Molecular diagnosis of the brown root rot disease agent Phellinus noxius on trees and in soil by rDNA ITS analysis

Abstract

Phellinus noxius (P. noxius) is an important pathogen that causes brown root rot of trees in tropical and sub-tropical areas and has led to severe damage to trees. A quick and accurate diagnostic technique is essential to the timely confirmation of the pathogen and possible treatment. In this study, a fast, sensitive and accurate approach of molecular technique was used to diagnose the brown root rot pathogen on trees and in soils of subtropical Hong Kong. Two pairs of specific PCR primers were used to amplify the target rDNA internal transcribed spacer (ITS) region through polymerase chain reaction (PCR) for both tree tissues and soil samples. The amplified ITS fragments were then sequenced and analyzed phylogenetically for the diagnostic identification of the pathogen P. noxius. The results showed that 13 of 38 suspected trees in Hong Kong were infected with P. noxius through molecular detection. The pathogen showed no specific preference to any particular tree species. Quantitative PCR was applied to soils grown with trees identified both positive and negative for P. noxius, but the soils with healthy trees were also found positive for P. noxius. For the first time, P. noxius was reported to infect a wide range of tree species in Hong Kong and widely presented in soils, probably serving as a reservoir for the pathogen. Through this study, it is proposed that P. noxius is a soil-borne pathogen, which increases its infectivity when trees start to grow in the soil as a means in addition to the previously proposed root-to-root contact.

The brown root rot fungus Phellinus noxius affects microbial communities in different root‐associated niches of Ficus trees

“…gov.tw/fhsnc), BRR accounted for $30% of the reported cases every year, and $30% of the reported BRR cases were observed in F. microcarpa in the last decade. Ficus trees in Hong Kong and Okinawa are also seriously threatened by BRR (Sahashi et al, 2012;Wang et al, 2016). A recent study by Tsang et al (2020) characterized the microbiomes in the rhizosphere soil of P. noxius-infected F. microcarpa, Celtis sinensis, Mallotus paniculatus, and Cinnamomum camphora (Tsang et al, 2020).…”

“…According to the database of Forest Disease Information Centre in Taiwan (https://health.tfri.gov.tw/fhsnc), BRR accounted for ~30% of the reported cases every year, and ~30% of the reported BRR cases were observed in F. microcarpa in the last decade. Ficus trees in Hong Kong and Okinawa are also seriously threatened by BRR (Sahashi et al ., 2012; Wang et al ., 2016). A recent study by Tsang et al .…”

Commodity risk assessment of bonsai plants from China consisting of Pinus parviflora grafted on Pinus thunbergii

“…(a) Pyrrhoderma noxium is present in China with reports from Hainan island (Ann et al, 2002;Wang et al, 2016;, Hebei province (GBIF, online), Macao in Guangxi province (Wang et al, 2016) and Kinmen/ Chinmen island (Watling et al, 2002).…”