Quantifying the Emergence Response of Various Ecotypes of littleseed Canarygrass (Phalaris minor Retz.) to Temperature

Document Type : Research Article

Authors

Ghodsiyeh Arezoogar

Afshin Soltani

Asieh Siahmarguee

Farshid Ghaderi-Far

Department of Agronomy, Faculty of Crop Production, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran

10.22067/jpp.2026.95779.1255

Abstract

Introduction
Phalaris minor Retz., commonly known as little seed canary grass, is one of the most troublesome and competitive weeds in wheat fields. Due to morphological similarities and growth requirements with wheat, the yield reduction of this crop is reported to be between 28 and 95 percent. Furthermore, the resistance of P. minor to herbicides that inhibit PSII, ACCase, and ALS has been documented in Iran as well as in other nations, with research results suggesting that this issue is proliferating swiftly. Therefore, understanding the biology and emergence patterns of P. minor is crucial for designing effective integrated weed management strategies. The use of predictive models of seedling emergence is essential for successful management and for reducing the population of resistant biotypes. These models allow farmers and agronomists to anticipate periods of high weed emergence and optimize the timing of cultural, mechanical, and chemical control practices. A precise understanding of plant developmental responses to temperature is a prerequisite for developing accurate models to estimate emergence timing under variable environmental conditions. Despite its significance, data concerning the cardinal temperatures for seedling emergence of various Phalaris ecotypes (Phalaris spp.) remains insufficient, thereby restricting the effective application of predictive models under field conditions.
 
Materials and Methods
This study was conducted to investigate and quantify the response of four Phalaris ecotypes (Gorgan, Kordkuy, Ziarat, and Kalaleh) to temperature, and to estimate their cardinal temperatures using appropriate mathematical functions. The experiment was carried out across 12 sowing dates (from December 2023 to November 2024, one sowing date per month) in a randomized complete block design (RCBD) with three replications under non-limiting water and nutrient conditions at the Agricultural Sciences and Natural Resources University of Gorgan. Prior to the experiment, all weeds from the experimental site and its surroundings were completely removed to minimize competition. The soil was then manually tilled with a shovel (surface tillage) and mixed with farmyard manure to provide a soft and suitable seedbed that facilitates uniform seed-soil contact. Before each sowing date, seeds were subjected to appropriate dormancy-breaking treatments to ensure maximum germination potential and were immediately transferred to the field for sowing. Different sowing dates were selected to expose the plants to varying temperature conditions and to examine the effect of temperature on seedling emergence. Emergence was recorded according to the Zadoks scale when the coleoptile or any part of the seedling was visible on the soil surface in 50% of the viable seeds sown. Observations were conducted every other day and daily during the warmer months to accurately capture emergence dynamics under fluctuating environmental conditions. Data analysis was performed using SAS statistical software, while the plotting and analysis of data-related graphs were performed using Microsoft Excel to visualize trends and model fits.
 
Results and Discussion
Among the models used, the two-segmented and three-segmented models showed similar performance based on statistical indices, with RMSE values of 1.60 and RRMSE values of 14.2%, respectively. The beta model, with an RMSE of 1.94 and an RRMSE of 16.8%, exhibited weaker performance compared with the other two models. However, model fitting results showed that the beta model failed to estimate the base temperature, yielding an unrealistic value of approximately -20 °C. Consequently, in the next step, a constraint was imposed on the base temperature (a range between 0 and 5 °C was selected for the base temperature; however, this constraint also had no effect on model performance and failed to estimate the base temperature and its standard error). Additionally, the three-segmented model was also unable to provide a valid standard error (SE) estimate for the ceiling temperature. As a result, both models were unsuccessful and unsuitable for integrated estimation of cardinal temperatures, and only the two-segmented model proved effective in this regard. Therefore, the two-segmented model was selected as the superior model, and the cardinal temperatures derived from this model should be adopted. The two-segmented model indicated that the base, optimum, and ceiling temperatures were 3.8, 21.8, and 30.2 °C, respectively. The duration required for seedling emergence (expressed as biological days: the number of days to emergence at the optimum temperature) was estimated to be 5.34 days. Statistical analysis showed that, within the framework of the superior model, no significant differences existed among the ecotypes regarding the cardinal temperatures or the biological days required for emergence. Our result showed that high temperature (above 30 °C) could be associated with the absence of emergence on certain sowing dates (from May to August 2024).
 
Conclusion
The findings showed that different ecotypes of Phalaris in Golestan province exhibited a similar response to temperature, indicating ecological stability and high adaptability of Phalaris under diverse environmental conditions. Therefore, their management can be carried out using common strategies. Also, further studies are needed to quantify the temperatures that may induce dormancy.

Keywords

Biological day

Cardinal temperatures

Modeling

Subjects

• Weed

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Authors retain the copyright. This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)

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