Characterization of Plant Growth-Promoting Traits and Inoculation Effects on Triticum durum of Actinomycetes Isolates under Salt Stress Conditions

Abstract

This study aimed to characterize the halotolerant capability, in vitro, of selected actinomycetes strains and to evaluate their competence in promoting halo stress tolerance in durum wheat in a greenhouse experiment. Fourteen isolates were tested for phosphate solubilization, indole acetic acid, hydrocyanic acid, and ammonia production under different salt concentrations (i.e., 0, 0.25, 0.5, 0.75, 1, 1.25, and 1.5 M NaCl). The presence of 1-aminocyclopropane-1-carboxylate deaminase activity was also investigated. Salinity tolerance was evaluated in durum wheat through plant growth and development parameters: shoot and root length, dry and ash-free dry weight, and the total chlorophyll content, as well as proline accumulation. In vitro assays have shown that the strains can solubilize inorganic phosphate and produce indole acetic acid, hydrocyanic acid, and ammonia under different salt concentrations. Most of the strains (86%) had 1-aminocyclopropane-1-carboxylate deaminase activity, with significant amounts of α-ketobutyric acid. In the greenhouse experiment, inoculation with actinomycetes strains improved the morpho-biochemical parameters of durum wheat plants, which also recorded significantly higher content of chlorophylls and proline than those uninoculated, both under normal and stressed conditions. Our results suggest that inoculation of halotolerant actinomycetes can mitigate the negative effects of salt stress and allow normal growth and development of durum wheat plants.

PGPB Improve Photosynthetic Activity and Tolerance to Oxidative Stress in Brassica napus Grown on Salinized Soils

“…On the contrary, plants under salt stress inoculated with B. ambifaria and H. seropedicae showed a reduction in chlorophyll content but an enhancement in carotenoids (Table 3). Our results are in accordance with previous studies that showed an increase, compared with saline control, in the amount of chlorophyll and carotenoids in plants of Brassica napus [52] and Triticum durum [50] exposed to salt stress and inoculated with PGPB strains. The increase in photosynthetic pigments in PGPB-inoculated plants suggests the capacity of bacterial inoculation to reduce the detrimental effects of salt, by ameliorating the activities of electron transporters associated with photosynthesis [60], as well as the biosynthesis of proteins and enzymes related to pigment stabilization [61].…”

“…In this study, all of the strains tested are IAA producers [31,33,49], and this may in part explain the elevated halotolerance detected. As suggested by some authors [50], plant inoculation with halotolerant bacteria strains can represent a good tool to improve plant fitness of salt-sensitive cultivars [51].…”

“…In addition, proper plant physiological responses to stress involve eliciting different stress response mechanisms. Under this perspective, bacterial metabolic activity may play a key role [16,18,33,50], leading to better plant responses to stress. Confirming these observations, the data reported in this study showed an increase in the growth of inoculated plants grown in saline soils [20,52].…”

Plant Beneficial Deep-Sea Actinobacterium, Dermacoccus abyssi MT1.1T Promote Growth of Tomato (Solanum lycopersicum) under Salinity Stress

“…Plant growth promoting bacteria, in particular actinobacteria, have been adopted to enhance crop production and alleviate salt stress in several plant species. Actinobacteria have been reported to promote plant growth under salt stress in tomato [ 14 , 15 , 16 , 17 ], soybean [ 18 , 19 ], wheat [ 20 , 21 ], alfalfa [ 22 ], and dwarf glasswort [ 23 ]. Recently, actinobacteria with plant growth promoting potential dwell in extreme saline environments such as marine sediments, mangrove, and halophyte are attracting research attention due to their adaptive features in such environments which are beneficial to plants under salinity stress.…”

Biocontrol of Soil-Borne Pathogens of Solanum lycopersicum L. and Daucus carota L. by Plant Growth-Promoting Actinomycetes: In Vitro and In Planta Antagonistic Activity

“…and Nocardiopsis spp. actinomycetes that have already been demonstrated to be used as biostimulants [15] and salt stress-tolerance agents [16]. Given these capabilities, we hypothesized that these strains could be valid biocontrol agents against fungal and bacterial pathogens.…”