Influence of Environmental Factors on the Growth of Colletotrichum godetiae, Causal Agents of Olive Anthracnose in Spain

TL;DR

This study shows that temperature and water availability are the main factors affecting the growth of a fungus that causes olive anthracnose in Spain.

Contribution

The study identifies temperature and water activity as key drivers of Colletotrichum godetiae growth, with no significant impact from elevated CO2.

Findings

Temperature was the main factor affecting fungal growth, explaining 64.2% of the variance in lag time and growth rate.

Water activity and temperature significantly influenced mycelial growth, contributing 38.0% and 34.2% of the variance, respectively.

No growth was observed at 35°C under any water activity or media conditions.

Abstract

Olive anthracnose, the most critical disease affecting fruit and oil quality, is caused by Colletotrichum species, with C. godetiae dominant in Italian and Spanish orchards. Climate change could exacerbate its impact, particularly through rising temperatures and altered CO2 levels. This study evaluated the growth of two C. godetiae strains (Col‐558 and Col‐493) on Potato Dextrose Agar (PDA) and ‘Picudo’ fruit‐agar medium in different assays. Firstly, the strains were incubated at 10°C, 20°C, 25°C and 35°C and CO2 concentrations of 400 and 1000 ppm. Secondly, both strains were grown at the same temperatures but at different water activity (aw) levels (0.90, 0.94 and 0.98). Temperature was the main factor affecting fungal growth, explaining 64.2% of the variance in lag time and growth rate; CO2 had no significant effect. Conversely, aw and temperature significantly influenced mycelial growth, contributing 38.0% and 34.2% of the variance, respectively. An aw of 0.90 consistently resulted in a lag time exceeding 14 days across all temperatures. Furthermore, no growth was observed at 35°C under any aw or media conditions. These findings enhance our understanding of the environmental constraints on C. godetiae growth, highlighting the need for further research to develop mitigation strategies for olive anthracnose.

Growth of Colletotrichum godetiae was mainly driven by temperature and water activity, while elevated CO2 showed no significant effect.

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