Priming maize resistance by its neighbors: activating 1,4-benzoxazine-3-ones synthesis and defense gene expression to alleviate leaf disease.

Xupo Ding,Chengyun Li,Shusheng Zhu,Xiahong He,Youyong Zhu,Huichuan Huang,Youcong Chuan,Min Yang

doi:10.3389/fpls.2015.00830

Abstract

Plant disease can be effectively suppressed in intercropping systems. Our previous study demonstrated that neighboring maize plants can restrict the spread of soil-borne pathogens of pepper plants by secreting defense compounds into the soil. However, whether maize plant can receive benefits from its neighboring pepper plants in an intercropping system is little attention. We examined the effects of maize roots treated with elicitors from the pepper pathogen Phytophthora capsici and pepper root exudates on the synthesis of 1,4-benzoxazine-3-ones (BXs), the expression of defense-related genes in maize, and their ability to alleviate the severity of southern corn leaf blight (SCLB) caused by Bipolaris maydis. We found that SCLB was significantly reduced after the above treatments. The contents of 1,4-benzoxazine-3-ones (BXs: DIBOA, DIMBOA, and MBOA) and the expression levels of BX synthesis and defense genes in maize roots and shoots were up-regulated. DIMBOA and MBOA effectively inhibited the mycelium growth of Bipolaris maydis at physiological concentrations in maize shoots. Further studies suggested that the defense related pathways or genes in maize roots and shoots were activated by elicitors from the P. capsici or pepper root exudates. In conclusion, maize increased the levels of BXs and defense gene expression both in roots and shoots after being triggered by root exudates and pathogen from neighboring pepper plants, eventually enhancing its resistance.

Highlights

The capability of some plants to affect neighboring plants has been well documented (Broz et al, 2010; Ratnadass et al, 2012)
Our experiments suggested that the accumulation of BXs and the expression levels of defense genes in maize roots and shoots were induced when maize roots triggered by the elicitors form the pathogen and root exudates from the neighboring pepper plants, which could enhance the resistance of maize against the above-ground leaf disease B. maydis
Induced Systemic Resistance against B. maydis To investigate the induced systemic resistance against B. maydis in maize leaves, the lesions on leaves infected by B. maydis were quantified after the maize roots were induced by the spore suspension (SP), spore lysis suspension (SL), culture suspension (CS), healthy pepper root exudates (HRE), and nosogenic pepper root exudates (NRE)

Summary

Introduction

The capability of some plants to affect neighboring plants has been well documented (Broz et al, 2010; Ratnadass et al, 2012). Certain plant diseases can be suppressed in biodiverse ecosystems (Zhu et al, 2000; Fan et al, 2010). This theory has been widely applied in traditional farming practices, such as intercropping, which has been practiced for 3000 years (de Albuquerque et al, 2010). The crop productivity is increased (Li et al, 2009) and the development of wind-dispersed and soil-borne diseases and nematodes is suppressed. One crop release volatile organic compounds (VOCs) to help other crop to suppress wind dispersed pathogens (Kishimoto et al, 2005; Chehab et al, 2008; Yi et al, 2009; Du Fall and Solomon, 2011; Naznin et al, 2014)

Methods

Results

Conclusion