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Sources, Detection, and Inoculum Quantification of Flower Blight Pathogens in Macadamia
Kandeeparoopan Prasannath1, Victor J Galea2, Olufemi A Akinsanmi1
1The University of Queensland, Queensland Alliance for Agriculture & Food Innovation, Centre for Horticultural Science, Dutton Park, QLD 4102, Australia.
Phytopathology
|May 19, 2022
Summary
Flower blight in macadamia, caused by dry, green, and gray molds, leads to significant yield loss. Remnant racemes are a major source of inoculum, necessitating their removal for disease control.
Area of Science:
- Plant Pathology
- Agricultural Science
- Mycology
Background:
- Flower blight, encompassing dry, green, and gray molds caused by *Pestalotiopsis/Neopestalotiopsis*, *Cladosporium*, and *Botrytis* spp., respectively, causes substantial macadamia yield reduction.
- Identifying inoculum sources within the macadamia tree canopy is crucial for managing these devastating diseases.
Purpose of the Study:
- To investigate potential inoculum sources of flower blight pathogens in macadamia trees.
- To quantify the relative abundance of inoculum from different sources.
- To assess the role of remnant racemes and leaf spots in disease transmission.
Main Methods:
- Development and application of a multiplex quantitative PCR (qPCR) assay for pathogen detection and quantification.
- Pathogenicity tests on developing macadamia racemes using conidial suspensions from identified inoculum sources.
- Comparison of disease severity resulting from direct incubation of remnant racemes versus inoculation with conidial suspensions.
Main Results:
- Remnant racemes were identified as a significant source of inoculum for all three flower blight pathogen groups.
- Yellow halo leaf spot primarily contributed *Pestalotiopsis/Neopestalotiopsis* species inoculum.
- Pathogenicity tests confirmed that both remnant racemes and leaf spots can cause severe flower blight symptoms.
Conclusions:
- Preceding season's remnant racemes retained in the tree canopy serve as a crucial overwintering inoculum source for macadamia flower blights.
- Removal of remnant racemes is a viable and recommended control strategy to mitigate flower blight incidence in macadamia orchards.
