Genetic variation within and among 12 populations of whip grass in south China were investigated using inter-simple sequence repeat (ISSR) and sequence-related amplified polymorphism (SRAP). High genetic diversity was found in whipgrass by two molecular makers (PPB=86.21%, I=0.357 based on ISSR; PPB=82.21%, I=0.352 based on SRAP). However, there was relatively low genetic diversity at population levels. A high degree of genetic differentiation among populations was detected based on different measures and different molecular markers. We also found that SRAP markers were more efficient than ISSR markers in this species. Based on these findings, sampling strategy was proposed for successfully utilizing the genetic resource of this species.

Phylogenetic relationships among 53 accessions of D.glomerata collected from 5 continents were investigated using simple sequence repeat (SSR) markers. 15 SSR primer pairs generated a total of 127 alleles, with an average of 8.5 alleles per locus. The average polymorphic rate (P) was 95.21 %. The genetic similarity (GS) among all accessions ranged from 0.43 to 0.94, with an average of 0.63. Analysis of molecular variance (AMOVA) indicated that larger proportions of variability existed within geographical regions (73.75%). High degree of genetic diversity was observed in Asia (P, 90.55%) and Europe (P, 86.61%) groups. Based on the cluster and principal component analysis, 53 accessions could be divided into five groups (GS=0.64) according to the nearest phylogenetic relationship.

SRAP (Sequence-related amplified polymorphism) and ISSR (Inter simple sequence repeat) molecualr markers were used to evaluate the levels and patterns of genetic diversity among 45 collections of orchardgrass from four continents. Twenty-one primer combinations were used and 480 bands were produced in SRAP, of which 405(84.38%) were polymorphic. On the other hand, twelve primers were used to generate a total of 116 bands in ISSR, of which 116(87.07%) were polymorphic. The coefficient range of genetic similarity was 0.6248-0.9686 and 0.6116-0.9231 respectively. Based on cluster and principal component analysis on the genetic characteristics, all collections could be divided into four groups and five groups in two markers, respectively. According to the analysis of genetic diversity and relationships, the appropriate strategies for collection and conservation of germplasm resources also were discussed and scientific breeding with far genetic relationship materials in orchardgrass were suggested.