Water and soil salinity as the main abiotic stresses decrease crop yield and restrict the use of agricultural lands. In order to assess salt stress effect on seedling growth of rice and to select more tolerant rice genotypes, a factorial experiment was performed at two levels of NaCl namely non-stress (EC 1.2 dS m −1 ) and salt-stress (EC 10 dS m −1 ) in hydroponics with an international rice collection consisted of 155 varieties. Seven stress tolerance indices including STI, SSI, HM, RDI, SSPI, ATI and TOL were used to identify salt tolerant genotypes. The results of variance analysis showed that the effect of genotypes (G), Salt treatment (T) and G×T interaction were significant for all investigated traits (except for the effect of genotypes on shoot length). Under salt stress most genotypes showed similar trend of salt response, i.e. reduction in all traits. The results also revealed that dry weight (DW) was less affected than fresh weight (FW), and the shoot weight (SW) was affected more than the root weight (RW), indicating that shoot growth is more sensitive than root growth to salt stress. The Na + , K + and Na + :K + ratio were increased more than 713%, reduced 22% and increased more than 996% under salt stress, respectively. Four stress tolerance indices including MP, HM, GMP and STI showed highest correlation with each other and also with plant performance (Z-scores) under both normal and stress conditions; thus each of these indices can be used as the suitable indicators for screening salt tolerant genotypes. Based on the results, genotypes #84, #30 and #48 showed the highest performance and STI under salinity condition, so they have considerable potential to improve salt tolerance in rice breeding programs. In addition, genotypes #178, #198 and #6 with the lowest values of STI were found to be intolerant genotypes to salt stress.

Background: The prevalence of Brucella infections in animals and humans has indicated the important need for different regional/local reference laboratories to use valid species-determining approaches to facilitate and compare data exchange. The purpose of current study was to evaluate the RNA Polymerase Beta Subunit (rpoB) as a molecular marker in Brucella species differentiation and to determine the genotype of Brucella melitensis species using single-nucleotide polymorphism (SNP) analysis. Materials & Methods: In this study, blood and cerebrospinal fluid (CSF) samples were taken from 108 patients with brucellosis. After culturing the samples insupplemented Brucella agar, eleven isolates of Brucella bacteria were isolated and identified by classical and molecular biotyping methods. Then the complete sequence of their rpoB gene was multiplied and sequenced. Sequencing results were analyzed by Mega6 program. Results: According to the results, the rpoB gene was able to differentiate between Brucella species and other bacteria.Moreover, the rpoB typing grouped the majority of Iranian isolates in the rpoB type 2, while only one strain belonged to the rpoB type 1. Among the 10 isolates of rpoB type 2, there are six different isolates with only one unique type-2 SNPs in codon 985, which gives rise to new genotype 2 variants. Conclusion: Our results shown a high discriminative power of rpoB gene among B. melitensis strains from some regions of Iran, which leads to accurate genotype and identification of these bacteria.

Background: RNA polymerase beta subunit (rpoB) gene analysis in bacterial communities is known as a method for determining rifampin sensitivity and genetic diversity among Brucella spp. Detection of antibiotic resistance among Brucella isolates can be a critical approach to control brucellosis. However, rpoB gene analysis of Brucella melitensis for assessing rifampicin resistance has not yet been performed in Iran, which is considered an endemic area for brucellosis. Objectives: The aim of this study was to analyze the whole sequence of rpoB genes of different B. melitensis isolates from humans to identify the single-nucleotide polymorphisms (SNPs) and mutations related to rifampin resistance and to analyze the genetic diversity of these bacteria in Iran. Methods: Between 2017 and 2019, a total of 156 blood samples along with 12 synovial fluid specimens were collected from brucellosis patients in different Iranian provinces and subjected to bacterial culture in Brucella selective media. Brucella identification was carried out using classical biotyping and molecular examinations. Polymerase chain reaction (PCR)-based amplification of the rpoB gene was performed by specific rpoB primers for whole gene sequencing. The antimicrobial susceptibility of Brucella isolates was assessed using disk diffusion susceptibility tests and minimal inhibitory concentration (MIC) methods. The presence of rifampin-binding sites and SNPs were investigated through rpoB whole gene sequencing. Results: Clinical B. melitensis isolates were obtained from blood (13) and synovial fluid (1) samples of patients from different regions of Iran. The results of MIC and disk diffusion susceptibility tests showed that all the isolates were sensitive to rifampin except for one isolate showing intermediate rifampin resistance based on the standards defined for slow-growing bacteria by the Clinical and Laboratory Standards Institute (CLSI). Gene analysis for identifying the mutations related to rifampin resistance and investigating genetic diversity showed that none of the B. melitensis isolates had missense mutations, confirming the susceptibility of all the studied isolates to rifampin. Conclusions: The present study revealed that rpoB gene analysis could be used for the efficient and precise identifying of the mutations related to rifampin resistance, investigating rifampin binding sites, and genotyping Brucella species. Furthermore, the identification of B. melitensis isolates with intermediate resistance to rifampicin highlighted the importance of periodically carrying out antibiotic susceptibility testing. The molecular detection of rpoB mutations in different Brucella isolates may help to prevent the spread of rifampin-resistant Brucella spp. among humans and livestock.