Background and Objectives
Wheat is the most important crop in Iran and every year about 6.5 million ha of arable lands in the country is cultivated by this strategic crop. Weeds cause 23 to 30% reduction in yield of wheat annually. Winter wild oat is the most serious grass weed of wheat fields of Iran. Chemical method is the common way to weed control in wheat fields. ACCase inhibitors such as clodinafop-propargyl, diclofop-methyl and Fenoxaprop-P ethyl + Mefen pair di ethyl are widely used for control of grasses in this regard. Continuous application of herbicides with the same mode of action has resulted in developing herbicide resistant biotypes of weeds such as Avena ludoviciana. The objectives of the current study were: 1) to screen the collected accession of A. ludoviciana suspected to resistance to FOP herbicides, 2) to determine the resistance factor of resistant biotypes and 3) mapping distribution of resistant biotypes.
Materials and Methods
In order to survey Avena ludoviciana resistance to clodinafop-propargy, diclofop-methyl and Fenoxaprop-P ethyl+ Mefen pair di ethyl herbicides in wheat fields of Gonbad-e Kavus, several experiments were conducted in 2014 at Gorgan University of Agricultural Sciences and Natural Resources. (115 populations). The seed bioassay in Petri dish and pot experiment was conducted to determine resistance to acetyl coenzyme Acaboxylase inhibitors (ACCase), respectively. The seed bioassay experiment consisted of screening the suspected populations with discriminating concentration and concentration-response bioassay for resistant populations.
In 48, 27 and 21 populations of A. ludoviciana were resistant to clodinafop-propargyl,
diclofop-methyl and Fenoxaprop-P ethyl + Mefen pair di ethyl herbicides. Resistance accessions indicated varying degrees of resistance to tested herbicides. Based on EC50, the lowest and highest resistance to Clodinafop-propargyl herbicide was shown in Accessions of 74 and 6 with resistance factors of 1.99 and 31.42, respectively. Also for Diclofop- methyl herbicide, EC50 values from 2.88 for accession of 103 (with 1.34 resistanc factor) to 16.02 for accession of 91 (with 7.45 resistance factor) were different. In addition, EC50 estimatedfor Fenoxaprop-P ethyl + Mefen pair di ethyl herbicide was different from 0.124 to 0.86 for 20 and 6 accessions, respectively. Checking the distribution map of resistance accessions showed these accessions had uniform distribution in this city.
Based on these observations, the existence of cross-resistance to herbicides was proved in some of the collected accessions. The results of this study can be used to correct programs designed to manage weeds herbicide resistance and prevent of the development of the plants in other areas.