Introduction
Crown vetch (Coronilla varia) is a perennial tetraploid leguminous plant (2n=24) belonging to the Fabaceae family. Widely used as a decorative ground cover and in erosion control along roadsides, it also plays a vital role in nitrogen fixation, environmental improvement, and soil microclimate enhancement. Native to Central and Southern Europe, its cultivation has expanded to the Mediterranean, Russia, Middle East, and the United States. In Iran, it is found in various provinces such as Mazandaran, Ilam, Lorestan, Guilan, Qom, Kermanshah, Golestan, Kurdistan, and Chaharmahal and Bakhtiari, primarily in pastures, orchards, and field margins. Although primarily valued as forage with nutritional quality comparable to alfalfa, Crown vetch contains toxic compounds like cyanogenic glycosides, notably "croneoline," which pose risks to non-ruminant animals, especially horses. The herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) is used post-emergently for controlling broadleaf weeds in various crops, particularly in no-till systems. Common broadleaf herbicides used in alfalfa fields in Iran include chlorotoluron, paraquat, glyphosate, imazethapyr, topramezone, and bentazone, along with grass herbicides such as fluazifop-p-butyl and haloxyfop-methyl. Atlantis is a herbicide containing methylsulfuron-methyl and iodosulfuron-methyl-sodium from the sulfonylurea active ingredient group; it is widely used for controlling broadleaf weeds as well as some annual weeds in wheat fields. The use of Crown vetch as a cultivated crop in Iran remains limited, and its potential as a weed or a cover crop warrants further investigation.
Materials and Methods
This study was conducted in 2024 at the greenhouse of University of Kurdistan, employing a factorial experimental design based on a completely randomized design with four replicates. The first factor comprised different ecotypes of Crown vetch collected from regions including Nahavand, Hamadan, Semnan, Ilam, Kermanshah, Paveh, Sanandaj, Marivan, Saghez, and Sarvabad. The second factor involved five herbicide treatments: control (no herbicide), tribenuron-methyl (Totrile), tofdordi-b (Tefordib), Granstar ( triflenuron-methyl), and Atlantis (iodosulfuron-methyl sodium + mesosulfuron-methyl + mefenpyr-diethyl). Seeds were prepared by scarification to overcome dormancy, followed by germination in controlled conditions (20°C, 16 hours light, 8 hours dark). Seedlings were transplanted into pots containing a mixture of agricultural soil and sand (1:2). Herbicide treatments were applied via a backpack sprayer 21 days after transplanting, using recommended doses for cereal crops. Data collection included visual damage assessment (0-10 scale), plant height, leaf area index (LAI), and dry weight of aerial parts, measured four weeks post-treatment. LAI was estimated using a logistic growth model based on repeated leaf area measurements. Data analysis was performed using SAS (version 9.4), with ANOVA for mean comparisons via Duncan's multiple range test, and normality verified with Minitab. Graphs and figures were generated in Excel.
Results and Discussion
The study revealed significant effects of herbicides, ecotypes, and their interactions on plant damage, growth, and biomass. Tofordi-b and Totril caused the highest damage (~99% and 95%), indicating strong phytotoxicity, while Atlantis showed minimal impact (~7.5%). Ecotype responses varied, with Marivan being the most resistant (~69% damage) and Sarvabad the most sensitive (~93%). Herbicides significantly reduced plant height, especially Tofordi-b, which decreased height by up to 68%, notably in Saghez. Ecotypes from Paveh and Hamadan showed greater resistance, with less reduction. LAI was markedly affected, with Tofordi-b reducing leaf area by about 59%, and residual LAI was higher in Paveh and Hamadan, indicating partial resistance. Dry biomass was also significantly diminished, with Tofordi-b causing an 83% reduction; Paveh maintained higher biomass, reflecting resistance traits. These results suggest that herbicide efficacy varies among ecotypes, influenced by genetic and physiological differences. Highly effective herbicides like Tofordi-b and Totril are promising for weed control, but resistant ecotypes highlight the need for integrated management strategies. The findings underscore the importance of considering ecotype variability to optimize herbicide use and prevent resistance development.
Conclusion
Herbicides like tofdordi-b and Totril show promise in controlling Coronilla varia ecotypes, especially when used as pre-emergence or early post-emergence treatments. Ecotypes such as Paveh and Hamadan exhibit resistance traits that could compromise control efforts if not managed properly. For agricultural applications, especially if Coronilla varia is cultivated as a forage or cover crop, careful selection of herbicide type and timing is essential to minimize crop damage and resistance development. The resistant ecotypes identified could serve as genetic resources for breeding programs aimed at developing resistant cultivars. Further research should focus on molecular mechanisms underlying resistance and the long-term effects of herbicide use on ecotype populations. |
