# First Report of Trametes hirsuta, Causal Agent White Rot in Avocado Trees Grown in the State of Michoacán, México

## TL;DR

This paper reports the first occurrence of Trametes hirsuta causing white rot in avocado trees in Michoacán, Mexico, with significant disease symptoms and a high incidence rate.

## Contribution

The study identifies Trametes hirsuta as a new causal agent of white rot in avocado trees and reports P. americana cv. Hass and Mendez as new hosts.

## Key findings

- Trametes hirsuta was confirmed as the causal agent of white rot in avocado trees in Michoacán.
- The disease incidence reached 60% in sampled orchards with 350 trees per hectare.
- Morphological and molecular tests confirmed the fungus as T. hirsuta.

## Abstract

México is the world’s leading producer of avocado, with 2,540,715 tons in the last year. Trametes spp. are macromycete fungi that rot wood. In 2022, in the state of Michoacán, México, sporomas of Trametes sp. were found in the trunks of avocado trees (Persea americana var. Hass) of 10 years old and older. The trees showed disease symptoms including yellowing of leaves, widespread defoliation, and wilting. It was observed that 10% of the infected trees were felled after heavy rains. In the place where the fungus settled, abundant cream-colored and cottony mycelium developed, causing “white rot”. The incidence of the disease in the sampled orchards was 60% in the tree population per hectare with 350 trees. The symptomatic trees studied were randomly selected from seven orchards. The collected fungal samples show typical structures corresponding to Trametes sp., including large sporomas, a pileus with a surface of concentric zones of various ocher tones, and a porous hymenium. The samples showed a 99% match with the species Trametes hirsuta. Laboratory bioassays of inoculation in fresh wood segments of avocado formed typical sporomas of the pathogen. Finally, the fungus was recovered and reisolated in vitro in PDA, and its identity was confirmed through the morphological characteristics and molecular tests. To the best of our knowledge, this article reports for the first time that P. americana cv. Hass and Mendez are new hosts for T. hirsuta. Therefore, the environmental and horticultural management conditions that favor the proliferation of T. hirsuta must be investigated.