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Mangrove (Avicennia marina) is a “green lung” tree growing along the Arabian Gulf coastline in the United Arab Emirates. Here, we aimed to determine the impact of the application of a commercial seaweed extract (SWE) biostimulant and endophytic actinobacterial isolates on growth performance and endogenous hormonal levels of mangroves. Therefore, we isolated endophytic plant growth-promoting (PGP) actinobacteria (PGPA) from mangrove roots and evaluated their potential as biological inoculants on mangrove seedlings under greenhouse and open-field nursery conditions. Seven salt-tolerant isolates had the ability to produce different levels of in vitro plant growth regulators (PGRs) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) and to solubilize phosphorus. Accordingly, only one isolate, Streptomyces tubercidicus UAE1 (St), was selected based on its relative superiority in displaying multiple modes of action and in successfully colonizing mangrove tissues for 15 weeks. In the greenhouse experiments, plants treated with St and SWE significantly (p < 0.05) improved dry biomass by 40.2% and 55.1% in roots and 42.2% and 55.4% in shoots, respectively, compared to seawater-irrigated non-treated mangrove plants (control). However, St+SWE caused a greater significant (p < 0.05) increase in dry weight of roots (67.6%) and shoots (65.7%) than did control plants. Following the combined treatment of St+SWE, in planta PGR levels were found to be greatly enhanced over the non-treated control plants grown in non-SWE supplemented sediments, or plants inoculated with only St without the supplementation with SWE, or with non-inoculated plants grown in sediments supplied with SWE only. This was evident from the significant (p < 0.05) increases in the photosynthetic pigments and production of PGRs, as well as the reduction in the endogenous ACC levels of plant tissues compared to those in other treatments. Tissue nutrient contents of seedlings also increased by at least two-fold in St+SWE treatment as compared to control. Similar effects were observed on all growth parameters under natural open-field nursery conditions. Combining St with SWE not only stimulates plant growth but also potentially has additive effects on mangrove ecosystem productivity in nutrient-impoverished soils in the Arabian coastal areas. This report is the first in the field of marine agriculture that uses SWE as a nutrient base for actinobacteria capable of producing PGRs and ACCD.

Mangrove forests in the Arabian Gulf are under continuous threat. To increase plantations of gray mangrove (Avicennia marina) in the United Arab Emirates (UAE), 27 endophytic actinobacterial isolates obtained from mangrove roots were in vitro pre-screened to detect the polyamines (PAs) [putrescine (Put), spermidine (Spd), and spermine (Spm)]. We also determined the abilities of the endophytic PA-producing actinobacterial isolates in enhancing the growth of A. marina under greenhouse conditions. Although three highly PA-producing isolates were recovered from inside mangrove root tissues, Streptomyces mutabilis UAE1 constantly colonized root and stem inner tissues for 12 weeks, suggesting an endophytic association between this actinobacterial isolate and mangrove seedlings. When roots were inoculated with S. mutabilis, mangrove growth was remarkably enhanced under gnotobiotic and greenhouse conditions. This was evident from the significant (P < 0.05) increases in dry weight and length of root (66.7 and 65.5%, respectively) and shoot (64.8 and 58.0%, respectively), number of branches (64.3%), total leaf area (40.2%), and photosynthetic pigments (54.5% chlorophyll a; 40.0% chlorophyll b; and 53.1% carotenoids) of mangrove compared to the PA-non-producing Streptomyces sp. or control treatment. Growth promotion in plants treated with S. mutabilis was also supported by significant (P < 0.05) elevations in the contents of mangrove in planta PAs, auxins, and cytokinins, accompanied by a decrease in abscisic acid levels. No difference was, however, detected in growth and amounts of PAs or any plant growth regulators (PGRs) in plants treated with or without the PA-non-producing isolate. Our findings indicate that plant growth parameters can be enhanced as a consequence of secretion of Put, Spd, and Spm by S. mutabilis resulting in regulation of endogenous PAs and other PGRs in mangrove tissues. This study is the first record that aims to improve sustainable agricultural management practices using plant growth promoting (PGP) actinobacteria, endophytic in mangrove tissues to promote mangrove growth under greenhouse conditions. Such research may allow this region to be a model to study the synergistic S. mutabilis–mangrove interactions and the future impacts on mangrove reforestation in the Arabian Gulf and elsewhere where mangrove forests are in threat.

Thirty-one endophytic streptomycete and non-streptomycete actinobacteria were isolated from healthy date palm root tissues. In vitro screening revealed that the antifungal action of isolate #16 was associated with the production of cell-wall degrading enzymes, whereas with diffusible antifungal metabolites in isolate #28, albeit their production of volatile antifungal compounds. According to the 16S rRNA gene sequencing, isolates #16 and #28 were identified as Streptomyces polychromogenes UAE2 (Sp; GenBank Accession #: OK560620) and Streptomyces coeruleoprunus UAE1 (Sc; OK560621), respectively. The two antagonists were recovered from root tissues until 12 weeks after inoculation, efficiently colonized root cortex and xylem vessels, indicating that the date palm roots are a suitable habitat for these endophytic isolates. At the end of the greenhouse experiments, the development of sudden decline syndrome (SDS) was markedly suppressed by 53% with the application of Sp and 86% with Sc, confirming their potential in disease management. Results showed that the estimated disease severity indices in diseased seedlings were significantly (p < 0.05) reduced from 4.75 (scale of 5) to 2.25 or 0.67 by either Sp or Sc, respectively. In addition, conidial numbers of the pathogen significantly (p < 0.05) dropped by 38% and 76% with Sp and Sc, respectively, compared to infected seedlings with F. solani (control). Thus, the suppression of disease symptoms was superior in seedlings pre-inoculated with S. coeruleoprunus, indicating that the diffusible antifungal metabolites were responsible for F. solani retardation in these plants. This is the first report of actinobacteria naturally existing in date palm tissues acting as microbial antagonists against SDS on date palm.

To manage stem canker disease on royal poinciana, actinobacterial isolates were used as biological control agents (BCAs) based on their strong in vitro inhibitory effects against Neoscytalidiumdimidiatum. Streptomyces griseorubens UAE2 and Streptomyces wuyuanensis UAE1 had the ability to produce antifungal compounds and cell-wall-degrading enzymes (CWDEs). Only S. griseorubens, however, restored the activity of 1-aminocyclopropane-1-carboxylate (ACC) deaminase (ACCD). In vivo apple fruit bioassay showed that lesion development was successfully constrained by either isolates on fruits inoculated with N. dimidiatum. In our greenhouse and container nursery experiments, S. griseorubens showed almost complete suppression of disease symptoms. This was evident when the preventive treatment of S. griseorubens significantly (p < 0.05) reduced the numbers of conidia of N. dimidiatum and defoliated leaves of royal poinciana seedlings to lesser levels than when S. wuyuanensis was applied, but comparable to control treatments (no pathogen). The disease management of stem canker was also associated with significant (p < 0.05) decreases in ACC levels in royal poinciana stems when S. griseorubens was applied compared to the non-ACCD-producing S. wuyuanensis. This study is the first to report the superiority of antagonistic actinobacteria to enhance their effectiveness as BCAs not only for producing antifungal metabolites and CWDEs but also for secreting ACCD.

Symptoms including shortness of breath, sputum clearing, and activities to increase strength and fitness can all be managed and controlled with the aid of physiotherapy. encouraging the opening of airways, enhancing mobility, encouraging rehabilitation, and helping to deliver efficient non-invasive ventilation services. In the case of obstructive bronchiolitis, the airways' interiors are smaller than usual due to ongoing inflammation and swelling. The ability of the lungs to efficiently and quickly expel air is hindered by this constriction. The lung's alveoli suffer damage and lose some of their flexibility in emphysema. As a result, they are challenging to empty. Airway narrowing is also a result of emphysema. The combination of non-stretchy alveoli due to emphysema and narrowed airways due to both obstructive bronchiolitis and emphysema prevents the lungs from emptying normally. This causes air to become trapped in the lungs. "Air trapping," or the inability to fully exhale, leads to abnormal expansion or hyperinflation of the lungs. [ABSTRACT FROM AUTHOR]