Disease prevalence and molecular characterisation of Rigidoporus microporus associated with white root rot disease of rubber tree (Hevea brasiliensis) in Malaysia

Abstract

White root rot (WRR) disease caused by Rigidoporus microporus is a major disease affecting tropical rubber tree (Hevea brasiliensis) and some agricultural crops throughout the world. In Malaysia, rubber industry is an important revenue as natural rubber for export and domestic consumption. The objectives of this study were to determine WRR disease prevalence and characterise R. microporus isolates collected from different regions in Malaysia using cultural and molecular characteristics. During July 2017 to May 2018, diseased samples showing WRR symptoms such as presence of basidiocarps and rhizomorphs in five states of Malaysia including Kedah (Baling), Kelantan (FELCRA Machang and Smallholder in Machang), Perak (Ipoh) and Selangor (Sungai Buloh and UPM Serdang), Sarawak (Bintulu) were obtained. In the field observation, all sampling areas were infected by the root rot disease. Findings revealed that field disease incidence was in the range of 5–40% based on random sampling. The collected R. microporus isolates were pure white and displayed fluffy mycelial growth when cultured on malt extract agar (MEA) medium. For molecular identification, BLASTn analysis showed 98–100% identical to existing reference sequences in the GenBank database. All 27 isolates of R. microporus were characterised based on internal transcribed spacer (ITS) and Beta-tubulin (β-tubulin) gene sequences data. Phylogenetic tree analyses of R. microporus isolates formed two major clades, i.e. Asian and African clades. There was also no clear geographical origin structuring observed within the Asian clade. However, phylogenetic analysis of Beta-tubulin (β-tubulin) gene region revealed distinct geographical origin amongst 27 local isolates. The outcomes of this study provide useful information to improve the existing disease control strategy, hence improving the rubber production in Malaysia.