The Study On Genetic Diversity And Differentiation Of Invasive Plant Galinsoga Quadriradiata Populations In China

Galinsoga quadriradiata, a Galinsoga species of Compositae, is native to South America, one of an invasive species which has already widely distributed in China. This exotoc invasive plant has a high level of ecological suitability. It can survive and develop in different environmental conditions, which results in serious threat to farmland, forestry, greenbelt, etc. It has become one of the malignant weeds to be controlled in China. The genetic diversity and genetic structure of G. quadriradiata populations within the 18 populations in China were analyzed by inter-simple sequence repeat(ISSR) from. The genetic diversiy and differentiation of Galinsoga parviflora and G. quadriradiata in 7 populations of the same geographic were compared by using the same method. The two species were used to analyze their chromosome number and karyotype by applying root tip squash method. Aimed to explore the mechanism of its invasion from genetic and cytology level, and it will lay the foundation for its control strategy. The main conclusions were as follows:1. The genetic diversity and genetic structure of 18 G. quadriradiata populations in China were analyzed by inter-simple sequence repeat(ISSR). The results showed that diversity levels of popoulations were relatively high, mean percentage of polymorphic loci(P) was 18.39%, mean Nei’s gene diversity index(H) among populations was 0.0604, and mean Shannon index(I) was 0.0923. Coefficient of gene differentiation(Gst=0.4663) showed a high differentiation among populations. The main source of genetic variance was among individuals within population. At the genetic similarity among populations was 0.9404, the 18 G. quadriradiata populations were clustered into 5 groups by UPGMA cluster analysis, which correspond with their geographic regions. The Mantel test suggested that there was no significant correlation between the genetic distance and geographic distance of different G. quadriradiata populations.2. The genetic diversity and differentiation of G. quadriradiata and G. parviflora populations were compared by ISSR. The results showed that the genetic diversity of G. quadriradiata(P=22.06%,H=0.0748,I=0.1133) was lower than that of G. parviflora(P=35.18%,H=0.1111,I=0.1721), and the genetic differentiation among G. quadriradiata populations(Gst=0.4356) was significantly higher than G. parviflora(Gst=0.2518), and the main source of genetic variance was among individuals within population. At the genetic similarity among populations was 0.9550, cluster analysis based on the UPGMA method grouped the majority of 7 G. parviflora and G. quadriradiata populations into 4 groups respectively, which correspond with the geographic distribution of G. quadriradiata populations, but not with G. parviflora. The Mantel test indicated that there was no significant correlation between the genetic distance and geographic distance both of the two species.3. The seeds of G. quadriradiata and G. parviflora were used to analyze their chromosome number, ploidy and karyotype respectively by root tip squash method. The results showed that both G. quadriradiata and G. parviflora were diploid and metacentric, chromosome number in the two species were 2n=32 and 2n=16, their coefficients of karyotype asymmetry were 55.78% and 57.4%. The karyotype formulaes were as follows: G. quadriradiata 2n=2x=32=30m+2sm, G. parviflora 2n=2x=16=14m+2sm and which belonged to Stebbins’ 2A type and 1A type. The karyotype of the two species was similar to that of the primitive plants.