بررسي واكنش ارقام گندم آبي (.Triticum aestivum L) به كاربرد علفكش توتال 80%WG (متسولفورون-متيل+سولفوسولفورون) در مناطق مختلف كشور

Investigating the response of Irrigated Wheat Cultivars to Herbicide Total® WG 80% (Metsulfuron-methyl + Sulfosulfuron) in Different Regions of Iran

به منظور بررسي واكنش ارقام گندم به علف‌كش توتال 80% WG (متسولفورون-متيل+سولفوسولفورون) آزمايشي در چهار منطقه مشهد، جلگه‌رخ (تربت حيدريه) ، داراب (فارس) و كرج در قالب طرح پايه بلوك هاي كامل تصادفي به شكل آزمايش‌هاي فاكتوريل با چهار تكرار طي دو سال 1390 و 91 به اجرا درآمد. دو عامل آزمايش شامل رقم (5 رقم رايج هر منطقه)، و زمان كاربرد علف‌كش در مرحله رشدي گندم (13، 16و 31 زادوكس) بودند. نتايج حاكي از اختلاف عملكرد ارقام در هر منطقه صرفنظر از زمان مصرف علف‌كش بود. بالاترين عملكرد گندم در مناطق مشهد و جلگه رخ مربوط به رقم پيشگام؛ در كرج مربوط به ارقام پيشگام، ميهن و پيشتاز و در دارب مربوط به ارقام بهرنگ، چمران و ياواروس بود. مصرف علف‌كش در مرحله 13 زادوكس باعث كاهش وزن خشك ريشه ارقام ميهن (32%)، زارع (40%) و گاسكوژن (29%)، نسبت به شاهد بدون سمپاشي در مشهد شد ولي عملكرد دانه كاهش نيافت. سمپاشي در مرحله 31 زادوكس در كرج باعث كاهش معني‌دار درصد وزن خشك ريشه زارع و اورم (41/5% و 30%) ، وزن خشك اندام‌هاي هوايي (16% و 29%) و عملكرد دانه (39% و 35%) در سال اول گرديد. رقم پيشگام بدون هيچ‌گونه پاسخ منفي نسبت به كاربرد علفكش توتال ارزيابي شد. در دو منطقه جلگه رخ و داراب تاثير سوئي ناشي از مصرف علف‌كش توتال بر هيچ‌يك از صفات اندازه‌گيري شده مشاهده نشد.

Introduction:In order for promising lines to be released and introduced to farmers, they are required not only to be subjected to yield comparison tests but they should also be closely examined and evaluated for their response to various environmental stressors. Moreover, it is necessary to determine the safety margin of the selective herbicides for such candidate lines during the process of improvement (Ramsey et al. 2010). So far, more than 45 irrigated wheat cultivars and 20 herbicide formulations for their selective weed control have been commercially registered in Iran. However, since no sensitivity test is conducted on some of these wheat cultivars, there is no documented information available on their response to the registered herbicides, in particular, the sulfonylurea group of herbicides. Mode of action of sulfonylureas is to inhibit the formation of acetolactate synthase (ALS), which is a key enzyme for the synthesis of amino acids such as lucid, iso ucin and valin (Blair & Martin, 1988). In our experiments, we determined the relative response of 11 commonly grown wheat cultivars in four regions of Iran to the application of herbicide metsulfuron+ sulfosulfuron (Total®), which is the most frequently used herbicide to control wild barley in the regions where wheat is cultivated. Materials and Methods: A field study was conducted in four regions of Iran, including Mashhad, Jolgeh- Rokh (in Torbat-Heidarieh), Darab (in Fars) and Karaj during 2011 and 2012 growing seasons. The experimental layout at all testing locations was completely randomized block design in factorial arrangement of the treatments with four replicates. Treatments were wheat cultivars (five cultivars chosen from 11 recommended cultivars for each region) and three herbicide application timings (at either Z13, Z16 or Z31 according to Zadoks growth stages for wheat). Root and shoot dry weight of plant samples were determined in early growth stages. Grain yield and visual injury assessment were subjected to statistical analysis and means were separated by DMRT (α=5%). Results and Discussion: Results showed significant differences in grain yield of wheat cultivars irrespective of herbicide spraying at different growth stages. The maximum grain yield obtained with Pishgam cultivar in Mashhad and Jolgeh-Rokh, Pishgam, Mihan and Pishtaz cultivars in Karaj and Behrang, Chamran and Yavaroose cultivars in Darab. Herbicide application at Z13 caused a significant reduction in root dry weight of Mihan (32%), Zare (40%) and Gascogene (29%) cultivars in Mashhad but no significant reduction was observed in shoot dry weight and grain yield (expressed in percentage terms relative to their corresponding untreated control). Herbicide application on Orum and Zare cultivars at Z31 decreased dry weight of root (41.5% and 30%) and shoot (16% and 29%) as well as grain yield (39 and 35%), respectively, in the first year of the experiment in Karaj. However, the grain yield did not significantly decline in the second year. Pishgam cultivar did not show any negative response to herbicide application at different growth stages. In Jolgeh-Rokh and Darab, neither visible injury of herbicide on wheat cultivars nor reduction in root and shoot dry weight and/or grain yield were detected. Cold temperatures occurred soon after herbicide application in Karaj and Mashhad. This might be accounted for the increased sensitivity of cultivars to the herbicide although they recovered in most cases. Ferreira et al., (1990) in their study on wheat showed that the injury caused by sulfosulfuron herbicide was more pronounced under colder temperatures. Nevertheless, our results suggest that margin of safety for herbicide application is more dependent on plant phenological stages than the possible coincidence of herbicide spraying and other stress factors, in particular, cold stress. To validate this assumption, it is necessary to conduct complementary experiments that involve applying cold stress as a treatment. 2016Conclusion: Among 11 tested cultivars, most of them displayed no sign of sensitivity to Total® application. Zare was recognized as the most sensitive cultivar, which was followed by Oroum and Gascogene that exhibited relative sensitivity to the herbicide. Keywords: Dry weight, Growth stage, Injury symptom, Sulfonylurea, YieldAcknowledgements: We wish to thank Professor Eskandar Zand, Dr. Masoud Ezatahmadi, Mr. Seyed Hoseein Torabi and Mr. Mohammad Pasban for their useful contribution to this project.