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QUIK STATS (last updated Jun 27, 2011 )
NOTES ABOUT THIS BIOTYPE
Resistencia de Echinochloa colona (L.) Link al herbicida cyhalofop-butilo en arrozales de Venezuela
Aída Ortiz, Alfredis López
La paja americana [ Echinochloa colona (L.) Link] es una de las malezas de la familia Poaceae de mayorimportancia económica en Venezuela. El objetivo de este trabajo fue determinar la resistencia de 48 accesiones deE. colona a cyhalofop-butilo (inhibidor de la enzima acetil coenzima A carboxilasa, ACCasa). Se establecierondos experimentos, un bioensayo de detección y otro de respuesta a dosis; en el primero se evaluaron accesionesprovenientes de arrozales de los estados productores de Venezuela (Portuguesa, Guárico y Cojedes) y de otras zonassin este cultivo (Aragua y Carabobo), con la dosis recomendada de cyhalofop-butilo (234 g/ha), comparado conun testigo susceptible (‘EC114A’). Se estimó el porcentaje de peso fresco a los 21 días después de la aplicación.Para cuantificar la resistencia , se utilizaron las accesiones ‘EC33P’resistente y ‘EC114A’ como testigo susceptible.Dos accesiones de Portuguesa y cinco de Guárico resultaron resistentes a cyahalofop-butilo (14,58%). La accesión‘EC33P’ mostró un índice de resistencia de 20,78, demostrando la resistencia de E. colona al herbicida cyhalofopbutilo
CONTRIBUTING WEED SCIENTISTS
This study confirms and characterises glyphosate resistance in two polyploid Echinochloa colona populations from north-eastern Australia.
Glyphosate dose response revealed that the two resistant populations were marginally (up to 2-fold) resistant to glyphosate. Resistant plants did not differ in non-target-site foliar uptake and translocation of 14C-glyphosate but contained the known target-site EPSPS mutation Pro-106-Thr and/or Pro-106-Leu. Although plants carrying either a single or two EPSPS mutations were glyphosate-resistant relative to the susceptible population, they were still controlled at the field rate of glyphosate (450 g a.e. ha−1) when treated under warm conditions (25/20 °C). However, when treated in hot conditions (35/30 °C), most mutant resistant plants (68%) can survive the field rate, and an increase (2.5 fold) in glyphosate LD50 was found for both the R and S populations.
This study shows that one or two EPSPS Pro-106 mutations are insufficient in conferring field-rate glyphosate resistance in polyploidy E. colona at mild temperatures. However, control of these mutant plants at the glyphosate field rate is poor at high temperatures, likely due to reduced glyphosate efficacy. Therefore, glyphosate should be applied during relatively mild (warm) temperature periods in the summer growing season to improve E. colona control.
BACKGROUND: Echinochloa colona is an annual weed affecting field crops and orchards in California. An E. colona population carrying a mutation in the EPSPS gene endowing resistance to glyphosate, the most widely used non-selective herbicide, was recently identified in the Northern Sacramento Valley of California. Plants from this population, from a suspected glyphosate-resistant (GR) population, and from one susceptible (S) population collected in the Northern Sacramento Valley of California, were used to generate three GR and one S selfed lines to study possible mechanisms involved in glyphosate resistance. RESULTS: Based on the amount of glyphosate required to kill50%of the plants (LD50), GR lines were 4–9-fold more resistant than S plants and accumulated less shikimate after glyphosate treatment. GR and S lines did not differ in glyphosate absorption, translocation or metabolism. A different target-site mutation was found in each of two of the GR lines corresponding to Pro106Thr and Pro106 Ser substitutions; the mutations were found in different homoeologous EPSPS genes. No mutation was found in the third GR line, which exhibited 1.4-fold higher basal EPSPS activity and a fivefold greater LD50 than S plants. Quantitative RT-PCR revealed that GR lines had similar or lower EPSPS expression than S plants.
CONCLUSION: It is demonstrated that individuals with different glyphosate resistance mechanisms can coexist in the same population, individuals from different populations may carry different resistance mechanisms and different mechanisms can act in concert within single E. colona plants. However, other plant factors or resistance mechanisms appear to modulate plant expression of EPSPS sensitivity to glyphosate.