# Etiology of Foliar Blight of Indian Paintbrush (Castilleja tenuiflora) in Mexico

## TL;DR

This study identifies two fungi, Alternaria alternata and Alternaria gossypina, as the cause of leaf blight in the Mexican plant Castilleja tenuiflora, which is used in traditional medicine.

## Contribution

The first report of Alternaria species causing leaf blight in Castilleja tenuiflora and the first record of Alternaria gossypina in Mexico.

## Key findings

- Alternaria alternata and Alternaria gossypina were identified as the pathogens causing leaf blight in C. tenuiflora.
- The disease incidence was 80% with up to 5% leaf area affected.
- This is the first report of these pathogens in C. tenuiflora and A. gossypina in Mexico.

## Abstract

Castilleja tenuiflora is a native perennial plant used in traditional Mexican medicine. In June 2022, leaf blight symptoms were observed in a wild population of C. tenuiflora plants. Disease incidence was 80% and disease intensity reached up to 5% of the leaf area. Currently, there are no reports of pathogens causing leaf blight in this plant; therefore, this work aimed to identify the fungi responsible for the disease. The fungi recovered from the diseased tissue were characterized by means of pathogenicity tests and cultural, morphological, and molecular characterization. The information obtained revealed that Alternaria alternata and Alternaria gossypina are the pathogens responsible for the disease. This is the first report implicating species of Alternaria in causing leaf blight of C. tenuiflora in Mexico, as well as the first report of Alternaria gossypina also in Mexico. These pathogens may threaten the in situ conservation of native C. tenuiflora populations and limit their in vitro propagation. Future research lines should focus on determining the effect of these pathogens on metabolite production.