A survey of fungi associated with trees in subtropical Hong Kong

Abstract

Fungi associated with trees in urban environment are important in nutrient cycling and disease development of the hosts. The objectives of this study were to investigate the fungal community in rhizosphere soil, the diversity and species assemblage of endophytes, and the diversity, abundance and distribution of wood-decay fungi associated with the Banyan tree, Ficus microcarpa, in subtropical urban environment in Hong Kong, southern China. A total of 324 isolates, obtained from the rhizosphere soil in an incubation experiment, belonged to 25 fungal species based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and morphological characteristics. The fungal community in the soil was dominated by Penicillium spp., Fusarium spp., and Phoma insulana; these fungi have a saprotrophic life style. In addition, Fusicolla acetilerea, Paecilomyces formosus, Dichotomomyces cejpii, and Purpureocillium lilacinum were recorded in Hong Kong for the first time in this study. Another 38 endophytic fungal taxa were established from 154 isolates obtained from six trees at three public grounds. The endophyte community was mainly dominated by Phomopsis species accounting for 22% of the population. Statistical analysis indicated that the distribution of endophytes was related to the location characteristics; endophytes from trees in less disturbed area showed higher similarity than disturbed ones. Endophytes from the south side of the trees at these locations were grouped together; the north side of the trees showed slightly higher species diversity and higher fungal growth than the south side. For wood-decay fungi, 28 species were discovered from 52 samples collected from trees in four parks. Phellinus noxius, Ganoderma gibbosum, and Auricularia polytricha were predominant with both high species abundance and occurrence, and most of them were associated with the old trees. Statistical analysis indicated that the diversity and community structures of wood-decay fungi were related to the age of the parks, the diversity of plant composition and the number of old trees in each park. Moreover, more than 10 species recorded in this study were plant pathogens, causing root-rot, stem-rot, and trunk cavities in trees. Since Trichoderma spp. obtained from the soil, and Pezicula sp. and Sebacinaceae sp. obtained as endophytes are known antagonists towards plant pathogens, they have considerable potential in serving as bio-control agents to inhibit pathogenic wood-decay fungi and promoting the health of the trees. This study presented information of fungal diversity and distribution in subtropical urban environment, and may serve as a basis for further investigations on the pathogenicity, conservation, management and protection of the trees.