Enzymes and secondary metabolites profiles of Gnomoniopsis smithogilvyi are affected by chestnut medium
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abstract
Chestnut tree (Castanea sativa Mill) is a crop with high economic and social importance in
Trás-os-Montes Region. The pre and post-harvest quality of its nuts can be affected by many
factors, being the lasses dueto fungi very large. During the last decade a new endophyte
fungus, Gnomoniopsis smithogilvyi, causing brown rot, has been isolated from both rotten and
healthy fruits, and its growth seems to be related with the increase of air temperatura and
rainfall during spring. The present study aims to understand the influence of chestnut substrate
on G. smithogilvyi biochemistry, in arder to develop strategies to reduce its incidence in the
fruit and improve the contrai of brown rot. lnitially, the presence of the enzymes involved in the
decomposition of chestnuts, such as amylase, proteases, carboxymethylcellulase (CMCase),
~-glucosidase, xylanase, among others, was investigated. Further, some hydrolase activities
were evaluated in two isolates of G. smithogilvyi incubated in potato (PDB) and chestnut media
(CM) along an incubation period (3, 7 and 14 days), in arder to study the effects "isolate",
"medium" and "incubation period" on enzymes production. Also, the synthesis of secondary
metabolites in fungai dry biomass was assessed by Liquid chromatography coupled to tandem
mass spectrometry (LC-MS/MS). Ali isolates produced the enzymes screened and, in general,
the enzyme production varied between the isolates (P< 0.0000), the media (P< 0.0000) and
along the incubation period (P< 0.0000). Amylase activity was positively correlated with
xylanase (P< 0.0001), CMCase (P< 0.0001), and Avicelase {P< 0.01), xylanase with CMCase
(P< 0.01) and ~-glucosidase with Avicelase (P< 0.0001 ). By contrast, ~-glucosidase was
negatively correlated with CMCase {P< 0.01 ). Twenty secondary metabolites were detected
along the incubation: eight in both isolates and media, tive and three only in isolates grew in
PD o r CM, respectively. Some of these metabolites had been associated with other fungi and
have known biological activities.
This work was suported by "ValorCast- Valorização da castanha e otimização da sua comercialização" (PDR2020-1.0.1-
FEADER-032034}, funded by Fundo Europeu Agrfcola de Desenvolvimento Rural (FEADER} and the Portuguesa Government (Ação
1.1 Grupos Operacionais, Medida 1. Inovação, PDR 2020- Programa de Desenvolvimento Rural do Continente). AS, IF, JGL, AAD, are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CITAB (UIDB/04033/2020) and PR to CIMO (UIDB/00690/2020).
