Analysis of rhizobacterial community associated with the occurrence of Ganoderma basal stem rot disease in oil palm by Illumina next-generation sequencing

Abstract

The fungus Ganoderma boninense is a causal pathogen of basal stem rot, a serious disease of oil palm plantation systems. As previously observed, some oil palm trees show no appearance of disease symptoms (asymptomatic oil palm), although they have grown close to a tree that showed severe symptoms of basal stem rot disease (symptomatic oil palm). The microbial community difference between asymptomatic and symptomatic oil palm will help understand disease suppression. Thus, in this study, rhizosphere soil was sampled around asymptomatic (OP - G) and symptomatic (OP + G) oil palm trees in Ganoderma-infected oil palm orchards. Illumina next-generation sequencing (NGS), bioinformatics analysis, bacterial diversity, and soil physicochemical properties were evaluated. The results demonstrated that soil physicochemical properties and species richness around rhizosphere soil of OP - G and OP + G samples were not significantly different. The age of the oil palm trees and oil palm variety showed negligible correlation and were not significant with bacterial diversity. However, the top ten most abundant analysis of the bacterial communities showed that phyla Actinobacteria and Firmicutes were significantly increased in rhizosphere soil around OP - G samples relative to the OP+ G samples. The unique operational taxonomic units (OTUs) of OP - G (2137) were higher than in the OP+ G samples (1747 OTUs). These bacterial communities have been reported as biological control agents and/or plant growth-promoting rhizosphere bacteria that are related to disease suppression. Thus, the data provided are useful for developing suppressive soil to biologically control G. boninense.

Keywords: Disease suppression; Ganoderma basal stem rot; Illumina next-generation sequencing; Oil palm; Rhizobacterial community.