Variation in Response and Resistance to Glyphosate and Glufosinate in California Populations of Italian Ryegrass (Lolium perennessp.multiflorum)

Abstract

Reduced control of Italian ryegrass in California with herbicides has raised concerns about the evolution of populations with resistance to multiple herbicides. The goal of this study was to investigate variation among populations in plant response and resistance to glyphosate and glufosinate in Italian ryegrass from vineyards and orchards in northwest California. Population resistance screening using field-collected seed revealed up to 56.9% of individuals surviving glyphosate treatment at 1,678 g ae ha−1, and 53.5% of individuals surviving glufosinate treatment at 2,242 g ai ha−1in the same population. Frequencies of surviving plants within populations varied among screening times, particularly for glufosinate. Treating vegetatively propagated, genetically identical tillers with each herbicide pointed to separate mechanisms of resistance rather than cross-resistance to glyphosate and glufosinate. Dose–response experiments were conducted for each herbicide at two different screening times using a subset of populations, field-collected seed, and 10 herbicide rates. Plant survival and biomass were evaluated for each population at 3 wk after treatment and for plant regrowth 1 wk thereafter. Log-logistic regression models fit to the data were used to estimate LD50, GR50, and RD50values and calculate resistance indices (R/S ratios). Based on LD50values, the most highly resistant population was 14.4- to 19.2-fold more resistant to glyphosate than the most susceptible population tested but only 1.6- to 2.0-fold more resistant to glufosinate than the most susceptible population tested. Levels of resistance to both herbicides varied with screening time period and variable measured. Results indicate high frequencies of glyphosate-resistant plants but an early stage in the evolution of glufosinate resistance in some Italian ryegrass populations of northwest California.

Emergence of Glyphosate- and Glufosinate-resistant Italian Ryegrass (<i>Lolium multiflorum</i>) Populations in Japanese Pear Orchards in Japan and their Responses to Several Foliar-applied Herbicides

“…To the best of our knowledge, this is the first report on the emergence of weeds with multiple resistance to these herbicides in orchards in Asia, including Japan. In previous studies, resistance to both glyphosate and glufosinate due to repeated use of these herbicides has been reported in Eleusine indica in a vegetable farm and oil palm nursery in Malaysia (Jalaludin et al 2015), L. multiflorum and L. perenne in vineyards in New Zealand (Ghanizadeh et al 2015), and L. multiflorum in vineyards and pear orchards in California, USA (Karn et al 2018). In the Japanese pear orchards in this study, glyphosate- Field 3 0.00 99.1 ± 0.9 a 1.00 0.9 ± 0.9 b and glufosinate-based herbicides have been repeatedly used every year.…”

“…Resistance to both glyphosate and glufosinate has been confirmed in Eleusine indica (L.) Gaertn. in a vegetable farm and oil palm nursery in Malaysia (Jalaludin et al 2015), L. multiflorum in hazelnut orchards in Oregon, USA (Avila-Garcia & Mallory-Smith 2011), L. multiflorum in vineyards and pear orchards in California, USA (Karn et al 2018), and L. multiflorum and Lolium perenne in vineyards in New Zealand (Ghanizadeh et al 2015). In Japan, resistance to glyphosate (Ichihara et al 2016, Niinomi et al 2013) and glufosinate (Ichihara et al 2018) and multiple resistance to these herbicides (Ichihara et al 2018) have been confirmed in L. multiflorum populations in the levees of rice paddies in Shizuoka Prefecture.…”

Recurrent Selection with Glufosinate at Low Rates Reduces the Susceptibility of a Lolium perenne ssp. multiflorum Population to Glufosinate

“…multiflorum (Italian ryegrass) is one of the major weed species in orchards, vineyards, field crops, and fallow fields of California [10,11]. Extensive herbicide use has exerted strong selection that has resulted in the evolution of herbicide resistance in many populations of this weed species in California [11][12][13][14][15]. Resistance to glyphosate [11,13,16], paraquat, and the ACCase inhibitor, sethoxydim [14], as well as multiple herbicide resistance to these three herbicides plus acetolactate synthase (ALS) inhibitors [14,15] have been confirmed in populations across the agricultural landscape of northern California.…”

“…Glufosinate is an alternative non-selective post-emergence herbicide that can still be used to control herbicide-susceptible and most herbicide-resistant L. perenne ssp. multiflorum in California, as only two populations with glufosinate resistance have been documented to date [13]. Both are populations with low resistance levels (1.6-2 fold) compared to the standard susceptible population.…”

Responses of Lolium spp. to glufosinate ammonium application at different temperatures

“…Evolution of weed resistance to herbicides has become a major problem for agricultural systems and, eventually, global food security (Karn et al, 2018). These authors noted that Lolium perenne L.…”