Abstract
Soil salinity is a serious problem worldwide that reduces agricultural productivity. Trichoderma longibrachiatum T6 (T6) has been shown to promote wheat growth and induce plant resistance to parasitic nematodes, but whether the plant-growth-promoting fungi T6 can enhance plant tolerance to salt stress is unknown. Here, we determined the effect of plant-growth-promoting fungi T6 on wheat seedlings’ growth and development under salt stress, and investigated the role of T6 in inducing the resistance to NaCl stress at physiological, biochemical, and molecular levels. Wheat seedlings were inoculated with the strain of T6 and then compared with non-inoculated controls. Shoot height, root length, and shoot and root weights were measured on 15 days old wheat seedlings grown either under 150 mM NaCl or in a controlled setting without any NaCl. A number of colonies were re-isolated from the roots of wheat seedlings under salt stress. The relative water content in the leaves and roots, chlorophyll content, and root activity were significantly increased, and the accumulation of proline content in leaves was markedly accelerated with the plant growth parameters, but the content of leaf malondialdehyde under saline condition was significantly decreased. The antioxidant enzymes-superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in wheat seedlings were increased by 29, 39, and 19%, respectively, with the application of the strain of T6 under salt stress; the relative expression of SOD, POD, and CAT genes in these wheat seedlings were significantly up-regulated. Our results indicated that the strain of T6 ameliorated the adverse effects significantly, protecting the seedlings from salt stress during their growth period. The possible mechanisms by which T6 suppresses the negative effect of NaCl stress on wheat seedling growth may be due to the improvement of the antioxidative defense system and gene expression in the stressed wheat plants.
Highlights
Salt stress is one of the major abiotic stresses that affects plant growth, development, and crop yield (Ma et al, 2012; Rivero et al, 2014)
Previous studies have demonstrated that a high level of salinity is one of the major environmental stress factors that causes biochemical alterations in plants, limits plant growth, and decreases plant productivity (Allakhverdiev et al, 2000; Mahmood et al, 2012)
Our results demonstrated that the NaCl treatment significantly inhibited wheat seedling growth and development after 15 days and the effect was alleviated substantially with the application of Trichoderma longibrachiatum T6 (T6)
Summary
Salt stress is one of the major abiotic stresses that affects plant growth, development, and crop yield (Ma et al, 2012; Rivero et al, 2014). A newer attempt is to apply exogenous compounds to decrease the negative effect of abiotic stress; this technique has been shown to increase plant tolerance to salt stress, such as using oligochitosan (Ma et al, 2012), nitric oxide and calcium nitrate (Tian et al, 2015), chitooligosaccharides (Zou et al, 2015), and jasmonic acid (Qiu et al, 2014) in wheat, as well as gibberllic acid and calcium chloride in linseed (Linum usitatissimum; Khan et al, 2010), and ascorbic acid in broad bean (Vicia faba; Younis et al, 2010). Trichoderma spp. is one of Abbreviations: AN, acid ninhydrin; ASA, aqueous sulfosalicylic acid; BSA, bovine serum albumin; CAT, catalase; CFUs, colony-forming units; GAA, glacial acetic acid; H2O2, hydrogen peroxide; MDA, malondialdehyde; PBS, phosphate buffer solution; POD, peroxidase; ROS, reactive oxygen species; SOD, superoxide dismutase; TBA, thiobarbituric acid; TCA, trichloroacetic acid; TTC, triphenyl tetrazolium chloride; T6, Trichoderma longibrachiatum T6
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