Screening of Endophytic Fungal Isolates Against Raffaelea quercus-mongolicae Causing Oak Wilt Disease in Korea

Abstract

Oak wilt disease caused by Raffaelea quercus-mongolicae has emerged obviously in Korea. We selected antifungal isolates against R. quercus-mongolicae among 368 endophytic fungal isolates from different parts of oak and pine trees. The experiment was conducted in the primary and secondary screenings by dual culture test. The antifungal activity of the selected isolates was assessed in culture filtrate test based on the inhibition rates in mycelial growth, sporulation, and spore germination of oak wilt fungus. Five isolates, E089, E199, E282, E409 and E415, showed strong antifungal activity in culture filtrate test, and their antifungal activity decreased on the culture media supplemented with heated culture filtrate. Higher mycelial growth inhibitions on the unheated media were recorded in E409 (Colletotrichum acutatum), E089 (Daldinia childiae), E415 (Alternaria alternata) and E199 (Daldinia childiae) with the inhibition rates of 79.0%, 70.1%, 68.9% and 64.5%, respectively. These isolates also had the higher sporulation inhibitions on unheated media with the rates of 96.8%, 84.2%, 82.8% and 80.5%, respectively. The spore germination of the oak wilt fungus was completely inhibited by E282 (Nectria balsamea) on both unheated and heated media. These results showed that a higher number of potent antifungal isolates against oak wilt fungus was isolated from the petiole compared to the other parts. This study could contribute to the development of biological control approaches for the management of oak wilt disease caused by R. quercus-mongolicae.

Effect of Isolation Conditions on Diversity of Endolichenic Fungal Communities from a Foliose Lichen, Parmotrema tinctorum

“…The most abundant species, Daldinia childiae complex, was isolated from all individual lichen samples and under all isolation conditions. D. childiae was recovered both from the branch of pine trees and lichen thalli [ 42 , 43 ]. D. childiae has been reported to be a putative saprobe that stays in fresh host-plant tissue without causing the disease symptoms for a long time [ 44 ].…”

A chromosome‐scale genome assembly of the Mongolian oak (Quercus mongolica)

“…According to the International Union for Conservation of Nature Red List of Threatened Species v3.1 (https:// www.iucnr edlist.org/), this economically and ecologically valuable oak species is threatened by illegal timber trade and harvesting, and its populations is continuously declining (Barstow, 2018). Previous studies of Q. mongolica have focused on its genetic diversity (Chen et al, 2021;Pang et al, 2019), evolutionary history (Liao et al, 2019;Zeng et al, 2011Zeng et al, , 2015, and disease (Kim et al, 2016;Nguyen et al, 2020;Watanabe et al, 2014). However, to date, no nuclear genome resources are available for Q. mongolica, although a chloroplast genome has been reported (Xia & Wang, 2019).…”

Antifungal Activity and Effect of Plant-Associated Bacteria on Phenolic Synthesis of Quercus robur L.

“…[ 34 ]. Inoculation of Pseudomonas denitrificans bacteria into oak seedlings grown in containers after subsequent infection of the plants with oak wilt ( Raffaelea quercus-mongolicae ) reduced the number of diseased plants by half [ 18 , 79 , 81 , 82 ]. Therefore, the ability of endophytic bacteria to biocontrol the growth and spread of phytopathogens reveals the prospects of their use as biopesticides.…”

“…Nowadays, special attention has been paid to studies of taxonomic groups of endophytes, potential ways of colonization of plant tissues and organs [ 12 , 13 ], physiological processes responsible for the formation of the acquired resistance of plants [ 14 , 15 , 16 ], and plant-microbial interactions and expression of related genes [ 17 , 18 , 19 , 20 ]. Some species of endophytic bacteria are capable of fixing atmospheric nitrogen [ 21 , 22 , 23 , 24 ].…”