Alleviation of Salt Stress in Upland Rice (Oryza sativa L. ssp. indica cv. Leum Pua) Using Arbuscular Mycorrhizal Fungi Inoculation.

Rujira Tisarum,Harminder Pal Singh,Thapanee Samphumphuang,Suriyan Cha-Um,Panarat Thongpoem,Kanyamin Polispitak,Cattarin Theerawitaya

doi:10.3389/fpls.2020.00348

Abstract

Arbuscular mycorrhizal fungi (AMF) symbionts not only promote the growth of host plant but also alleviate abiotic stresses. This study aimed to investigate the putative role of AMF in salt stress regulation of upland pigmented rice cv. Leum Pua (LP) comparing with Pokkali salt tolerant (positive check). In general, LP is a variety of glutinous rice that contains anthocyanin pigment in the black pericarp, due to which it possesses high antioxidant activities compared to non-pigmented rice. Pot experiment was conducted to evaluate the impact of inoculated AMF, Glomus etunicatum (GE), Glomus geosporum (GG), and Glomus mosseae (GM) strains, in the LP plantlets subjected to 0 (control) or 150 mM NaCl (salt stress) for 2 weeks in comparison with Pokkali (a salt tolerant rice cultivar), which was maintained as a positive check. Root colonization percentage under NaCl conditions ranged from 23 to 30%. Na+ content in the flag leaf tissues was increased to 18–35 mg g–1 DW after exposure to 150 mM NaCl for 14 days in both inoculated and un-inoculated LP plants, whereas Na:K ratio was very low in cv. Pokkali. Interestingly, sucrose content in the flag leaf tissues of un-inoculated LP plants under salt stress was increased significantly by 50 folds over the control as an indicator of salt stress response, whereas it was unchanged in all AMF treatments. Fructose and free proline in GE inoculated plants under salt stress were accumulated over control by 5.75 and 13.59 folds, respectively, for osmotic adjustment of the cell, thereby maintaining the structure and functions of chlorophyll pigments, Fv/Fm, ΦPSII, and stomatal function. Shoot height, flag leaf length, number of panicles, panicle length, panicle weight, and 100-grain weight in GE inoculated plants of cv. LP under salt stress were maintained similar to cv. Pokkali. Interestingly, cyanidin-3-glucoside (C3G) and peonidin-3-glucoside (P3G) in the pericarp of cv. LP were regulated by GE inoculation under salt stress conditions. In summary, AMF-inoculation in rice crop is a successful alternative approach to reduce salt toxicity, maintain the yield attributes, and regulate anthocyanins enrichment in the pericarp of grains.

Highlights

Saline soil affects agricultural productivity in several regions of the world including United States, Argentina, Australia, China, Egypt, India, Iran, Iraq, Pakistan, and Thailand
Glomus mosseae (GM), Glomus geosporum (GG), Glomus intraradices, Acaulospora sp., and Scutellospora sp. are Arbuscular mycorrhizal fungi (AMF) species that generally colonize with rice (Gosling et al, 2006; Maiti et al, 2013; Zhang et al, 2014; Tisarum et al, 2019)
Ion homeostasis, compartmentalization, and Na+ translocation from root to shoot via apoplastic and/or symplastic routes have been regulated by AMFinoculation (Evelin et al, 2009; Porcel et al, 2012; He and Huang, 2013; Porcel et al, 2016; Yadav et al, 2017; Evelin et al, 2019)

Summary

Introduction

Saline soil affects agricultural productivity in several regions of the world including United States, Argentina, Australia, China, Egypt, India, Iran, Iraq, Pakistan, and Thailand (i.e., an area > 800 million ha; Rengasamy, 2010). AMF colonizes with root organs of the host plant, and regulates its photosynthetic abilities, growth characteristics, and abiotic stress tolerance (Panneerselvam et al, 2017; Basu et al, 2018; Mbodj et al, 2018). Better defense responses in terms of the higher production of free proline, glycine betaine, and soluble sugars in AMF inoculated plants against salt stress have been reported (Campanelli et al, 2013; Evelin et al, 2013; Garg and Baher, 2013; Talaat and Shawky, 2014). Several antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), are upregulated as salt defense responses in AMF inoculated plants under salt stress (Borde et al, 2011; Ruiz-Lozano et al, 2012; Evelin and Kapoor, 2014; Chang et al, 2018)

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