Fig 1.
Symptoms of vascular wilt in A. sinensis trees and morphological characteristics of F. oxysporum isolated from an infected tree.
(A) Healthy tree branches. (B,C) Infected tree with yellowing, defoliation. (D) Symptoms after infection. A. sinensis stems are dark brown (DB) when infected by pathogens. (E) Fungal colonies formed on PDA after three days. (F) Microconidia (MI) and macroconidia (MA) of a 10-day-old F. oxysporum culture on PDA.
Fig 2.
Phylogenetic analysis of the isolated F. oxysporum with a selection of Fusarium species.
Fig 3.
Histological observation of stems inoculated with F. oxysporum and wild agarwood sample of A. sinensis.
(A) Tangential section of A. sinensis stem inoculated with F. oxysporum 30 days post-inoculation, Bars = 10 mm. (B-D) Light microscope images of the transverse sections of the N (Necrosis), B (Border) and H (Health) zones, respectively, Bars = 50 μm. (E) Wild agarwood sample, Bars = 50 mm. (F) Transverse section of wild agarwood, Bars = 50 μm. IP: interxylary phloem, XR: xylem ray, V: vessel.
Fig 4.
Identification and quantification of F. oxysporum in stems of A. sinensis after one-month inoculation.
(A) Agarose gel electrophoresis of PCR products using the F. oxysporum-specific primers FOF1 and FOR1, Lane 1: DL2000 DNA marker (Takara, Japan), Lane 2: F. oxysporum, Lane 3: negative control. (B) Distribution of the colony forming unit per one gram (CFU/g) of F. oxysporum in the N (Necrosis), B (Border) and H (Health) zones.
Fig 5.
Thin-layer chromatography (TLC) chromatogram of methanol extracts.
TLC chromatogram visualized under UV254 nm (A) and UV365 nm (B). (C) Stained and immobilized TLC chromatogram.
Fig 6.
The contents of alcohol-soluble extractive and essential oils in the brown zone (B), wild agarwood (W), and healthy zone (H).
(A) Alcohol soluble extractive content; (B) essential oil content.
Fig 7.
HPLC chromatograms of five chromones in the brown zone (B), wild agarwood (W), and healthy zone (H).
The standard mixtures of (1) AH1, (2) N, (3) AH3, (4) AH8, and (5) AH6 are shown in (A). The presence of these chromones in H, B, and W are shown in (B-D).
Fig 8.
The contents of five chromones in the brown zone (B), wild agarwood (W), and healthy zone (H).
Fig 9.
GC chromatograms of the three essential oils in the brown zone (B), wild agarwood (W), and healthy zone (H).
Table 1.
Chemical composition and relative amounts of essential oils in the brown zone (B), wild agarwood (W), and healthy zone (H).