No abstract

No abstract

Background The development of basal stem rot (BSR) disease in oil palm is associated with lignin during vegetative growth and salicylic acid (SA) biosynthesis. The increase in the lignin content, SA accumulation, growth, and root biomass could indicate the resistance of oil palm seedlings to BSR disease. Therefore, although there are many studies on the interactions between the Ganoderma boninense and oil palm, research on evaluation of physiological processes, biochemistry, and molecules occurring during early internal symptoms of BSR in roots of oil palm (Elaeis guineensis Jacq.) are essential. Results Ganoderma boninense inoculation indicated that C01, C02, and C05 seedlings were susceptible, while the other three seedlings, C03, C07, and C08, were resistant based on Ganoderma Disease Index (GDI). Infection by G. boninense in the most susceptible seedlings C05 reduced fresh weight of roots (FW) by 9.0%, and lignin content by 10.9%. The most resistant seedlings C08 were reduced by only 8.4%, and 0.2% regarding their fresh weight and lignin content, respectively. BSR disease induced SA accumulation in the most susceptible C08 and decreased peroxidase (PRX) enzyme (EC 1.11.1.7) activities in root tissues of oil palm seedlings except C07 and C08 where PRX activities remained high in the 4 months after planting. Infection with G. boninense also increased glutathione S-transferase U19-like (EgGSTU19) gene expression in the root tissues of susceptible seedlings, while laccase-24 (EgLCC24) gene expression was associated with resistance against BSR disease. Based on the relative expression of twelve genes, two genes are categorized as receptors (EgWAKL5, EgMIK1), two genes as biosynthesis signal transduction compound (EgOPR5, EgACO1), five genes as defense responses (EgROMT, EgSOT12, EgLCC24, EgGLT3, EgGSTU19), and one gene as trans-resveratrol di-O-methyltransferase-like (EgRNaseIII) predicted related to BSR infection. While two other genes remain unknown (EgUnk1, EgUnk2). Conclusions Ganoderma infection-induced SA accumulation and lignification in resistant accessions promote the seedlings root biomass. Oil palm seedlings have a synergistic physical, biochemical, and molecular defense mechanism to the BSR disease. The utilization of nucleotide-based molecular markers using EgLCC24 gene is able to detect resistant oil palm seedlings to G. boninense.

The Ganoderma boninense is the pathogen causing basal stem rot (BSR) disease in oil palm, degrades oil palm root cell walls and modify plant metabolisms. Research groups have studied molecular mechanisms responses to G. boninense infections. A few have indicated the importance of studying specific gene expressions in relation to resistance mechanisms. This study aims to identify differentially expressed genes in oil palm roots showing susceptible or resistance responses and visualize their accumulated transcript in the heatmap form. The susceptible and resistant seedlings showing symptoms of BSR infection and healthy ones were sampled. Sixteen genes associated with G. boninense infection were identified and their expression were analyzed. Total RNAs were extracted from root samples and cDNA synthesized. Quantitative real time PCR were performed using cDNA, and differential gene expressions were evaluated. Two genes showed the highest transcript accumulation in susceptible and resistant seedlings treated with or without G. boninense. Ten out of the 16 genes belonged to Group I and the other six to Group. Seven out of the 16 genes were differentially expressed in the samples either with or without G. boninense inoculation. The seven genes may be associated with early infection responses to G. boninense.