Metabolomics differentiation of oil palm (Elaeis guineensis Jacq.) spear leaf with contrasting susceptibility to Ganoderma boninense

Basal stem rot (BSR) disease caused by Ganoderma boninense is the most serious and destructive disease in oil palm, especially in Southeast Asia and required urgent control measures to combat the disease outbreak. Information of understanding metabolite response of oil palm to BSR is limited. Therefore, parental palms with contrasting susceptibility to G. boninense based on previous oil palm progenies testing using root inoculation technique to identify oil palm progenies partially tolerant and susceptible to G. boninense were examined by metabolomics approach using gas chromatography x gas chromatography-time-of-flight mass spectrometry (GC×GC-TOF-MS). Analysis of metabolomics data from GC×GC-TOF-MS was conducted by supervised multivariate analysis of partial least squares-discriminant analysis (PLS) and orthogonal partial least squares-discriminant analysis (OPLS-DA) that allowed cross-validation and response permutation test functions. As a result, seven potential metabolites that contribute to the contrasting susceptibility of oil palms to G. boninense were identified as mannose, xylose, glucopyranose, myo-inositol and hexadecanoic acid which were found high in partially tolerant oil palm whereas cadaverine and turanose were found high in susceptible oil palm as observed in fold changes of detected GC×GC-TOF-MS peaks. The results suggest that the employed strategy is a potential approach to profile and characterize leaf metabolome with contrasting susceptibility to G. boninense. This result provide baseline in future studies utilizing metabolomics in identifying potential biomarkers by screening larger population of truly resistant palms to G. boninense.