Pathogenicity of Rigidoporus microporus and Phellinus noxius against four major plantation tree species in Peninsular Malaysia.

Abstract

Phellinus noxius are destructive fungi in tropical forest plantations. Early stages of infection by these pathogens are often difficult to detect while trees bearing visible disease symptoms are mostly beyond treatment. Little research has been conducted to determine the aggressiveness of these two pathogens on different tree species. This study was conducted on 24-month-old saplings of Acacia mangium, Azadirachta excelsa, Tectona grandis and Hevea brasiliensis. Inoculum blocks of R. microporus and P. noxius were placed next to roots of saplings and left for 30 weeks for infection to take place. The study revealed that R. microporus and P. noxius were pathogenic to all hosts. However, the degree of pathogenicity varied. Phellinus noxius was more pathogenic to H. brasiliensis than to A. excelsa, T. grandis and A. mangium, while R. microporus was more pathogenic to H. brasiliensis and A. excelsa than to A. mangium and T. grandis. In terms of host susceptibility, H. brasiliensis was the most susceptible to R. microporus followed by A. excelsa, T. grandis and A. mangium. Against P. noxius, T. grandis was the most susceptible, followed by H. brasiliensis, A. excelsa and A. mangium. Saplings infected by both pathogens manifested similar aboveground symptoms, but symptoms belowground varied depending on the fungal species. The presence of adhering soil particles and dark brown mycelial crust on the root was common on saplings inoculated with P. noxius, while white rhizomorphs were usually present on the root surface of saplings inoculated with R. microporus.