Trichoderma Enhances Net Photosynthesis, Water Use Efficiency, and Growth of Wheat (Triticum aestivum L.) under Salt Stress.

Abraham Mulu Oljira,Xiaojing Liu,Huicheng Zhao,Xinzhen Wang,Hongyong Sun,Tatoba R Waghmode,Tabassum Hussain,Binbin Liu

doi:10.3390/microorganisms8101565

Abstract

Soil salinity is one of the most important abiotic stresses limiting plant growth and productivity. The breeding of salt-tolerant wheat cultivars has substantially relieved the adverse effects of salt stress. Complementing these cultivars with growth-promoting microbes has the potential to stimulate and further enhance their salt tolerance. In this study, two fungal isolates, Th4 and Th6, and one bacterial isolate, C7, were isolated. The phylogenetic analyses suggested that these isolates were closely related to Trichoderma yunnanense, Trichoderma afroharzianum, and Bacillus licheniformis, respectively. These isolates produced indole-3-acetic acid (IAA) under salt stress (200 mM). The abilities of these isolates to enhance salt tolerance were investigated by seed coatings on salt-sensitive and salt-tolerant wheat cultivars. Salt stress (S), cultivar (C), and microbial treatment (M) significantly affected water use efficiency. The interaction effect of M x S significantly correlated with all photosynthetic parameters investigated. Treatments with Trichoderma isolates enhanced net photosynthesis, water use efficiency and biomass production. Principal component analysis revealed that the influences of microbial isolates on the photosynthetic parameters of the different wheat cultivars differed substantially. This study illustrated that Trichoderma isolates enhance the growth of wheat under salt stress and demonstrated the potential of using these isolates as plant biostimulants.

Highlights

Soil salinization is recognized as one of the most serious threats to agricultural production [1], affecting more than one billion hectares worldwide [2]
Our results demonstrated that the net photosynthesis rate of plants grown from noncoated and Bacillus-coated seeds decreased under salt stress, but plants grown from seeds coated with Trichoderma isolates showed substantial biomass improvement in this regard
Our results revealed that the photosynthesis rates in plants grown from seeds coated with Bacillus were unambiguously decreased under salt stress exposure

Summary

Introduction

Soil salinization is recognized as one of the most serious threats to agricultural production [1], affecting more than one billion hectares worldwide [2]. Increased salinization is expected to affect 50% of arable land by the year 2050 [3]. Previous studies have revealed the detrimental effect of salt stress on many aspects of plant gas exchange, including net photosynthesis, transpiration rates, intercellular CO2, stomatal conductance, and water use efficiency [4,5]. The enhancement of photosynthetic gas exchange efficiency under stressful environmental conditions is critical for yield improvement [6]. The improvement of net photosynthesis and water use efficiency has attracted researchers’ attention as possible approaches to optimize carbon assimilation in food crop production [7,8]. Metabolic acclimation via the synthesis of compatible solutes, including proline, has shown the potential to minimize salt-induced oxidative stress, protect the integrity of photosynthetic machinery (thylakoids and plasma membranes), repair damage to photosystem II, and scavenge reactive oxygen species (ROS) [9,10]

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