Abstract: The genetic diversity and genetic structure of 18 Galinsoga quadriradiata populations in China were analyzed by intersimple sequence repeat (ISSR), to lay a foundation for its control. The results showed that 10 primer groups were screened and 349 loci were gotten by ISSR marker analysis. Analyzed by Popgene software, the percentage of polymorphic loci (P) was 8.88%-29.51%, the Nei’s gene diversity index (H) among populations was 0.0248-0.1023, coefficient of gene differentiation (G_st) among populations was 0.4663, gene flow (N_m) among populations was 0.5723, genetic similarity among populations was 0.9404 and genetic distance among populations was 0.0621. The 18 G. quadriradiata populations were clustered into 5 groups by UPGMA cluster analysis. The Mantel test suggested that there was no significant correlation between the genetic distance and geographic distance of different G. quadriradiata populations. In summary, our results suggested that there existed a lower level of genetic diversity and higher level of genetic differentiation of G. quadriradiata populations. The spread of G. quadriradiata in the studied regions was mainly attributed to the events of humanmediated longdistance and repeated multiple dispersal of seeds.

Key words: alternate subsurface drip irrigation, water consumption characteristics, water use efficiency., spring maize, yield