Genetic variation and clonal diversity of Psammochloa villosa (Poaceae) detected by ISSR markers

Genetic variation and clonal diversity of seven Psammochloa villosa (Poaceae) populations from northwest China were investigated using inter simple sequence repeat (ISSR) markers. Of the 84 primers screened, 12 produced highly reproducible ISSR bands. Using these primers, 173 discernible DNA fragments were generated with 122 (70.5%) being polymorphic, indicating considerable genetic variation at the species level. In contrast, there were relatively low levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 6.1 to 26.8. Analysis of molecular Variance (AMOVA) showed that a large proportion of genetic variation (87.46%) resided among populations, while only 12.54% resided among individuals within populations. Clonal diversity was also high with 98 genets being detected from among 157 individuals using 12 ISSR primers. The evenness of distribution of genotypes in P. villosa populations varied greatly, with all of the genotypes being local ones. No significant differences in genetic or clonal diversity were found between populations in mobile or fixed dunes. The main factor responsible for the high level of differentiation among populations and the low level of diversity within populations is probably the clonal nature of this species, although selfing may also affect the population genetic structure to some extent. The efficiency of ISSRs in identifying genetic individuals was much higher than that of allozymes. An approximately asymptotic correlation was found between the number of genets detected and the number of polymorphic loci used; suggesting that use of a high number of polymorphic bands is critical in genet identification. (C) 2001 Annals of Botany Company.