Transcriptomic and metabolomic analyses reveal that lignin biosynthesis contributes to bayberry (Myrica rubra) defence responses against twig blight

Twig blight is a highly destructive disease primarily caused by Pestalotiopsis versicolor. It affects bayberry (Myrica rubra) cultivation and production. However, the molecular and regulatory defence responses to twig blight remain unclear. We inoculated a susceptible cultivar bayberry variety with P. versicolor XJ27 and carefully profiled the disease development. The bayberry disease index increased sharply following inoculation. We conducted integrative transcriptomic and metabolomic analyses to track key genes and secondary metabolomic changes in susceptible bayberry leaves. Herein, we identified 9588 differentially expressed genes (DEGs) and 748 differentially accumulated metabolites (DAMs). Of these, seven structural genes and seven metabolites (including L-phenylalanine, coniferin, p-coumaric acid, cinnamaldehyde, eleutheroside B, ferulaldehyde, and isoeugenol) related to lignin biosynthesis markedly increased following pathogen infection. These observations suggest that lignin biosynthesis may facilitate bayberry defence responses to twig blight. Quantitative real-time PCR analysis further confirmed the higher expression levels of pivotal lignin synthesis genes in infected leaves. In addition, higher foliar lignin levels and increased xylem formation in infected leaves provided evidence that lignin synthesis was enhanced during bayberry response to twig blight. These findings not only provide effective management strategies for bayberry twig blight but also promote the breeding of high-quality resistant varieties.