High gene flow maintains genetic diversity following selection for high EPSPS copy number in the weed kochia (Amaranthaceae)

Abstract

Kochia, a major weed species, has evolved resistance to four herbicide modes of action. Herbicide resistance appears to spread quickly, which could result in diminished standing genetic variation, reducing the ability of populations to adapt further. Here we used double digest restriction enzyme associated sequencing to determine the level of gene flow among kochia populations and whether selection for glyphosate resistance reduces genetic variation. Canadian Prairie populations show little to no genetic differentiation (FST = 0.01) and no correlation between genetic and geographic distance (r2 = − 0.02 p = 0.56), indicating high gene flow and no population structure. There is some evidence that kochia populations are genetically depauperate compared to other weed species, but genetic diversity did not differ between glyphosate susceptible and resistant populations or individuals. The inbreeding coefficients suggest there are 23% fewer heterozygotes in these populations than expected with random mating, and no variation was found within the chloroplast. These results indicate that any alleles for herbicide resistance can be expected to spread quickly through kochia populations, but there is little evidence this spread will reduce the species’ genetic variation or limit the species’ ability to respond to further selection pressure.

Genetic Diversity and Population Structure Revealed by SSR Markers on Endemic Species Osmanthusserrulatus Rehder from Southwestern Sichuan Basin, China

“…The mating system, that is, functional androdioecy, and the contrasting levels of gene flow might explain the high genetic diversity of this narrowly distributed species in some way [44,45]. The presence of null and dropout alleles will lead to a high deviation between Ho and He, and a high frequency of null alleles will cause the deviation from HWE in all loci [42,46].…”

“…In general, the genetic diversity of plants is positively correlated to the geographical range and population size, and the population decline leads to a loss of genetic diversity [43,45,48]. Endangered, endemic and narrowly distributed species usually have low genetic diversity, but many studies have shown that even endangered plants can have a moderate or high level of genetic diversity, such as Michelia coriacea Hung T. Chang & B. L. Chen (He = 0.505) [49], Rhododendron jingangshanicum P. C. Tam (He = 0.642) [50], Houpoea officinalis (Rehder & E. H. Wilson) N. H. Xia & C. Y. Wu (He = 0.600, I = 1.158) [51], Populus wulianensis S. B. Liang & X. W. Li (He = 0.611, I = 1.114, PPL = 98.6%) [26], Pteroceltis tatarinowii Maxim.…”

Herbicide diagnostics reveal multiple patterns of synthetic auxin resistance in kochia (Bassia scoparia)

“…The plants are heat, drought, and saline tolerant (Friesen et al 2009). Protogynous flowering aids in cross-pollination resulting in the transfer of herbicide resistance traits, and populations maintain high genetic diversity within and among fields (Beckie et al 2016;Martin et al 2020). In the fall, the stem abscises resulting in a tumbleweed that can disperse seeds among multiple fields within a single year.…”

Genomic‐based epidemiology reveals independent origins and gene flow of glyphosate resistance in Bassia scoparia populations across North America

“…gene duplication, gene flow, herbicide resistance, independent evolution, mobile genetic elements, population genetics the semi-arid arable lands of the western USA and Canada (Friesen et al, 2009). Kochia populations from North America exhibit high levels of genetic diversity but a lack of strong population structure (Kumar et al, 2019;Martin et al, 2020;Mengistu & Messersmith, 2002), probably due to several reproductive traits that promote cross-pollination and long-range dispersal of pollen and seed (Beckie et al, 2016).…”