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Effect of Sampling Time, Quantification Method, and Tree Sample Pooling on Phytophthora cinnamomi Root Quantities in
Jenna B Jolliffe1, Elizabeth K Dann2, Marieta van der Rijst3
1Department of Plant Pathology, Stellenbosch University, Stellenbosch 7600, South Africa.
Plant Disease
|October 8, 2023
Summary
Accurate quantification of Phytophthora cinnamomi in avocado roots is possible using either qPCR or baiting methods, with specific pooling strategies suitable for disease management. Sampling time impacts pathogen levels, with higher levels observed in late autumn in some orchards.
Area of Science:
- Plant Pathology
- Agricultural Science
- Mycology
Background:
- Phytophthora cinnamomi causes devastating root rot in avocado worldwide.
- Understanding pathogen quantification in avocado roots is crucial for effective disease management.
Purpose of the Study:
- To investigate the impact of root sampling time, quantification method (qPCR vs. baiting), and tree pooling strategies on Phytophthora cinnamomi quantification in avocado roots.
- To identify optimal methods for pathogen detection and inform disease management timing.
Main Methods:
- Field study across six avocado orchards in South Africa over two years.
- Comparison of two tree sample pooling strategies (four-pooled and single-pooled groups).
- Quantification of Phytophthora cinnamomi using quantitative real-time PCR (qPCR) and root baiting.
Main Results:
- Both four-pooled and single-pooled strategies were suitable for quantifying Phytophthora cinnamomi.
- qPCR was more sensitive than baiting in detecting differences in pathogen levels over time.
- Pathogen root quantities in 2018 were higher in May (late autumn) compared to other sampling times.
- Pathogen DNA levels correlated positively with soil temperatures of 20-29°C and negatively with 15-19°C two months prior to sampling.
Conclusions:
- Established suitable tree sample pooling strategies and quantification methods for Phytophthora cinnamomi in avocado roots.
- Demonstrated the influence of sampling time and soil temperature on pathogen levels.
- Findings provide a basis for understanding pathogen biology and implementing timely disease management strategies.
