O. Shevchuk, O. Afanasieva, S. Kryvosheiev, D. Zlenko, I. Hryhorenko

Effect of temperature on Sclerotinia sclerotiorum (Lib.) de bary growth in vitro

Introduction

Effect of temperature on sclerotinia sclerotiorum (lib.) de bary growth in vitro. Find optimal temperature for Sclerotinia sclerotiorum (white mold) growth & sclerotia in vitro. Pathogen develops 5-25°C, with 20°C ideal for mycelial growth & sclerotia formation. Key for research.

Abstract

Goal of this study was to determine the optimal temperature for mycelial growth and sclerotia formation of Sclerotinia sclerotiorum, the causal agent of white mold, under laboratory conditions when cultivated on potato dextrose agar (PDA). Methods. The research was conducted using laboratory, analytical, and statistical methods. The isolate used in the study was obtained from a sunflower head affected by white mold. Mycelial growth and sclerotia formation were studied across a temperature range of 5 to 30°C. Results. It was established that the pathogen develops within the temperature range of 5—25°C, at 30°C no mycelial growth was observed. The most intensive colony growth occurred at 25°C, whereas the highest number of sclerotia formed at 20°C. The greatest sclerotial mass was recorded at 15°C. Significant differences in colony growth rate and sclerotia formation were found depending on the incubation temperature. The highest radial growth rate was observed at 20—25°C, while the lowest was at 5°C. A clear inverse relationship between temperature and sclerotia development time was observed: as the temperature decreased, growth rate slowed and sclerotia formation was delayed. Cultivation at 20°C resulted in the highest number of sclerotia, while both higher and lower temperatures reduced their quantity. In contrast, sclerotial mass was highest at 15°C, with both increased and decreased temperatures resulting in smaller sclerotia. The effect of prior low-temperature cultivation (at 5°C) on subsequent growth was also studied. The results showed that brief exposure to low temperatures did not lead to significant changes in colony growth or sclerotia formation. Conclusion. Sclerotinia sclerotiorum is capable of developing within a temperature range of 5—25°C. The optimal temperature for cultivation on potato dextrose agar in vitro is 20°C, which ensures both intensive mycelial growth and the highest number of sclerotia. These findings can be used to improve protocols for producing infection material for artificial inoculation in phytopathological studies and for studying the pathogen’s biology in the context of climate change.

Review

This study clearly and concisely addresses a critical aspect of *Sclerotinia sclerotiorum* biology: the effect of temperature on its *in vitro* growth and sclerotia formation. The authors successfully delineate the pathogen's developmental range (5-25°C) and identify distinct temperature optima for different growth parameters. Key findings include the most intensive colony growth at 25°C, the highest number of sclerotia at 20°C, and the greatest sclerotial mass at 15°C. The observed inverse relationship between temperature and sclerotia development time, and the lack of significant impact from brief low-temperature exposure, provide valuable insights into the pathogen's adaptability. The conclusion that 20°C represents an optimal balance for overall cultivation (intensive mycelial growth and highest sclerotia number) is well-supported by the presented results, despite the nuanced differences in peak performance for individual parameters. The strengths of this research lie in its focused approach, the systematic testing across a comprehensive temperature range, and the measurement of multiple relevant growth parameters (radial growth, sclerotia number, sclerotia mass). This multi-faceted assessment provides a more complete picture of the pathogen's response to temperature compared to studies focusing solely on mycelial growth. The use of a single isolate from a sunflower head ensures consistency, and the mention of statistical methods indicates appropriate data analysis, which is crucial for establishing significant differences. The study's in vitro nature, utilizing standard PDA medium, allows for controlled experimental conditions, isolating the variable of interest effectively. The findings from this study are highly significant for both fundamental understanding of *S. sclerotiorum* biology and practical applications in phytopathology. The identification of optimal temperatures for different aspects of growth will directly inform and improve protocols for producing infection material for artificial inoculation in controlled experiments, which is essential for screening resistant cultivars or evaluating fungicides. Furthermore, these data contribute meaningfully to understanding the pathogen's epidemiology in the context of changing climatic conditions, allowing for better prediction of disease outbreaks and development of more effective management strategies. Future work could build upon these findings by investigating a broader range of isolates, exploring the interplay with other environmental factors, or validating these *in vitro* results with *in planta* studies.

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