Antagonistic and plant growth promotion of rhizobacteria against Phytophthora colocasiae in taro

Open Access Article; Published online: 02 Dec 2022Taro leaf blight caused by Phytophthora colocasiae adversely affects the growth and yield of taro. The management of this disease depends heavily on synthetic fungicides. These compounds, however, pose potential hazards to human health and the environment. The present study aimed to investigate an alternative approach for plant growth promotion and disease control by evaluating seven different bacterial strains (viz., Serratia plymuthica, S412; S. plymuthica, S414; S. plymuthica, AS13; S. proteamaculans, S4; S. rubidaea, EV23; S. rubidaea, AV10; Pseudomonas fluorescens, SLU-99) and their different combinations as consortia against P. colocasiae. Antagonistic tests were performed in in vitro plate assays and the effective strains were selected for detached leaf assays and greenhouse trials. Plant growth-promoting and disease prevention traits of selected bacterial strains were also investigated in vitro. Our results indicated that some of these strains used singly (AV10, AS13, S4, and S414) and in combinations (S4+S414, AS13+AV10) reduced the growth of P. colocasiae (30−50%) in vitro and showed disease reduction ability when used singly or in combinations as consortia in greenhouse trials (88.75−99.37%). The disease-suppressing ability of these strains may be related to the production of enzymes such as chitinase, protease, cellulase, and amylase. Furthermore, all strains tested possessed plant growth-promoting traits such as indole-3-acetic acid production, siderophore formation, and phosphate solubilization. Overall, the present study revealed that bacterial strains significantly suppressed P. colocasiae disease development using in vitro, detached leaf, and greenhouse assays. Therefore, these bacterial strains can be used as an alternative strategy to minimize the use of synthetic fungicides and fertilizers to control taro blight and improve sustainable taro production

The Adsorption of Chlorofluoromethane on Pristine, Al‐, Ga‐, P‐, and As‐doped Boron Nitride Nanotubes: A PBC‐DFT, NBO, and QTAIM Study

The feasibility of detecting a Chlorofluoromethane (CFM) gas molecule on the outer surface of a pristine single‐walled boron nitride nanotube as well as Al‐, Ga‐, P‐, and As‐doped structures. A periodic boundary condition (PBC), within a density functional theory (DFT) method, using the Perdew, Burke, and Ernzerhof exchange‐correlation (PBE0) functional, together with a 6‐311G(d) basis set was used. Subsequently, the B3LYP, CAM−B3LYP, ωB97XD, and M06‐2X functionals were also employed to consider the single point energies. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) were implemented by using the PBE0/6‐311G(d). To explore the nature of the intermolecular interactions, density of state (DOS), Wiberg bond index (WBI), natural charge, natural electron configuration, donor–acceptor natural bond orbital interactions, the second‐order perturbation energies tests, and noncovalent interaction (NCI) analysis are performed. The sensitivity of the adsorption will be increased when the gas molecule interacts with decorated nanotubes; therefore, the change of electronic properties can be used to design suitable nanosensors

Bioprospecting of Beneficial Bacteria Traits Associated With Tomato Root in Greenhouse Environment Reveals That Sampling Sites Impact More Than the Root Compartment

Tomato is subject to several diseases that affect both field- and greenhouse-grown crops. To select cost-effective potential biocontrol agents, we used laboratory throughput screening to identify bacterial strains with versatile characteristics suitable for multipurpose uses. The natural diversity of tomato root–associated bacterial communities was bioprospected under a real-world environment represented by an intensive tomato cultivation area characterized by extraseasonal productions in the greenhouse. Approximately 400 tomato root–associated bacterial isolates, in majority Gram-negative bacteria, were isolated from three compartments: the soil close to the root surface (rhizosphere, R), the root surface (rhizoplane, RP), and the root interior (endorhizosphere, E). A total of 33% of the isolates produced siderophores and were able to solubilize phosphates and grow on NA with 8% NaCl. A total of 30% of the root-associated bacteria showed antagonistic activity against all the tomato pathogens tested, i.e., Clavibacter michiganesis pv. michiganensis, Pseudomonas syringae pv. tomato, Pseudomonas corrugata and Xanthomonas euvesicatoria pv. perforans, and Fusarium oxysporum f. sp. lycopersici. We found that the sampling site rather than the root compartment of isolation influenced bacterial composition in terms of analyzed phenotype. This was demonstrated through a diversity analysis including general characteristics and PGPR traits, as well as biocontrol activity in vitro. Analysis of 16S rRNA gene (rDNA) sequencing of 77 culturable endophytic bacteria that shared multiple beneficial activity revealed a predominance of bacteria in Bacillales, Enterobacteriales, and Pseudomonadales. Their in vitro antagonistic activity showed that Bacillus species were significantly more active than the isolates in the other taxonomic group. In planta activity against phytopathogenic bacteria of a subset of Bacillus and Pseudomonas isolates was also assessed