AUTHOR=Fernández-Moreno Pablo T. , Alcántara-de la Cruz Ricardo , Smeda Reid J. , De Prado Rafael 

TITLE=Differential Resistance Mechanisms to Glyphosate Result in Fitness Cost for Lolium perenne and L. multiflorum

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01796

DOI=10.3389/fpls.2017.01796

ISSN=1664-462X

ABSTRACT=<p>Multiple mechanisms of resistance to glyphosate are exhibited by populations of <italic>Lolium</italic> spp. worldwide. Association of resistance with growth and reproductive fitness is an important predictor for long-term success of glyphosate-resistant (R) versus glyphosate-susceptible (S) biotypes. Numerous studies were conducted on R- and S-biotypes of Italian ryegrass (<italic>Lolium multiflorum</italic>) and perennial ryegrass (<italic>L. perenne</italic>) to characterize the underlying mechanism(s) of glyphosate resistance and associate this with growth and reproductive fitness. <italic>L</italic>. <italic>perenne</italic> expressed both altered uptake and translocation as well as a genetic change at 106-Pro to –Ser, This pattern for two resistance mechanisms is unique. <italic>L. multiflorum</italic> also exhibited altered uptake and translocation as well as duplication of EPSPS gene copies. Reduced plant biomass and height for R-versus S-biotypes of both species was evident over two growing seasons. This resulted in S- versus R- <italic>L. multiflorum</italic> producing up to 47 and 38% more seeds in 2014 and 2015, respectively. S- <italic>L. perenne</italic> produced up to 20 and 30% more seeds in 2014 and 2015, respectively. Both non-target site and target-site mechanisms of glyphosate resistance can render <italic>Lolium</italic> spp. at a competitive disadvantage. This has long-term implications for the success of glyphosate-resistant plants in the absence of selection pressure.</p>