Genetic diversity and structure of Lolium perenne ssp. multiflorum in California vineyards and orchards indicate potential for spread of herbicide resistance via gene flow

Abstract

Management of agroecosystems with herbicides imposes strong selection pressures on weedy plants leading to the evolution of resistance against those herbicides. Resistance to glyphosate in populations of Lolium perenne L. ssp. multiflorum is increasingly common in California, USA, causing economic losses and the loss of effective management tools. To gain insights into the recent evolution of glyphosate resistance in L. perenne in perennial cropping systems of northwest California and to inform management, we investigated the frequency of glyphosate resistance and the genetic diversity and structure of 14 populations. The sampled populations contained frequencies of resistant plants ranging from 10% to 89%. Analyses of neutral genetic variation using microsatellite markers indicated very high genetic diversity within all populations regardless of resistance frequency. Genetic variation was distributed predominantly among individuals within populations rather than among populations or sampled counties, as would be expected for a wide‐ranging outcrossing weed species. Bayesian clustering analysis provided evidence of population structuring with extensive admixture between two genetic clusters or gene pools. High genetic diversity and admixture, and low differentiation between populations, strongly suggest the potential for spread of resistance through gene flow and the need for management that limits seed and pollen dispersal in L. perenne.

Determination of Morphological and Genetic Diversity of ALS (Acetolactate Synthase)- Herbicide-Resistant Echinochloa oryzoides Biotypes in Rice

“…Studies on morphological and genetic diversity are important in terms of developing an understanding of how both herbicides and environmental influences affect weed species (Sterling et al, 2004;Claerhout et al, 2015;Karn and Jasieniuk, 2017). Through statistical evaluations based on population genetic structure and quantitative characteristics, the study clearly demonstrates morphological similarities and genetical distances of E. oryzoides populations.…”

“…In addition, the genetic relationships among genotypes were represented using a PCA (Backhaus et al, 1989) analysis with SPSS 21.0 software (IBM Crop. Armonk, NY: USA Released 2012) (Juraimi et al, 2005;Vilatersana et al, 2005;Santaella et al, 2006;Lee et al, 2014;Claerhout et al, 2015;Karn and Jasieniuk, 2017).…”

“…Natural selection, genetic flow and genetic drift are the forces that cause an evolution in both the natural environments and weeds (Vigueira et al, 2013). Many weed species display differences in terms of their genetic characteristics due to different growth patterns and morphological characteristics, depending on the area in which they grow (Yabuno, 1996;Michishita and Yamaguchi, 2003;Claerhout et al, 2015;Karn and Jasieniuk, 2017). The sizes of resistant populations give rise to high genetic diversity within a species in a region by accumulating mutations over time (Karn and Jasieniuk, 2017).…”

“…Many weed species display differences in terms of their genetic characteristics due to different growth patterns and morphological characteristics, depending on the area in which they grow (Yabuno, 1996;Michishita and Yamaguchi, 2003;Claerhout et al, 2015;Karn and Jasieniuk, 2017). The sizes of resistant populations give rise to high genetic diversity within a species in a region by accumulating mutations over time (Karn and Jasieniuk, 2017). In addition, key occurrences during the propagation of resistance, such as local mutation and selection pressure, and intra-population pollen and seed dispersal, have led to the formation of regional genetic variations throughout the agricultural landscape.…”

“…Herbicide-resistance evolution in the susceptible populations may be triggered due to high level of genetic diversity that supports the increase in the adaptation capacity of more durable species. Geographical location differences provide information on the pathway and mechanisms of resistance propagation (Menchari et al, 2007;Delye et al, 2010;Duhoux et al, 2017;Karn and Jasieniuk, 2017).…”