Investigating specialized plant metabolites, traditionally referred to as ‘secondary metabolites’ present in leaf extracts of cashew trees (Anacardium occidentale) resistant and susceptible to anthracnose disease was carried out using metabolomics combined with chemometric tools. We used clones of dwarf-cashew with the following variations of characteristics: resistant and healthy (CCP 76, BRS 226, BRS 189), susceptible and healthy (BRS 265), and another clone also susceptible but affected by the disease (BRS 265). The UPLC-QTOF-MSE (ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry) analysis of the leaves of Anacardium clones allowed us to annotate a total of 39 metabolites. The multiple orthogonal partial discriminant analysis of the least-squares (OPLS-DA) allowed twelve metabolites to be potential biomarkers of differentiation among the clones studied. Namely, the triene-(17:3)-anacardic acid found on CCP 76 and BRS 189 clones, respectively, is the main candidate for biomarker of resistance. While catechin, B-type procyanidin isomers, and procyanidin dimer monogallate identified in BRS 265 are significant potential biomarkers of susceptibility.

Black mold, a disease caused by the fungus Pilgeriella anacardii Arx & Müller, affects cashews (Anacardium occidentale). Some cashew clones are more resistant to the pathogen; however, little is known about the chemical profile responsible for this trait. The investigation of volatile organic compounds (VOCs) from leaves of dwarf cashew clones resistant (BRS 226 and BRS 265) and susceptible (CCP 76 and BRS 189) to the pathogen was carried out. Leaves were collected during the months of disease incidence and decline (March to July 2019, Brazil), and VOCs were analyzed by gas chromatography-mass spectrometry (GC-MS) combined with chemometric tools. The GC-MS analysis tentatively identified 96 compounds. Partial least squares discriminant analysis (PLS-DA), orthogonal partial least squares discriminant analysis (OPLS DA), hierarchical cluster analysis (HCA), and ROC curves analysis were useful in dividing VOCs into distinct resistance and associated chemical susceptibility groups for different clones. The VOCs in the leaves of the resistant clones were identified as alcohols and aldehydes containing six carbons: (E)-hex-2-enal, hex-3-en-1-ol, (Z)-hex-2-en-1-ol, (E)-hex-2-en-1-ol, and hexan-1-ol. Moreover, α-pinene, pseudolimonene, α-phellandrene, β-myrcene, sylvestrene, β-cis-ocimene, methyl salicylate, myrtenol, α-copaene, γ-muurolene, germacrene D, valencene, and germacrene B were also detected in these samples and may be candidate chemical biomarkers for cashew resistance to P. anacardii.