Covering soybean leaves with cellulose nanofiber changes leaf surface hydrophobicity and confers resistance against Phakopsora pachyrhizi

Abstract

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi, an obligate biotrophic fungal pathogen, is the most devastating soybean production disease worldwide. Currently, timely fungicide application is the only means to control ASR in the field. We investigated cellulose nanofiber (CNF) application on ASR disease management. CNF-treated leaves showed reduced lesion number after P. pachyrhizi inoculation compared to control leaves, indicating that covering soybean leaves with CNF confers P. pachyrhizi resistance. We also demonstrated that formation of P. pachyrhizi pre-infection structures including germ-tubes and appressoria, and also gene expression related to these formations, such as chitin synthases (CHSs), were significantly suppressed in CNF-treated soybean leaves compared to control leaves. Moreover, contact angle measurement revealed that CNF converts soybean leaf surface properties from hydrophobic to hydrophilic. These results suggest that CNF can change soybean leaf surface hydrophobicity, conferring resistance against P. pachyrhizi, based on the reduced expression of CHSs, as well as reduced formation of pre-infection structures. This is the first study to investigate CNF application to control field disease.

Exogenous double‐stranded RNA inhibits the infection physiology of rust fungi to reduce symptoms in planta

“…Spores of fungal foliar pathogens anchor themselves, germinate, and concentrate their cytoplasm in appressoria to build force and penetrate leaf surfaces through stomata (Wynn, 1975). The interface between leaves and fungal spores in plant–pathogen interactions has been examined on artificial leaf‐like surfaces made from polystyrene (Bernstein & Jones, 1969; Collins & Read, 1997; Dickinson, 1949; Wynn, 1975), silicone (Lee & Dean, 1994), and cellulose nanofibre (Saito et al, 2021). Artificial leaf‐like surfaces were used to assess the effect of environmental factors on pathogen infection (Doan & Leveau, 2015) and to study how dsRNA‐induced RNAi impacts the infection process of rust fungi (Saito et al, 2022).…”