Covering Soybean Leaves With Cellulose Nanofiber Changes Leaf Surface Hydrophobicity and Confers Resistance Against Phakopsora pachyrhizi.

Haruka Saito,Takako Ishiga,Viet Tru Nguyen,Giyu Usuki,Yasuhiro Ishiga,Nanami Sakata,Eiji Yamamura,Nanami Shiraishi,Yuji Yamashita

doi:10.3389/fpls.2021.726565

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 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.

Highlights

Diseases in important crop plants have a significant negative impact on agricultural productivity
We show that a specific cellulose nanofiber (CNF) property can change soybean leaf surface hydrophobicity, resulting in reduced formation of pre-infection structures associated with reduced P. pachyrhizi infection
CNF-treated leaves showed significantly reduced lesion number compared to control leaves (Figure 1B). These results indicate that covering soybean leaves with CNF confers resistance against P. pachyrhizi

Summary

Introduction

Diseases in important crop plants have a significant negative impact on agricultural productivity. Asian soybean rust (ASR) caused by Phakopsora pachyrhizi, an obligate biotrophic fungal pathogen, is the most devastating soybean production disease worldwide, with an estimated crop yield loss of up to 90%. Godoy et al (2016) reported that the losses caused by ASR were over 2 billion US dollars in Brazil annually between 2003 and 2014. Most rust fungi have a high host specificity, the P. pachyrhizi host range is broad and can infect diverse leguminous plant leaves in the field (Slaminko et al, 2008). Unlike cereal rust fungi that penetrates through stomata (Bolton et al, 2008), P. pachyrhizi directly penetrates into host plant epidermal cells by an appressorial peg.

Methods

Results

Conclusion