found between Nei’s genetic distances and geographic distances between the populations. According to the Bayesian analysis, genetic structure of the populations was highly homogeneous; however, the presence of admixed genotypes indicated the possibility of gene flow between the populations at present.

Potato leaf blight disease caused by Ulocladium atrum (Syn. Stemphylium atrum) is an important and epidemic disease in potato-growing regions of Iran. In this study, 30 isolates of the disease were collected from the main potato-growing regions of Iran and were analyzed on the basis of morphological characterization and pathogenicity. Based on morphological characteristics, all isolates were identified as U. atrum. Pathogenicity studies indicated that all 30 isolates were pathogenic on potato “Agria” to varying degrees. Five U. atrum isolates causing potato leaf blight disease, obtained from the Plant Pathology Laboratory, Isfahan Research Center for Agriculture and Natural Resources, Isfahan, Iran, were also examined in this study. A total of 35 isolates were genetically analyzed using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers. Cluster analysis using the un-weighted pair group method with the arithmetic average (UPGMA) method for RAPD marker revealed no clear grouping of the isolates obtained from different geographical regions. The groupings, based on morphological characteristics, virulence variability and RAPD analysis, were not correlated. Cluster analysis using Jaccard’s coefficient for ISSR divided the U. atrum isolates into four main groups, in which there was no significant correlation between the isolate groupings regarding their geographic location and pathogenicity. Using molecular techniques genetic variability was detected among the accessions, with cophenetic correlation coefficients (CCC) of 0.80 for RAPDs and 0.89 for ISSRs. The RAPD and ISSR marker results corresponded well, with a correlation of 0.55.

This study used ISSR markers to assess the genetic diversity of a collection of 15 genotypes of Salix purpurea and 6 interspecific hybrids, employing 40 of 60 tested ISSR primers generating polymorphic amplification products. The PCR-ISSR method was adapted for S. purpurea by optimizing the annealing temperature for each primer. The polymorphism index of ISSR amplification products was 91.8% for all studied genotypes and 70.4% for S. purpurea genotypes. Nei's genetic identity statistics ranged from 0.538 to 0.958. Nei's genetic distance values were used to build a dendrogram (UPGMA) for the investigated genotypes. The dendrogram shows five clusters, and principal coordinate analysis yielded nearly the same genetic relationships among the studied genotypes. The results confirm the usefulness of ISSR markers for determining genetic diversity in S. purpurea.

This communication reports detection of somaclonal variation among tissue culture-raised plants of Amorphophallus rivieri Durieu, an economically important crop in China, with high content of glucomannan in its corms. A population of regenerated plants was obtained from a single donor plant of A. rivieri via corm organogenesis, and 28 plants were randomly selected as a representative sample and subjected to analysis of somaclonal variation using inter-simple sequence repeat (ISSR) markers. Of the 26 ISSR primers screened, 13 gave distinct and reproducible band patterns, yielding 131 bands with an average of 10.1 bands per primer. Ten primers were polymorphic and generated 16 polymorphic bands with 12.2% mean polymorphism. Based on the ISSR data from the regenerated plants and the donor plant, Jaccard's similarity coefficients were calculated; they ranged from 0.961 to 1.000 with a mean of 0.982. A dendrogram was constructed using the unweighted pair group method with arithmetic mean (Upgma); it showed that a majority of regenerated plants (including the donor plant) clustered closely, with a mean similarity coefficient of 0.987. Low somaclonal variation observed in the regenerated plants indicates that rapid propagation of A. rivieri via corm organogenesis is a practicable method with a low risk of genetic instability.

Genotypic differentiation among 10 isolates of Phytophthora cinnamomi Rands and 24 isolates of Phytophthora citricola Sawada from 12 different plant species grown in Polish ornamental nurseries was determined. DNA was extracted from pure pathogen cultures and amplified by the PCR technique using ISSR and RAPD primers. 9 primers were used to amplify P. cinnamomi and 8 to amplify P. citricola DNA. The analyzed amplification products were between 300 and 2300 bp. The genotypical differentiation was from 17 to 35% in P. cinnamomi and from 10 to 60% in P. citricola. Isolates from host plants of the same family showed, with some exceptions, similar levels of differentiation.