Evaluation of Salt Tolerance in Italian Ryegrass at Different Developmental Stages

Yan Xie,Hua Yu,Ye Huang,Xiaoyan Sun,Jinmin Fu,Maurice Amee,Liang Chen,Xiaoying Liu,Xiaoning Li

doi:10.3390/agronomy11081487

Abstract

Soil salinity is one of the major abiotic stresses that continues to threaten plant growth and agricultural productivity. Screening germplasm with salinity tolerance is therefore necessary. This study was designed to evaluate salt tolerance based on the integrated tolerance index. Fifteen Italian ryegrass cultivars were used to evaluate the degree of genotypic variation in salt tolerance at the germination and vegetative growth stages of plant development. Evident variations in salt tolerance were observed at the germination stage under 255 mM NaCl treatment. Root growth rate, chlorophyll content, and germination rates played a vital role in determining salt tolerance. Based on combined attributes at the germination and vegetative growth stages, Gongniu, Chuangnong, Splendor, and Abundant were identified as the most tolerant cultivars. Furthermore, the constant crude protein, lower neutral detergent fiber, and acid detergent fiber contents were measured under salinity. Compared to the control, the cultivars Tetragold, Abundant, Splendor, Muyao, Harukaze, Tegao, Dongmu 70, and Doraian were identified to have high forage quality under salt stress. Finally, we selected Splendor and Abundant as the cultivars that expressed the highest degree of salt tolerance based on combined attributes related to germination, salt tolerance, and overall forage quality. In addition, gene expression analysis between salinity tolerant and sensitive cultivars revealed that the gene response to photosystem and carbohydrate synthesis may have played a mediating role in providing tolerance to salt stress.

Highlights

The salinity of soil or water is a major abiotic stress that hinders plant growth and limits the production capabilities of agricultural soils worldwide [1]
The final germination rates (GR) of cultivars Tegao and Big Boss dropped below 50% under 255 mM NaCl treatment
The method demonstrated in this study, i.e., cluster group ranking of cultivars based on multiple characters and D value, can be applied in salt-tolerance breeding to evaluate salt tolerance among cultivars with great advantage over conventional methods

Summary

Introduction

The salinity of soil or water is a major abiotic stress that hinders plant growth and limits the production capabilities of agricultural soils worldwide [1]. More than 800 million hectares of land are affected by salt, equating to more than 6% of the world’s total land area [2]. In China, 100 million hectares of soil are affected by salt and the area of saline land is increasing every year [3]. The identification of salt-tolerant plants and their cultivation could be a promising solution for land reclamation with saline soils. Collecting and assessing germplasm that is suitable for saline soils is the first step in finding genetic variation in salt tolerance. Research on salt tolerance in forage species has become increasingly important in saline soils. In China, only marginal land, such as saline soils, is available for planting forage species due to competition between the increasing population and decreasing farmland. There is an increasingly high need for genetic improvement of salt-tolerant forage species

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