Evolution, growth and phenology of Phalaris minor biotypes resistant to ACCase-inhibiting herbicides in Mexico

Abstract

Background: Herbicide application to control weeds can promote a rapid selection of resistant phenotypes in small geographic areas. Also, in areas with a spatial heterogeneous management, resistance may evolve independently, promoting local adaptation in weeds. In the mexican region known as "El Bajio," 100,000 ha are cultivated with wheat, and the weed Phalaris minor, resistant to ACCase-inhibiting herbicides is commonly present. Question:We aim to identify the population structure of two genes in four different P. minor biotypes from "El Bajio" and to determine their association with phenology and plant growth differences (biomass and seed yield) that may contribute to survival in the agricultural environment.Studied species: Phalaris minor Retz. Study site and years of study: The study was carried out at a greenhouse and at the molecular biology laboratory of the Colegio de Postgraduados, during 2013 and 2014. Methods:The diversity of the psbA gene and the sequence of two ACCase gene fragments as well as phenology, growth and biomass allocation were evaluated. Results:Results indicated different polymorphism levels for the two genes. There were no differences in the psbA gene between biotypes, although the ACCase gene exhibited high polymorphism level. In addition, each biotype showed differences in phenology, biomass accumulation and fecundity. Conclusions:The ACCase-inhibiting herbicide resistance in "El Bajio" region might be a resistance hotspot leading to the local adaptation of weeds.Key words: Evolution, herbicide resistance, local adaptation. ResumenAntecedentes: La aplicación de herbicidas para el control de las malezas puede fomentar una rápida selección de fenotipos resistentes en áreas geográficas pequeñas. También, en áreas con un manejo heterogeneo espacial, la resistencia puede evolucionar independientemente, promoviendo adaptaciones locales de las malezas. En la region mexicana conocida como "El Bajío", se cultivan 100,000 ha con trigo, y la maleza Phalaris minor, resistente a herbicidas inhibidores de la ACCasa está comunmente presente.Pregunta: El objetivo fue identificar la estructura poblacional de dos genes en cuatro biotipos diferentes de P. minor de "El Bajío" y determinar su asociación con las diferencias en fenología y crecimiento de la planta (biomasa y rendimiento de semilla) que puedan contribuir a la sobrevivencia en campos agrícolas.Especie estudiada: Phalaris minor Retz. Sitio y años de estudio: El estudio se realizó en un invernadero y en el laboratorio de Biología Molecular del Colegio de Postgraduados durante 2013 y 2014.Métodos: La diversidad del gen psbA y la secuencia de dos fragmentos del gen ACCasa fueron evaluados, así como también la fenología, el crecimiento y la asignación de biomasa.Resultados: Los resultados indicaron diferentes niveles de polimorfismo para los dos genes. No hubieron diferencias en el gen psbA entre los biotipos, aunque el gen ACCasa exhibió nivel alto de polimorfismo. Además, cada biotipo mostró diferencias en la fenología, acumulación de ...

Diversity of Herbicide-Resistance Mechanisms of Avena fatua L. to Acetyl-CoA Carboxylase-Inhibiting Herbicides in the Bajio, Mexico

“…Generalized weed management is not recommended because each farm is a hot spot where the resistant biotypes were selected. Each biotype is locally adapted to its field, and biological traits are synchronized to management practices such as the dates of sowing, physiological maturity, and tillage, among others [9].…”

“…To date, resistant populations of Avena fatua, Phalaris minor, and P. paradoxa have been distributed in the Bajio. The first studies of the resistance mechanism in A. fatua and P. minor concluded that mutations in the site of action caused the resistance [8,9]. Among the main factors contributing to the high prevalence of herbicide resistance in the Bajio is farms' large numbers and area.…”

Herbicide Resistance in Phalaris Species: A Review

“…The net assimilation rate of the biotypes was similar. Additionally, Asp-2078-Gly and Trp-2027-Cys biotypes had a greater leaf area duration due to a higher leaf area, leaf number, and biomass accumulation in leaves [23]. The seed embryo size of the biotypes with the Ile-2041-Asn and Ile-1781-Leu mutations was not statistically different from that of the susceptible biotype, whereas the embryo size was much smaller in the Asp-2078-Gly and Trp-2027-Cys biotypes.…”

“…These substitutions may occur in one position or more than one position in the ACCase gene, which may confer different resistance patterns among the ACCase inhibitors [67]. Amino acid substitutions leading to resistance to ACCase-inhibiting herbicides in different populations of P. minor have also been identified, including amino acids at 1781 [35,40], 2027 [23,40,41,75], 2041 [23,41], and 2078 [45,51]. In these cases, a substitution rendered ACCase insensitive to graminicides in the resistant P. minor population and conferred different resistance patterns.…”

Weed plants used as bioindicators of special soil characteristics

“…In both Guanajuato and Bajio región there is not enough informationon richness and diversity of weed plants, most of literature focuses on control and eradication of these plants in crops, so its is promoted. This practice has resulted in persistence of increasingly resistant and competitives pecies such as Phalaris minor (Poaceae), which is a major problem in wheat crops, 12 and wild oat (Avena fatua), which has generated resistance due to continuous herbicide applications. 10,13 Preliminary observations made by the authors suggests a high endemic weed diversity in the Bajio region, that diversity level might be superior than levels reported in studies carried out in agro ecosystems with less production pressure and consequently less technical and of local-traditional use such as the "milpas".…”