Glyphosate Resistance in a Johnsongrass (Sorghum halepense) Biotype from Arkansas

Abstract

Johnsongrass is one of the most troublesome weeds of the world and is listed as a noxious weed in Arkansas. Reduced johnsongrass control with the recommended application rate of glyphosate (840 g ae ha−1) was reported in a continuous soybean field near West Memphis, AR, in the fall of 2007. A greenhouse study was conducted (1) to confirm and characterize glyphosate resistance in the johnsongrass biotype from West Memphis and (2) to determine whether resistant and susceptible biotypes have differential glyphosate absorption or translocation. Dose–response studies revealed that the resistant biotype was five- to seven-fold less sensitive to glyphosate than the susceptible biotype. Glyphosate absorption was similar in resistant and susceptible biotypes at 72 h after treatment (HAT). However, the treated leaf of the resistant biotype retained 28 percentage points more absorbed14C glyphosate compared to the susceptible biotype at 72 HAT. Additionally, the resistant biotype had less14C glyphosate translocated to the aboveground tissue below the treated leaf and to roots compared to the susceptible biotype at 24 and 72 HAT. Reduced translocation and increased retention of glyphosate in treated leaves is a probable mechanism of resistance in this glyphosate-resistant johnsongrass biotype.

Assessment of Weed Management Practices and Problem Weeds in the Midsouth United States—Soybean: A Consultant's Perspective

“…Although johnsongrass [Sorghum halepense (L.) Pers.] was not ranked among the top five problematic weeds, it was ranked second overall based on importance in the midsouth, which might be due to its widespread occurrence along roads and field borders in the midsouth region (M. V. Bagavathiannan, unpublished data) and the recent evolution of glyphosate-resistant johnsongrass biotype in Arkansas, Mississippi, and Louisiana (Heap 2012;Riar et al 2011b).…”

De Novo Genome Assembly of the Economically Important Weed Horseweed Using Integrated Data from Multiple Sequencing Platforms

“…This is the case with the many biotypes of glyphosate-resistant horseweed as well as several other glyphosate-resistant weedy plant species, such as johnsongrass (Sorghum halepense), ryegrass (Lolium spp. ), velvet bean (Mucuna pruriens), and wild radish (Raphanus raphanistrum; Mueller et al, 2003;Feng et al, 2004;Main et al, 2004;Zelaya et al, 2004;Koger and Reddy, 2005;Owen and Zelaya 2005;Preston and Wakelin, 2008;Ge et al, 2010Ge et al, , 2012Riar et al, 2011;Rojano-Delgado et al, 2012;Vila-Aiub et al, 2012;Ashworth et al, 2014;Sammons and Gaines, 2014). Physiologically, we know that non-target-site resistance can involve a plethora of metabolic, conversion, sequestration, and reduced translocation processes, including oxidation, conjugation, or compartmentation of the herbicide molecules (Yuan et al, 2007;Cummins et al, 2013;Iwakami et al, 2014).…”

Distribution of Arable Weed Populations along Eastern Arkansas–Mississippi Delta Roadsides: Factors Affecting Weed Occurrence

“…All of these effects are critically important given the increase in glyphosate-resistant weed species such as Palmer amaranth, johnsongrass, giant ragweed (Ambrosia trifida L.), and goosegrass [Eleusine indica (L.) Gaertn.] throughout the midsouthern United States (Green and Owen 2011;Heap 2014;Osunsami 2009;Reddy and Norsworthy 2010;Riar et al 2011;Shaner 2000). Therefore, understanding the dominant routes, mechanisms, and rates of weed spread across landscapes is of utmost importance for preventing the spatial weed infestation and subsequent spread of herbicide-resistant biotypes.…”