Document Type : Original Article

Authors

• Hossein Hammami ^{1, 2}
• Meisam Mirzaei Nasab ³

¹ Associate Professor, Department of Plant Production and Genetics engineering, Faculty of Agriculture, University of Birjand, Birjand, Iran

² Member of the Plant and Environmental Stresses Research Group, University of Birjand, Birjand, Iran

³ MSc. Student, Department of Plant Production and Genetics engineering, Faculty of Agriculture, University of Birjand, Birjand, Iran

Abstract

Introduction
Drought as abiotic stress and weeds as biotic stress are the major factors that limit crop growth and production in the worldwide, especially in arid and semi-arid regions (Farooq et al., 2012; Abdolahi Norouzi et al., 2024). Drought is also considered the single most devastating environmental stress, which reduces crop growth and productivity more than any other environmental stress (Farooq et al., 2012; Abdolahi Norouzi et al., 2024). The process of dehydration of plants in drought causes fundamental changes in water relations, biochemical and physiological processes, the structure of the membrane cells of the plant. Weeds decrease the growth and productivity of crops by competation for access to radiation, nutrients, and water. Under drought conditions, weeds have a high ability to compete with crops for resources. Moreover, weed management under drought conditions is harder than in normal conditions. Exposer of plant to drought conditions led to morphological, physiological, and biochemical changes in weeds that may affect herbicide performance (Ziska and Dukes, 2011; Alizadeh et al., 2021; Alizadeh et al., 2020; Benedetti et al., 2020). Alizade et al. (2020) concluded that drought restricts photosynthesis and stomatal conductance, reduces absorption, and the effectiveness of the herbicide benzoylpropethyl. Drought increased quinclorac resistance in Echinochloa crusgalli by inducing the metabolic activity of glutathione S-transferases (Wu et al., 2019). Therefore, this experiment was conducted to investigate the performance of clothodim in the control of littleseed canarygrass.
Materials and methods
The experiments of this study were conducted at the research greenhouse of the College of Agricultural, University of Birjand. To obtain maximum seed germination, seeds of littleseed canarygrass were soaked in potassium nitrate solution (2 g.L^{- 1}) under dark conditions at 4 0C for one week. Then the seedlings were sown in 5 L plastic pots. According to Monaco et al. (2002) environmental factors one to two weeks before and after the use of herbicides can affect the absorption of herbicides. Therefore, the plants were grown under field capacity conditions until two weeks after sowing (at the 2-leaf stage). Then, pots were irrigated under three regimes every two days: 100% field capacity, 75% field capacity, and 50% field capacity. The irrigation treatments were conducted two weeks before and after herbicide application. Clethodim at seven levels (zero, 6.25, 12.5, 25, 50, 75, and 100 percent recommended per hectare (120 g.ai. ha^-1)) was applied at four leaf stages. Four weeks after spraying herbicide, the shoots of plants were harvested and immediately weighted. Then, the samples were dried in the oven at 75 °C for 48 hours and reweighted. The roots were washed and separated from the soil by tap water three times. After surface drying, samples were weighted, dried, and reweighted. The experiment data were fitted using the three-parameter logistic equation, and the effective doses of 20, 50, 80, and 90% were calculated. Data analysis was done using SAS 9.4 and R software (drc package). Sigmaplot software was also used to draw the figures.
Results and discussion
The three-parameter logistic regression model provided a reasonable description of the variation in fresh and dry shoots and roots weight for littleseed canarygrass as the applied clethodim doses increased. With increasing clethodim dose, the fresh and dry weight of shoot and root of littleseed canarygrass decreased in three irrigation regimes. However, the decreasing slopes among the irrigation treatments differed. Under 50% field capacity treatments, the effective dose of 90% inhibitor (ED90) on fresh and dry weight of shoots and roots was increased by 86.24%, 17.04%, 85.35%, and 32.51%, respectively. The higher ED90 under 50% field capacity compared to 100% field capacity showed decreased clethodim performance in littleseed canarygrass control. Drought is believed to reduce herbicide efficacy by reducing herbicide absorption, translocation and metabolism in plants. Increasing cuticle layer thickness and reducing the transfer rate of vascular sap, limit the absorption and translocation of herbicides in water-stressed plants (Ziska and Dukes, 2011; Alizadeh et al., 2021; Alizadeh et al., 2020; Benedetti et al., 2020). The degree of adverse effect of water stress on herbicide performance depends on the type of herbicide and weed population (Alizade et al., 2021).
Conclusion
In general, the results of this experiment showed that the application of clethodim under drought conditions, led to decrease clethodim performance on littleseed canarygrass control. By severity of drought stress, performance decreases were higher than control (non stress treatment). The results of this experiment suggested adjusting the herbicide application with the irrigation time to maximize the effectiveness of the herbicide and decrease its consumption. However, further studies are needed in field conditions to prove these results and adjust herbicide doses in drought affected areas.

Keywords

• Active ingredient
• Concentration
• Water-deficit
• Weed

Main Subjects

• Drought stress