Genetic diversity of the annual weed Monochoria vaginalis in southern China detected by random amplified polymorphic DNA and inter-simple sequence repeat analyses

Two molecular genetic screening techniques, RAPD (random amplified polymorphic DNAs) and ISSR (inter-simple sequence repeats), were applied to detect the level and pattern of genetic diversity of Monochoria vaginalis, a common weed of rice fields, in seven populations from southern China. Among these populations, 116 bands were amplified by 18 RAPD primers, of which 34 bands (29.31%) were polymorphic, and 14 ISSR primers produced 111 bands with 87 polymorphic bands (78.38%). Within each population, a relatively low level of genetic diversity was detected by both RAPD and ISSR analyses, with a mean genetic diversity (H) of 0.0348 and 0.0551 respectively. Analysis of molecular variance of the data from the RAPD and ISSR markers detected that the majority of total genetic variation existed among populations (73.50% and 76.70% respectively) and only minor genetic variation within populations (26.50% and 23.30% respectively). Cluster analysis divided the seven populations into two groups, indicating that the genetic relationships among populations have relatively low correlation with their geographical distribution (Mantel test; r = 0.45 and 0.48 respectively). Our results indicated that both RAPD and ISSR markers were effective and reliable for accurately assessing the degree of genetic variation of M. vaginalis. Comparing the two techniques, ISSR markers were more efficient than the RAPD assay. The Mantel test gave r = 0.16, suggesting no correlation between these two molecular markers.