The accompanying text provides a comprehensive overview of fish DNA barcoding, a powerful molecular technique used for species identification and biodiversity assessment in ichthyology. DNA barcoding uses a standardized genetic marker, typically a segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene, to accurately identify fish species. This method has revolutionized biodiversity assessment, environmental monitoring, and detection of mislabeling in commercial seafood products. The text discusses the methodology of DNA barcoding, including the use of the COI gene as a standard barcode and the development of mini-barcoding techniques for degraded DNA samples. It also highlights the importance of DNA barcode databases such as the Barcode of Life Data System (BOLD) and GenBank in facilitating species identification and research. Major applications of fish DNA barcoding include species identification and discovery, assessing mislabeling in commercial seafood products, monitoring biodiversity in marine environments, and assessing anthropogenic pressures on aquatic ecosystems. Despite its many advantages, the text also acknowledges challenges and limitations, such as taxonomic resolution beyond the species level and dealing with cryptic species. Overall, barcoding fish DNA represents a significant advance in ichthyological research and closes the gap between traditional taxonomy and modern molecular biology.

DNA barcoding is a simple way to identify species using a very short genetic sequence from a standard part of the genome. This technique used to identify eight medicinal plants collected from the Ardabil province. DNA extraction was performed by modified CTAB method and PCR was performed with primers designed based on rbcL, trnH-psbA, matKChloroplast barcodes and ITS nuclear barcode. Then, PCR products purified and sequenced. The percentage of amplification and sequencing success were assumed in samples respectively, 87 and 62, 75 and 37, 62 and 12, 75 and 37. The sequences were blasted with samples existed in NCBI database and Bioinformatics analyses were performed. In phylogenetic tree, the species belonging to the same genus were separated from other genus based on rbcL and trnH-psbA barcode sequences. Also, in ITS barcode only G. glabra organized with plants from same genus. In this study, barcoding of L. ledebourii with rbcL was done for the first time. SNPs were counted for barcodes of rbcL (less than 30), trnH-psbA(less than100), ITS (more than 200) and matK (less than 20). Thus, rbcL barcode due to high separation ability, low number of SNPs and universality in most species, was introduced as the best barcode. However, trnH-psbA and ITS barcodes due to related problem with direct sequencing of PCR products and lack of access to high quality sequences were identified as complementary barcodes. MatK barcode is not recommended for these samples because of the low ability of amplification and sequencing.

Bark beetles as one of the most important pest group attacked to weak trees in forests and urban trees. Ulmus minor considers as an important host plant for bark beetles. This group of beetles feed on Phloem and transmit the pathogen of Dutch elm disease that cause high damage in Ulmus trees. The first and the most important step in preventing damage and bark beetles management is accurate identification of bark beetles. Because of small size and similarity in morphological characters of bark beetles, identification of this group is difficult and time consuming. In this study a DNA-based method barcoding was used to identify six bark beetles species that collected on Ulmus minor through sequencing 580bp of cytochrome oxidase one genome by using A2411 and C-N-J1718 universal primers. Obtained sequences were analyzed by MEGA ver.0 software. The results showed that the mean of interspecies nucleotide variation is 1.9% more than intraspecific variation 0.03% which confirmed DNA barcoding rule. The result showed that specimen identified in species level which proved DNA barcoding as a reliable tool to identify Ulmus bark beetles species.

DNA barcoding technique is a useful tool for the identification of plant and animal species using a short and standard sequence of the genome. In the present study, this method was used to identify four plant species including Calendula persica C. A. Mey., Silybum marianum (L. ) Gaertn., Satureja mutica Fisch. & C. A. Mey., and Malva neglecta Wallr. from the eastern Golestan province. The DNA was extracted by CTAB method and the PCR was performed with the primers designed based on the rbcL and trnH-psbA chloroplast barcodes and ITS nuclear barcode. The results of sequences were matched with the information in the NCBI database. The results showed that the all three barcodes were suitable for the samples studied due to their high resolution, low SNP number, and comprehensiveness in most species. Also, the barcodes comparison of the species collected from the rangelands and perfumeries showd that some plant species that are offered in the perfumeries are different from the plants that the natives use as medicine. It could be mentioned that the mistakes possibility in the medicinal plants offered in the perfumeries is undeniable. Therefore, the study on the other plant species in the perfumeries by the DNA barcoding method could be recommended as a necessity.

DNA barcoding is a new term introduced in to scientific literatures by Hebert and coworkers almost a decade ago (1). The concept of barcoding alone is well-known to the public: a series of black bars printed on many commercial products (1-3) (Universal Product Code), which are used to distinguish different products. Advances made in molecular biology and molecular techniques late 20th century e.g. sequencing technologies, has inspired scientists to apply barcoding concept to all domains of life by using the unique nature of DNA for each single species, in order to generate a comprehensive library of living organisms on the planet earth (2, 6). Such an ambitious initiative would result in a global DNA barcode database which will be valuable for biological scientists, medical, governmental and legal agencies as a mean of identification (1).

DNA barcoding based on a standardized region of 648 base pairs of mitochondrial DNA sequences from Cytochrome C Oxidase 1 (COX1) is proposed for animal species identification. Recent studies suggested that DNA barcoding has been effective for identifying 94% of bird species. The proposed threshold of 10 times the average intraspecific variation could be used for the identification and delimitation of new species. As a different part of the mitochondrial DNA evolves at various mutation rates, they show a variety of capabilities to distinguish taxa to species level. In order to compare the efficiency of protein-coding genes (PCGs) in birds, the complete genome of 310 birds, including 12 mitochondrial genes (except ND6) and barcoding the region of COX1, were examined. We concentrated on the intra- and inter-specific variations and the degree of mutational saturation as criteria for our evaluations. Some genes like ATP8, ND2 and ND5 showed the greatest divergence in intra- and inter-specific variations. The overlap between intra- and inter-specific variability for all genes is still troublesome. Our results may have been influenced by the sample size because our data were not representative of all bird species. More additional taxa may shed light more on DNA barcoding candidate genes.

Although polychaetes are the most abundant organisms in marine ecosystems, still their genetic diversity is understood inadequately. In this study, molecular identification of Nereididae polychaetes was performed by sequencing a segment of mitochondrial COI gene, isolated from mitochondrial DNA, and comparing nucleotide divergence, Molecular taxonomy, interspecific and intraspecific relations of Nereid species among 4 intertidal stations assigned in Persian Gulf of Iran. Analysis of 109 identified specimens, revealed 78 provisional gene sequences, related to 9 species and 6 genera, in which interspecific divergence was 1. 4 times higher than intraspecific divergence (2. 82% versus 1. 95%). The average pairwise sequence divergence for all sequences was estimated at 1. 37%. In three cases maximum divergence within a lineage exceeded the minimum nearest-neighbor distance: Perinereis sp., Platynereis sp. and Platynereis bicanaliculata. Maximum species similarity was observed amongst 3 sampling sites assigned in Bushehr Province whilst Bandar Abbas`s specimens showed less similarity to Bushehr station. Out of the 109 COI gene sequences of Nereididae polychaetes in this study, 34 contained multiple lineages. These results support the assertion that many Nereid populations in the Persian Gulf previously thought of as a single species, actually consist of two or more divergent lineages.