Genetic Diversity and Population Structure of Bermudagrass [Cynodon dactylon (L.) Pers.] along Latitudinal Gradients and the Relationship with Polyploidy Level

Abstract

Understanding the population genetic pattern and process of gene flow requires a detailed knowledge of how landscape characteristics structure populations. Although Cynodon dactylon (L.) Pers. (common bermudagrass) is widely distributed in the world, information on its genetic pattern and population structure along latitudinal gradients is limited. We tried to estimate the genetic diversity and genetic structure of C. dactylon along a latitudinal gradient across China. Genetic diversity among different ploidy levels was also compared in the study. The material used consisted of 296 C. dactylon individuals sampled from 16 geographic sites from 22°35′ N to 36°18′ N. Genetic diversity was estimated using 153 expressed sequence tag-derived simple sequence repeat (EST-SSR) loci. Higher within-population genetic diversity appeared at low-latitude, as well as having positive correlation with temperature and precipitation. The genetic diversity increased with the ploidy level of C. dactylon, suggesting polyploidy creates higher genetic diversity. No isolation by distance and notable admixture structure existed among populations along latitudes. Both seed dispersal (or vegetative organs) and extrinsic pollen played important roles for gene flow in shaping the spatial admixture population structure of C. dactylon along latitudes. In addition, populations were separated into three clusters according to ploidy levels. C. dactylon has many such biological characters of perennial growth, wind-pollination, polyploidy, low genetic differentiation among populations, sexual and asexual reproduction leading to higher genetic diversity, which gives it strong adaptability with its genetic patterns being very complex across all the sampled latitudes. The findings of this study are related to landscape population evolution, polyploidy speciation, preservation, and use of bermudagrass breeding.

Diversity Patterns of Bermuda Grass along Latitudinal Gradients at Different Temperatures in Southeastern China

“…Greater intraspecific genetic variation, based on our analysis of molecular variance (AMOVA), could confer a competitive advantage in a changing environment. These results agree with the published results of our analysis of the genetic structure using expressed sequence tag-derived simple sequence repeats (EST-SSR) [ 29 ]. Higher environmental heterogeneity could favor higher tolerance of environmental factors and a broader range of acclimation responses [ 30 , 31 ].…”

“…The results of both the genetic structure analysis and the PCA analysis corresponded to growth habits [ 32 , 33 , 34 ]. Migration among different populations was assumed in our structure analyses, while gene flow could have caused populations at different latitudes to adapt to similar conditions, which has been well-researched [ 29 ]. Proposed adaptive introgression could allow for adaptation and establishment in different environmental conditions [ 35 ].…”

Non-linear genetic diversity and notable population differentiation caused by low gene flow of bermudagrass [Cynodon dactylon(L.) Pers.] along longitude gradients

“…The 20 EST-SSR primer pairs from previous research (Zhang et al, 2019) produced clear and polymorphic bands and were subsequently used to evaluate genetic diversity for this study. 25 µL PCR amplifications reaction solution contains 1 µL of template DNA, 2.5 µL 10× PCR buffer, 2 µL of 25 mM MgCl 2 , 0.5 µL of 10 mM deoxy nucleoside triphos phate (dNTP), 0.5 µL each of forward and reverse primers, 0.2 µL of Taq DNA polymerase, and 17.8 µL of nuclease-free water.…”

“…The amplifications were performed with the following PCR protocol used in the previous research (Zhang et al, 2019): first 1 cycle of 3 min at 95 • C, followed by 10 cycles at 95 • C, 60 • C and 72 • C respectively for 30 s, finally terminating with 1 cycle of 6 min at 72 • C. Next, the samples were subjected to 1 cycle at 95 • C for 3 min, then 20 cycles of 30 s at 95 • C, 55 • C, and 72 • C respectively, and finally 1 cycle at 72 • C for 6 min. PCR amplified fragments labelled with one fluorescent tag (6-FAM (6-carboxyfluorescein) (blue) and HEX (green)) were detected on a 3730XL Genetic Analyzer (ABI, USA) with the size standard GS500 LIZ.…”

“…Although C. dactylon has important research value, the understanding of its population genetic structure and geographic variation is limited. Genetic diversity and genetic structure of C. dactylon along a latitudinal gradient across China and the relationship between genetic diversity and ploidy levels were also studied in our previous study (Zhang et al, 2019). Sampling includes maximum geographical variation from flooded east to arid west along the longitude to quantify the relative importance of longitude for adaptive genetic divergence of different bermudagrass populations.…”