Mucilage Polysaccharide Composition and Exudation in Maize From Contrasting Climatic Regions.

Meisam Nazari,Mutez Ali Ahmed,Michaela A Dippold,Asegidew Akale,Callum C Banfield,Sophie Riebeling,Kyle Mason-Jones,Margherita Crosta

doi:10.3389/fpls.2020.587610

Meisam Nazari, Mutez Ali Ahmed + Show 6 more

Open Access

https://doi.org/10.3389/fpls.2020.587610

Copy DOI

Abstract

Mucilage, a gelatinous substance comprising mostly polysaccharides, is exuded by maize nodal and underground root tips. Although mucilage provides several benefits for rhizosphere functions, studies on the variation in mucilage amounts and its polysaccharide composition between genotypes are still lacking. In this study, eight maize (Zea mays L.) genotypes from different globally distributed agroecological zones were grown under identical abiotic conditions in a randomized field experiment. Mucilage exudation amount, neutral sugars and uronic acids were quantified. Galactose (∼39–42%), fucose (∼22–30%), mannose (∼11–14%), and arabinose (∼8–11%) were the major neutral sugars in nodal root mucilage. Xylose (∼1–4%), and glucose (∼1–4%) occurred only in minor proportions. Glucuronic acid (∼3–5%) was the only uronic acid detected. The polysaccharide composition differed significantly between maize genotypes. Mucilage exudation was 135 and 125% higher in the Indian (900 M Gold) and Kenyan (DH 02) genotypes than in the central European genotypes, respectively. Mucilage exudation was positively associated with the vapor pressure deficit of the genotypes’ agroecological zone. The results indicate that selection for environments with high vapor pressure deficit may favor higher mucilage exudation, possibly because mucilage can delay the onset of hydraulic failure during periods of high vapor pressure deficit. Genotypes from semi-arid climates might offer sources of genetic material for beneficial mucilage traits.

Highlights

Plant roots have intensive physical, chemical and biological interactions with the surrounding soil (Haichar et al, 2008; Micallef et al, 2009; Bender et al, 2016; Leff et al, 2018)
Fucose, mannose, and arabinose were the major neutral sugars in the nodal root mucilage of the maize genotypes, whereas xylose and glucose were shown to be of minor proportion
This study investigated the polysaccharide composition, exudation amount, and saturation water content of nodal root mucilage of maize genotypes from three continents

Summary

Introduction

Plant roots have intensive physical, chemical and biological interactions with the surrounding soil (Haichar et al, 2008; Micallef et al, 2009; Bender et al, 2016; Leff et al, 2018). Maize (Zea mays L.) exudes mucilage both from its nodal and underground roots. Mucilage produced by the nodal roots of some maize landraces harbors nitrogen-fixing bacteria, contributing to the fixation of 29% to 82% of the plant’s nitrogen nutrition (Van Deynze et al, 2018; Amicucci et al, 2019; Bennett et al, 2020). This nitrogen fixation can increase maize yield and nitrogen use efficiency, especially in regions where agriculture suffers from poor soil fertility. Mucilage likely contributes to plant resistance to water stress, and may be important in water-limited environments (Ahmed et al, 2018b), and those with high vapor pressure deficit (VPD), where mucilage may delay the onset of hydraulic failure during drought (Grossiord et al, 2020)

Objectives

Methods

Results

Discussion

Conclusion