# Pathogenicity and Aggressiveness of Corticioid Basidiomycetes Associated with Stem and Branch Rot of Avocado

## TL;DR

This study identifies corticioid fungi as key pathogens causing white rot in avocado trees, challenging previous assumptions about their role.

## Contribution

The study demonstrates that corticioid basidiomycetes are primary pathogens in avocado white rot, not just secondary saprotrophs.

## Key findings

- Dentocorticium portoricense showed the highest pathogenicity and virulence in avocado white rot.
- Grammothele spp. caused slower, moderate disease progression compared to D. portoricense.
- Phylogenetic analysis confirmed D. portoricense as a distinct pathogen while Grammothele remained unresolved at species level.

## Abstract

Woody tissue diseases of avocado (Persea americana Mill. var. Hass) pose a major phytosanitary threat due to their chronic progression, late symptom expression, and severe impact on tree stability and productivity. Although white rot has traditionally been attributed to saprobic basidiomycetes, increasing evidence suggests corticioid fungi may act as facultative pathogens in agricultural systems. This study examined corticioid basidiomycetes associated with white rot in stems and branches of avocado in Michoacán, Mexico. Field surveys revealed consistent symptoms of structural weakening, branch dieback, and wood decay. Fungal isolates obtained from symptomatic tissues and sporomes were characterized morphologically and identified through ITS-based phylogenetic analyses. Representative isolates of Grammothele spp. and Dentocorticium portoricense were evaluated in pathogenicity assays under controlled conditions. All isolates reproduced field symptoms, confirming pathogenicity, though aggressiveness varied. D. portoricense exhibited the highest incidence, severity, and AUDPC values, indicating greater virulence, while Grammothele isolates showed slower, moderate progression. Phylogenetic analyses provided robust support for D. portoricense, whereas Grammothele was resolved at genus level. Integration of field, pathogenicity, and molecular data demonstrates corticioid fungi are not merely secondary saprotrophs but relevant pathogens in avocado white rot. These findings highlight the need to include corticioid fungi in diagnostic, monitoring, and management strategies for trunk and branch diseases.