Abstract
Glyphosate-resistant biotypes of Eleusine indica (L.) Gaertn. have been detected in Asia, the Americas but not in Europe. The aim of this study was to evaluate resistance levels and possible target site resistance mechanisms of an E. indica biotype (19-1) collected from a plant nursery in Southern Italy where poor glyphosate efficacy was reported. Two dose-response experiments were conducted to evaluate the sensitivity of biotype 19-1 to glyphosate in comparison with two susceptible checks. 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) sequencing was performed to identify possible mutations conferring the resistance. The susceptible biotypes were completely controlled at the glyphosate recommended field dose of 360 g ae ha−1, while 50% of the plants of biotype 19-1 survived at 1440 g ae ha−1. The resistance index of biotype 19-1 ranged between 5.8 and 7.3 for the response variables of fresh weight reduction and plant survival, respectively. All the plants surviving glyphosate application and sampled for DNA analyses had the point mutation P106A. The biotype 19-1 can be confirmed as glyphosate-resistant, representing the first glyphosate-resistant population of E. indica in Europe.
Highlights
Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), hindering plant production of aromatic amino acids and leading to plant death
Glyphosate is the most used herbicide worldwide, mainly due to the rapid diffusion of genetically modified (GM) glyphosate-tolerant crops across millions of hectares in North and South America and Australia [1,2]. It has been extensively used for decades as the main weed control tool in perennial tree crops, plant nurseries, gardens, parks and other non-agricultural areas
Seeds of the putative GR biotype, named 19-1, of E. indica were collected at a plant nursery in Southern Italy (41◦ 100 N, 14◦ 090 E, Caserta province) in autumn 2019 from plants surviving repeated glyphosate applications
Summary
Glyphosate inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), hindering plant production of aromatic amino acids and leading to plant death. Glyphosate is the most used herbicide worldwide, mainly due to the rapid diffusion of genetically modified (GM) glyphosate-tolerant crops across millions of hectares in North and South America and Australia [1,2]. It has been extensively used for decades as the main weed control tool in perennial tree crops, plant nurseries, gardens, parks and other non-agricultural areas. The widespread, often exclusive, use of glyphosate over a prolonged period and across huge cultivated areas is causing a continuous selection pressure on weed communities, inevitably leading to the evolution of weed biotypes resistant to this herbicide [2].
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