Coinfection by Lasiodiplodia pseudotheobromae and Pestalotiopsis mangiferae suppresses defense gene expression in Mangifera indica

Background/Objective. Dieback is an important fungal disease in mango trees (Mangifera indica) worldwide, associated with several fungal species. In Mexico, Lasiodiplodia pseudotheobromae and Pestalotiopsis mangiferae are associated with branch dieback symptoms, frequently occurring as coinfections. However, the specific response of mango genes to single and coinfection by these pathogens remains unknown. Therefore, the objective of this study was to analyze the expression patterns of selected defense-related genes in 'Manila' mango during single and coinfection with L. pseudotheobromae and P. mangiferae. Experimental development. Mango branches of Manila variety were inoculated with isolates of L. pseudotheobromae S10, and P. mangiferae MN2 in independent and coinfection treatments. The experiment was established under a completely randomized design with four replicates per treatment. Gene expression was evaluated at 1, 3, 5, and 7 days post inoculation (DPI). Total RNA was extracted from infected tissues, and relative expression levels of pathogenesis-related 1 (PR1), ethylene responsive factor 61 (ERF61), NBS-LRR, and chalcone synthase (CHS) genes were determined by quantitative real-time PCR using the 2-ΔΔCT method. Expression data were analyzed by one-way analysis of variance, and mean comparisons were performed using Tukey’s test (p ≤ 0.05). Results. The coinfection treatment showed lower transcript accumulation of the evaluated defense-related genes than the individual infection treatments (p = 0.05). The highest PR1 expression was detected during L. pseudotheobromae S10 infection, reaching values approximately 10-fold higher than those observed in P. mangiferae MN2 infection and coinfection at 7 DPI. Conversely, ERF61 showed greater early induction during P. mangiferae MN2 infection, with expression level 9-fold higher than that induced by L. pseudotheobromae S10 at 1 DPI. The NBS-LRR gene was expressed during individual infections, whereas its transcript accumulation was not detected in coinfected tissues. Likewise, CHS expression was higher during L. pseudotheobromae S10 infection, with levels 2.5-fold higher than those detected during coinfection at 1 DPI. Conclusion. Coinfection of L. pseudotheobromae and P. mangiferae reduced the expression of PR1, NBS-LRR, and CHS compared with individual infections, suggesting a greater suppression of specific plant defense genes, which may result in an increase in dieback disease severity. Further research is needed to deepen the understanding of the molecular mechanisms and the effects of coinfection on host defense responses and disease progression.