Distribution and frequency of resistance to four herbicide modes of action in Lolium rigidum Gaud. accessions randomly collected in winter cereal fields in Spain     

Iñigo Loureiro  Enrique Rodríguez-García  Concepción Escorial  José María García-Baudín  José Luis González-Andújar  María Cristina Chueca 《Crop Protection》2010

Lolium rigidum is the most prevalent and damaging grass weed of winter cereals in Spain. L. rigidum infestations are frequently treated with herbicides and, consequently, populations have evolved resistance. The objective of this study was to determine the extent and frequency of herbicide resistance in L. rigidum populations in Spain to the selective herbicides chlortoluron, diclofop-methyl and chlorsulfuron, commonly used for its control in-crop, and to glyphosate. The response to these herbicides was evaluated on 123 accessions surveyed randomly across cereal cropping areas of the regions of Castile and León, Catalonia and Andalusia. The fresh weight and the frequency of undamaged plants were calculated for each accession and herbicide. At the regional level, higher frequencies of accessions displaying resistance occurred in Catalonia, an intensively cropped region with a greater herbicide selection pressure. Of concern is that in this region the 60% of the accessions displayed some level of resistance to the ALS-inhibiting herbicide chlorsulfuron. The 6.9% of the accessions found in Castile and León with some resistance to glyphosate could also indicate an incipient problem of resistance to this herbicide. For the other herbicides and regions the majority of the accessions remained susceptible. The possible mechanisms of herbicide resistance development in L. rigidum accessions (target-site versus non-target-site resistance) and their variation among regions was discussed. This study can be used to generate herbicide resistance-management schemes for farmers, based upon the herbicide the site and the potential for resistance development.  相似文献   

Possible involvement of herbicide sequestration in the resistance to diclofop-methyl in Italian biotypes of Lolium spp.     

Giovanni Dinelli  Alessandra Bonetti  Ilaria Marotti  Maurizio Minelli  Pietro Catizone 《Pesticide biochemistry and physiology》2005,81(1):1-12

The mechanism of resistance to diclofop-methyl in three Italian populations of Lolium spp. (two resistant and one susceptible) was investigated. The major proportion of R-1 (Tuscania 1997) and R-2 (Roma 1994) plants (approximately 80%) survived after herbicide treatment by emitting new tillers from the crown. Both resistant (R-1 and R-2) and susceptible (Vetralla 1994) Lolium spp. populations were target-site sensitive. No difference in diclofop-methyl absorption by shoots of resistant and susceptible biotypes was observed. At the dose corresponding to 1× the recommended field rate, a relatively higher metabolism was found in R-2 biotype. In contrast, at the doses 2× and 10× the field rate no difference in herbicide metabolism between susceptible and resistant biotypes was observed. At all the three herbicide doses (1×, 2×, and 10× the field rate) 48 h after the treatment (HAT), the total amount of metabolites produced by wheat was more than three times higher than that produced by resistant and susceptible ryegrass biotypes. At the doses 1× and 2× the field rate, the herbicide translocation was different in the susceptible biotypes compared to resistant biotypes. The total amount of the radiolabel found 48 HAT in culm and root was approximately twice in susceptible biotype than in resistant biotypes. Susceptible and resistant ryegrass biotypes differed in the capability of their roots to acidify the external medium. Susceptible biotype acidified the external solution at approximately 6 times the rates of the resistant biotypes. In the present study, the mechanism responsible for resistance in the investigated resistant biotypes was not univocally identified. Indirect evidence supports the possible involvement of herbicide sequestration or immobilization.  相似文献   

Diclofop-methyl dissipation in clay soil under different tillage systems in central Italy     

M. Mazzoncini  R. Lorenzi  R. Risaliti  C. Sorce  M. Ginanni  M. Curadi  R. Pini 《Soil & Tillage Research》1998,46(3-4):241-250

In order to evaluate the effect of simplified tillage systems on herbicide dissipation, diclofop-methyl residues were monitored in different soil layers (0–5 cm, 5–10 cm and 10–30 cm) under three different tillage systems: ploughing 25–30 cm deep (PT), disk harrowing 7–12 cm deep (RT) and no-tillage (NT) in a long-term experiment started in 1990 and carried out on clay soil. Diclofop-methyl residue concentrations in the soil were 0.25 ppm at peak time in topsoil and at lower quantities in the deeper layers. Diclofop-methyl residues in the topsoil were often higher with PT as compared to RT and NT. The presence of diclofop-methyl increased suddenly in untilled plots after a heavy rainfall period. This occurred in the 5–10 cm soil layer 60 days after application, and in the 10–30 cm soil layer 90 days after application. These data suggest a more rapid diclofop-methyl displacement to ground water through macropores under NT conditions.  相似文献