AUTHOR=Zugaib Maria , Almeida Dayanne Silva Monteiro de , de Santana Monique Reis , Macêdo Ferreira Monaliza , Santana Juliano Oliveira , Mangabeira Pedro Antônio Oliveira , Souza Jorge Teodoro de , Pirovani Carlos Priminho TITLE=Pre-infection Mechanisms on the Phylloplane: The First Biochemical Battlefield Between the Cacao Tree and Witches' Broom Pathogen JOURNAL=Frontiers in Agronomy VOLUME=4 YEAR=2022 URL=https://www.frontiersin.org/journals/agronomy/articles/10.3389/fagro.2022.871908 DOI=10.3389/fagro.2022.871908 ISSN=2673-3218 ABSTRACT=

The leaf surface combines biochemical substances and pre-existing morphological structures, as well as the presence of microorganisms. This dynamic environment constitutes a plant's initial defense, as well as the first contact of phytopathogens during invasion. Spore germination starts on the phylloplane and is a fundamental process for fungal development, and hence the establishment of disease. In this review, we address the phylloplane's innate defense mechanisms and biochemical reactions involved in the early stage of phytopathogenic fungal development. The focus is present the pre-infection molecular and biochemical processes of the interaction between Theobroma cacao and Moniliophthora perniciosa, showing how the defense mechanisms of the phylloplane can act to inhibit proteins involved at the beginning of fungal spore germination. We conclude that the phylloplane of the cocoa resistant genotype to M. perniciosa has performed chemical compounds, pre-existing morphological structures and the presence of microorganisms that participate in the pre-infection defense of the plant. Also, the inhibition of proteins involved in the germination mechanism of M. perniciosa basidiospores by chemical and structural compounds present in the cocoa phylloplane may decrease the disease index. Therefore, understanding how the phylloplane defense acts in the fungal spore germination process is essential to develop pre-infection control strategies for cacao plants against witches' broom.