AUTHOR=Bracamonte Enzo R. , Fernández-Moreno Pablo T. , Bastida Fernando , Osuna María D. , Alcántara-de la Cruz Ricardo , Cruz-Hipolito Hugo E. , De Prado Rafael 

TITLE=Identifying Chloris Species from Cuban Citrus Orchards and Determining Their Glyphosate-Resistance Status

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01977

DOI=10.3389/fpls.2017.01977

ISSN=1664-462X

ABSTRACT=<p>The <italic>Chloris</italic> genus is a C<sub>4</sub> photosynthetic species mainly distributed in tropical and subtropical regions. Populations of three <italic>Chloris</italic> species occurring in citrus orchards from central Cuba, under long history glyphosate-based weed management, were studied for glyphosate-resistant status by characterizing their herbicide resistance/tolerance mechanisms. Morphological and molecular analyses allowed these species to be identified as <italic>C. ciliata</italic> Sw., <italic>Chloris elata</italic> Desv., and <italic>Chloris barbata</italic> Sw. Based on the glyphosate rate that causes 50% mortality of the treated plants, glyphosate resistance (R) was confirmed only in <italic>C. elata</italic>, The R population was 6.1-fold more resistant compared to the susceptible (S) population. In addition, R plants of <italic>C. elata</italic> accumulated 4.6-fold less shikimate after glyphosate application than S plants. Meanwhile, populations of <italic>C. barbata</italic> and <italic>C. ciliata</italic> with or without glyphosate application histories showed similar LD<sub>50</sub> values and shikimic acid accumulation rates, demonstrating that resistance to glyphosate have not evolved in these species. Plants of R and S populations of <italic>C. elata</italic> differed in <sup>14</sup>C-glyphosate absorption and translocation. The R population exhibited 27.3-fold greater 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) activity than the S population due to a target site mutation corresponding to a Pro-106-Ser substitution found in the EPSPS gene. These reports show the innate tolerance to glyphosate of <italic>C. barbata</italic> and <italic>C. ciliata</italic>, and confirm the resistance of <italic>C. elata</italic> to this herbicide, showing that both non-target site and target-site mechanisms are involved in its resistance to glyphosate. This is the first case of herbicide resistance in Cuba.</p>