<b>Genetic admixture in species of <i>Conyza</i> (Asteraceae) as revealed by microsatellite markers

Abstract

ABSTRACT. The distinction among Conyza canadensis, C. bonariensis, and C. sumatrensis is a challenge for weed science. In the current study, primers for microsatellite (SSR) loci were used to investigate the molecular divergence among the three species, the genetic structure of the populations at the molecular level and the level of genetic admixture among Conyza plants from southern Brazil. Twelve primers amplified well-defined DNA segments for all 88 samples of the three Conyza species. The estimated proportion of SSR polymorphic loci, number of alleles, and mean expected heterozygosity were higher in samples of C. bonariensis than in samples of C. sumatrensis or C. canadensis. Conyza canadensis was the species with the lowest molecular diversity. High genetic divergence was observed among the three species. The well-defined ancestral groups for each species led to the identification of samples of Conyza with ancestral genomes from the three species. Hybridization events between pairs of these species may have occurred in crop fields from southern Brazil. The high molecular diversity in resistant biotypes of C. sumatrensis indicated that these biotypes have a high potential to colonize new areas, which increases its potential as a weed.Keywords: horseweed, molecular divergence, SSR loci.Mistura genética em espécies de Conyza (Asteraceae) reveladas por marcadores microsatélites RESUMO. A identificação das espécies Conyza canadensis, C. bonariensis e C. sumatrensis tem sido desafiadora para a ciência das plantas daninhas. No presente estudo, primers para locos microssatélites (SSR) foram utilizados para investigar a divergência molecular entre as três espécies; mostrar como as populações estão geneticamente estruturadas em nível molecular e avaliar o nível de mistura genética entre as plantas de Conyza no Sul do Brazil. Doze primers amplificaram segmentos de DNA bem definidos em todas as 88 amostras das três espécies. A proporção estimada de locos SSR polimórficos, o número de alelos, e a heterozigosidade média esperada foram mais altos nas amostras de C. banariensis do que nas demais. C. canadensis foi a espécie com menor diversidade molecular. Divergência genética alta foi observada entre as três espécies. A formação de grupos ancestrais bem definidos para cada espécie levou à identificação de amostras de Conyza com genoma ancestral das três espécies. A ocorrência de hibridização entre as três espécies pode ter ocorrido nas lavouras do Sul do Brasil. A diversidade molecular alta em biótipos resistentes de C. sumatrensis indicou que estes biótipos têm um alto potencial para colonizar novas áreas, o que agrava seu potencial como planta daninha.Palavras-chave: buva, divergência molecular, locos SSR.

Glyphosate Applied at the Early Reproductive Stage Impairs Seed Production of Glyphosate-Resistant Hairy Fleabane

“…The species C. bonariensis was used. The identification of the species was performed by genotyping using SSR (simple sequence repeats) molecular markers, according to Abercrombie et al (2009) and Marochio et al (2017) (Piasecki et al 2019a;Piasecki et al 2019b).…”

Spread of glyphosate‐resistant sourgrass (Digitaria insularis): Independent selections or merely propagule dissemination?

“…The independent selection of herbicide‐resistant populations is usually more frequent for self‐pollinating species than for cross‐pollinating species because gene flow in autogamous species is lower (Ng et al ) and their dissemination to new areas depends on the movement of seeds or other reproductive structures, such as rhizomes. Although there is no information about sourgrass crossing type, this study’s data demonstrates low levels of genetic diversity in all populations, which is a typical characteristic of self‐pollinated species (Ward & Jasieniuk ; Marochio et al ), suggesting that sourgrass has low cross‐pollination rate.…”

Genetic Dissimilarity in Conyza sumatrensis Revealed by Simple Sequence Repeat (SSR) Markers

“…Moreover, the occurrence of an unfavorable event can eliminate all susceptible individuals and allow survival of the resistant weeds (Kissmann, 2003). C. sumatrensis showed high molecular diversity in resistant biotypes, indicating that these biotypes have a high potential to colonize new areas, which increases its potential as a weed (Marochio et al, 2017).…”

“…Research on Conyza spp. was carried out with the objective of obtaining information on the evolution, origin and dispersion of the resistance of the species to glyphosate herbicide (Ren et al, 2010;Okada et al, 2013;Okada et al, 2014;Marochio et al, 2017). In these studies, analysis of the microsatellite markers was based on the presence of multiple alleles per locus favoring the genetic diversity among populations and subpopulations, as is the case of most weeds (Zhang et al, 2009), thereby contributing to management strategies for these plants.…”