Population Genetic structure and Salt Tolerance of Conyza canadensis in Korea

Abstract

Herbicides and other various managements to reduce the abundance of weed populations applied strong selection. The adaptation of weed populations to those conditions often makes difficulties in establishing effective management strategies. Conyza canadensis is an annual weed, known as introduced to Korea about 150 years ago. Conyza canadensis can live in a very harsh environment with high vitality and reproduction, which helps horseweed to threaten the domestic ecosystem. To obtain information on the management of Conyza canadensis in Korea, I investigated the population structure of 8 Conyza canadensis populations using microsatellite marker. And I confirmed the phenotypic variation among 8 Conyza canadensis populations from coastal and inland regions under NaCl condition to evaluate the salt tolerance. Then I tried to identify the correlation between results to suggest the evidence of coastal populations’ local adaptation. Populations are differentiated at a high level. The average genetic diversity of coastal populations was not lower than inland populations, but significantly different at the population level. I couldn’t find apparent structuring patterns on the genetic differentiation among the coastal populations using Bayesian clustering. However, only Ms population showed a high salt tolerance in measured traits among the coastal populations. Although the other coastal populations had a high tolerance in the electrical conductivity test, I couldn’t find evidence of local adaptation in other traits. Thus the genetic drift may be more substantial to the current pattern of differentiation than the natural selection. But we can’t ignore the influence of adaptive selection because Mc population also showed a high salt tolerance with low genetic diversity as Ms population while its habitat has a low salt concentration. Another environmental stress such as drought may give positive selection, but I couldn’t define it in this study. However, the adaptive potential of Conyza canadensis in Korea is high because of high genetic variation among populations. A further investigation must be carried to clarify the strength of genetic drift and natural selection in this case. Furthermore, future research must consider other environmental variables such as soil moisture or temperature fluctuation to understand the evolutionary history of Conyza canadensis in Korea and establish a successful management plan.