Different Infection Structures and Point Mutation of <i>Diaporthe citri</i> Showing Resistant against Systemic Fungicides

Soe, Zar Zar; Shin, Yong Ho; Jeun, Yong Chull

doi:2024.40.6.603

Plant Pathol J > Volume 40(6); 2024 > Article

Research Article

The Plant Pathology Journal 2024;40(6):603-614.
DOI: https://doi.org/10.5423/PPJ.OA.07.2024.0112 Published online December 1, 2024.

Different Infection Structures and Point Mutation of Diaporthe citri Showing Resistant against Systemic Fungicides

Zar Zar Soe¹, Yong Ho Shin¹, Yong Chull Jeun^1,2

¹Sustainable Agriculture Research Institute, Jeju National University, Jeju 63243, Korea
²The Research Institute for Subtropical Agriculture and Biotechnology, Jeju National University, Jeju 63604, Korea

Correspondence: Yong Chull Jeun, Tel: +82-64-754-3319, Fax: +82-64-725-2351,
Email: ycjeun@jejunu.ac.kr

Received: 24 July 2024 • Revised: 26 August 2024 • Accepted: 11 October 2024

Abstract

Infection behaviors of some susceptible and resistant Diaporthe citri isolates against two fungicides such as benomyl and kresoxim-methyl were observed on citrus leaves. On the chemically unsprayed leaves, there were no differences in not only the conidial germination rate but also hyphal growth between the resistant and susceptible isolates. However, on the benomyl or kresoximmethyl-pretreated leaves, both conidial germination rate and hyphal growth of the resistant isolates were not decreased, which was different with those of the susceptible isolates. These unchanging germination rate and hyphal growth of the resistant isolates, resulting in the lack of chemical efficacy, coincided with the previous studies in which strong infection was observed by the resistant isolates after pre-treatment with each chemical. On the other hand, a point mutation occurred at 198th amino acid of β-tubulin gene in the resistant isolate NEL21-2 which may cause the resistant against benomyl. However, no mutation was found in cytochrome b in the resistant isolates indicating other genomic changes may be responsible for the resistant against kresoxim-methyl.

Key Words: crop protection, fungicide resistant, infection structure