Plant growth, ion accumulation and antioxidant enzymes of endophyte-infected and endophyte-free tall fescue to salinity stress

Authors: PAN, LU - Inner Mongolian Agriculture University; CUI, SHIMAO - Inner Mongolian Agriculture University; Dinkins, Randy; JIANG, YIWEI - Purdue University

Submitted to: Acta Physiologiae Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2021
Publication Date: 6/4/2021
Citation: Pan, L., Cui, S., Dinkins, R.D., Jiang, Y. 2021. Plant growth, ion accumulation and antioxidant enzymes of endophyte-infected and endophyte-free tall fescue to salinity stress. Acta Physiologiae Plantarum. 43. Article 95. https://doi.org/10.1007/s11738-021-03268-4.
DOI: https://doi.org/10.1007/s11738-021-03268-4

Interpretive Summary: Soil salinity is a major problem negatively affecting crop growth in many areas of the world, and selecting for traits in plant varieties that tolerate salt stress is a major research goal. Previous work has demonstrated that the presence of the tall fescue endophyte, Epichloë coenophiala, contributes to the ability of tall fescue to better withstand heat and water stress. The following research was undertaken to characterize the contribution of the tall fescue endophyte in regards to salt stress tolerance. A genetically identical clone, with (E+) and without (E-) the endophyte, was subjected to two levels of salt stress, along with control plants to characterize the response. The salt stress decreased plant height, leaf fresh weight (LFW), leaf dry weight (LDW), leaf water content (LWC), and increased sodium (Na+) content, but E+ plants had significantly higher LFW, LDW, and LWC under both salt treatments and lower Na+ than E- plants under the high salt treatment. Photosynthetic efficiency, measured by using chlorophyll fluorescence (Fv/Fm), total soluble protein (TSP), and peroxidation enzyme activities, namely superoxide dismutase, catalase, and ascorbate peroxidase, remained unchanged in E+ plants, but Fv/Fm and TSP were reduced and enzyme activities were elevated in E- plants under salt treatment. The results indicated that endophyte promoted salinity tolerance in tall fescue by maintaining higher growth and photosynthetic efficiency and lowering Na+ accumulation and lipid peroxidation. This work confirms that the presence of the endophyte can aid in growth of tall fescue under salt stress, thereby demonstrating an additional benefit for the presence of endophyte in persistence of tall fescue under different stress environments.

Technical Abstract: Endophyte-mediated salinity tolerance is largely unknown in tall fescue [(Schedonorus arundinaceus (Schreb.)]. The objective of this study was to investigate growth, ion accumulation, and antioxidant responses of tall fescue infected by the endophyte Epichloë coenophiala to different levels of salinity stress. Endophyte-infected (E+) and endophyte-free (E-) grass plants were subjected to 0 (control), 100- and 200-mM NaCl for 10 d in a greenhouse, respectively. Salinity stress decreased plant height, leaf fresh weight (LFW), leaf dry weight (LDW), leaf water content (LWC), and increased Na+ content, but E+ plants had significantly higher LFW, LDW, and LWC under both NaCl treatments and lower Na+ than E- plants under 200 mM NaCl. Salinity stress decreased K+ and Mg2+ and did not alter P, and increased Ca2+ in E+ plants and caused no change in Ca2+ in E- plants; however, endophyte had no effects on these elements. Chlorophyll fluorescence (Fv/Fm), total soluble protein (TSP), malondialdehyde (MDA), and activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) remained unchanged in E+ plants, but Fv/Fm and TSP were reduced and MDA and enzyme activities were elevated in E- plants under 200 mM NaCl, whereas E+ plants had significantly higher Fv/Fm and TSP and lower MDA, SOD and APX activities than E- plants. Peroxidase activities increased in E+ plants under 200 mM NaCl and in E- plants under both NaCl treatments. The results indicated that endophyte-promoted salinity tolerance in tall fescue through maintaining higher growth and photochemical efficiency and lowering Na+ accumulation and lipid peroxidation. The significantly induced antioxidant enzyme activities and lipid peroxidation in E- plants suggested a possibly enhanced oxidative injury in endophyte-free plants exposed to a high level of salinity stress.