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A pattern recognition tool for quantitative analysis of in planta hyphal growth of powdery mildew fungi
1Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, D-06466 Gatersleben, Germany.
Abstract:
The development of fungal pathogens can be quantified easily at the level of spore germination or penetration. However, the exact quantification of hyphal growth rates after initial, successful host invasion is much more difficult. Here, we report on the development of a new pattern recognition software (HyphArea) for automated quantitative analysis of hyphal growth rates of powdery mildew fungi on plant surfaces that usually represent highly irregular and noisy image backgrounds. By using HyphArea, we measured growth rates of colonies of the barley powdery mildew, Blumeria graminis f. sp. hordei, on susceptible and induced-resistant host plants. Hyphal growth was not influenced by the resistance state of the plants up to 48 h postinoculation. At later time points, growth rate increased on susceptible plants, whereas it remained restricted on induced-resistant plants. This difference in hyphal growth rate was accompanied by lack of secondary haustoria formation on induced-resistant plants, suggesting that induced resistance in barley against Blumeria graminis is caused mainly by reduced penetration rates of primary as well as secondary appressoria leading, finally, to fewer and less-developed fungal colonies. No evidence was found for reduced nutrient-uptake efficiency of the primary haustoria in induced-resistant leaves, which would be expected to have resulted in reduced hyphal growth rates during the first 48 h of the interaction.
Insights
A new software, HyphArea, quantifies fungal hyphal growth. Powdery mildew growth on barley was initially unaffected by resistance but later slowed on resistant plants, indicating reduced penetration is key to resistance.
Area of Science:
- Plant pathology
- Mycology
- Computational biology
Background:
- Quantifying fungal pathogen development post-invasion, specifically hyphal growth rates, is challenging.
- Traditional methods struggle with irregular and noisy plant surface image backgrounds.
Purpose of the Study:
- To develop and validate a novel pattern recognition software, HyphArea, for automated quantitative analysis of fungal hyphal growth.
- To investigate the hyphal growth dynamics of barley powdery mildew (Blumeria graminis f. sp. hordei) on susceptible and induced-resistant barley plants.
Main Methods:
- Development of HyphArea software for automated image analysis of fungal hyphae.
- Measurement of Blumeria graminis f. sp. hordei colony growth rates on susceptible and induced-resistant barley.
- Assessment of haustoria formation and correlation with hyphal growth.
Main Results:
- Hyphal growth rates were not significantly different between susceptible and resistant plants within the first 48 hours post-inoculation.
- Later time points (beyond 48h) showed increased hyphal growth on susceptible plants, while growth remained restricted on induced-resistant plants.
- Reduced secondary haustoria formation was observed on induced-resistant plants, correlating with restricted fungal growth.
Conclusions:
- Induced resistance in barley against Blumeria graminis is primarily mediated by reduced penetration rates of both primary and secondary appressoria.
- The software HyphArea provides a reliable method for quantifying hyphal growth in challenging plant-pathogen interactions.
- Nutrient uptake by primary haustoria does not appear to be the limiting factor for hyphal growth during the initial 48 hours of interaction in this system.
