Identification of purple nutsedge (Cyperus rotundus L.) ecotypes and the effect of environmental factors on tuber sprouting in China

Purple nutsedge (Cyperus rotundus L.) is a widely distributed weed. To evaluate the effect of environmental factors on tuber sprouting in different ecotypes, an inter-simple sequence repeat (ISSR)-based genetic analysis approach was used to assess the genetic relatedness among 24 purple nutsedge populations collected in China. Twenty-one ISSR primers were selected to generate 167 scorable bands. The percentage of polymorphic bands (PPB) was 97%, indicating a high level of genetic diversity, and the cluster results largely coincided with the geographical locations. Three ecotypes, HN-1, HB-1 and SD-1 (collected from Hai'nan Island, central China and northern China, respectively), with large genetic and geographic distances from each other, were selected to assess variation in the purple nutsedge sprouting trait. Compared with the other ecotypes, ecotype SD-1 showed the highest sprouting capacity at constant 15 degrees C and at 10/20 degrees C, and the shortest time to reach 80% sprouting (t(80)) at constant 20 degrees C and at 15/25 and 20/30 degrees C. The sprouting percentage was very high (95%-98.8%) and without significant differences between the three ecotypes over a pH range between 5 and 9. The osmotic potentials that caused 50% inhibition of the maximum sprouting percentages of HN-1, HB-1 and SD-1 were -0.37, -0.43 and -0.44 MPa respectively. Ecotype SD-1 appeared to maintain a slightly higher sprouting percentage under osmotic stress, but the difference was not significant. These findings suggest that the higher tolerance to lower temperatures and drought of ecotype SD-1 might be an adaptation to lower winter temperature and drier climatic conditions in North China. Abundant genetic diversity may be a potential factor that endows purple nutsedge with strong environmental adaptability.