Genetic diversity and geographic dispersion in Thymus spp. as detected by RAPD markers

Thyme, as an aromatic medicinal plant and a perennial and woody herb Lamiaceae has commercial, pharmaceutical and perfumery potentialities. Thymus is taxonomically a very complex genus with high frequency of hybridization and introgression among sympatric species, and some species of this herb are endemic to Iran. From the chemical point of view, important biochemical components such as thymol and carvacrol are known in thyme. In the present study, 13 Thymus spp. accessories collected from different geographic areas of Iran along with one accession from England (Thymus vulgaris) were analyzed by Random Amplified Polymorphic DNA (RAPD) markers using 20 primers to discover genetic polymorphism. A total number of 510 bands were detected from 20 RAPD primers, of which 483 (94.315) were polymorphic with an average of 24.15 polymorphic bands per primer. The size range of the amplified products was 200-4000 bp. UPGMA cluster analysis was carried out using Jaccard similarity coefficients based on PAPDS. The dendrogram obtained from the method classifies the 14 thymes accessions into four major groups. Scatter biplot based on principal coordinate analysis (PCoA) also revealed four groups and confirmed the results of clustering method with some minor disagreements. The accessions were relatively grouped according to the location where they had been collected. The molecular variation assessed in the study could elucidate largely geographic dispersion of the thyme accessions, and in combination with biochemical characteristics, can be useful to improve the efficiency of selection and breeding programs

Identification of Fusarium Head Blight Resistance QTLs in a Wheat Population Using SSR Markers

Fusarium head blight (FHB) caused by Fusarium graminearum is a destructive disease of wheat. Breeding for FHB resistance by conventional breeding methods is feasible but laborious and expensive. Detection of DNA markers associated with FHB resistance quantitative tract loci (QTL) will accelerate breeding programs. This study was conducted to identify simple sequence repeat (SSR) markers linked FHB resistance QTLs in wheat. A population of 167 F ₂:₃ from the cross Wangshuibai (resistant)/Falat (suspectible) was used. The Type II resistance (spread by pathogen within a spike) was evaluated on F₃ families derived from F₂ plants in the greenhouse. Two QTLs were detected that together explained 25.1% of the phenotypic variation. A QTL region on chromosome 3B explained 16% of the variation. Additional QTL was located on chromosomes 2A accounting for 9.1% of the phenotypic variation