Draft Genome Sequence of the Halophilic Strain Citrobacter braakii AN-PRR1, Isolated from Rhizospheric Soil of Rice (Oryza sativa L.) from Pakistan

Citrobacter braakii AN-PRR1 is a potential salt-tolerant, plant growth-promoting rice rhizobacterium isolated from Pakistani soil. The 4.9-Mb draft genome sequence contributes to its taxonomic classification and will reveal the genes putatively responsible for its osmoprotectant and plant growth-promoting activity.

Plant growth-promoting activity in bean plants of endophytic bacteria isolated from Echeveria laui

Echeveria laui (Crassulaceae) is commonly commercialized due to its drought-tolerance capacity and to its rosette-shaped aesthetics. Since endophytes associated with plants from a dry or arid environment have scarcely been analyzed as yet, current research comprises the isolation of leaf endophytic bacteria from E. laui (one five-year-old and one two-year-old plants) investigating plant growth-promoting endophytic bacteria which may solubilize phosphate, fix nitrogen, produce exopolysaccharides/IAA and antagonize phytopathogens. Isolation by the maceration methodology provided a colonization rate of 1.98 x109 CFU g-1 for the two-year-old plant and 1.14 x 1010 CFU g-1 for the five-year-old one. All 40 isolates evaluated showed in vitro plant growth-promoting agent’s abilities, with emphasis on EG04, ELG18, and ELP06. The capacity of the three best bacterial isolates were evaluated under greenhouse conditions in common and black bean (Phaseolus vulgaris L.) plants. Based on the sequencing of the 16S rRNA region and phylogenetic analysis, the three endophytes were identified as Pantoea sp. (ELG04 and ELG18) and Erwinia sp. (ELP06). Under greenhouse conditions, statistically significant differences were found among the plants treated with the three endophytes when compared to control plants for fresh and dry shoot, root biomass and length.

Novel Effects of Leonardite-Based Applications on Sugar Beet

The present study aimed to explore the effects of foliar application of a leonardite-based product on sugar beet (Beta vulgaris L.) plants grown in the field. The approach concerned the evaluation of the community compositional structure of plant endophytic bacteria through a metabarcoding approach, the expression level of a gene panel related to hormonal metabolism and signaling, and the main sugar beet productivity traits. Results indicated that plants treated with leonardite (dosage of 2,000 ml ha–1, dilution 1:125, 4 mg C l–1) compared with untreated ones had a significant increase (p < 0.05) in (i) the abundance of Oxalicibacterium spp., recognized to be an endophyte bacterial genus with plant growth-promoting activity; (ii) the expression level of LAX2 gene, coding for auxin transport proteins; and (iii) sugar yield. This study represents a step forward to advance our understanding of the changes induced by leonardite-based biostimulant in sugar beet.

Case study of a rhizosphere microbiome assay on a bamboo rhizome with excessive shoots

Young Moso bamboo shoots are a very popular seasonal food. Bamboo is an important source of income for farmers and the value for cultivation has recently been estimated to $30,000 per hectare. A rare and valuable phenomenon has recently appeared where dozens of adjacent buds within a single Moso bamboo rhizome have grown into shoots. Due to its rarity, this phenomenon, which is of practical importance for the production of edible shoots, has not been scientifically studied. We report the occurrence of a rhizome with 18 shoots, of which the microbiome were analyzed, using rhizomes having one or no shoots as controls. The community of prokaryotes, but not fungi, correlated with the shoot numbers. Burkholderia was the most abundant genus, which negatively correlated with rhizome shoot number, while Clostridia and Ktedonobacteria positively correlated with many shoots. Two Burkholderia strains were isolated and their plant-growth promoting activity was tested. The isolated Burkholderia strains attenuated the growth of bamboo seedlings. Analysis of collected events of enhanced shoot production in China showed no evidence that enhanced shoot development was heritable. Overall, our data provides a firsthand study on excessive shoot development of bamboo.

Antifungal and plant growth promoting activity with Bacillus amyloliquefaciens in Aeonium subs.

In this work, the biostimulant and biocontrol capacity of Bacillus amyloliquefaciens in succulent plants such as Aeonium was evaluated. The specific objectives were in particular: (i) Evaluate whether the use of this bacterium can increase the growth rate of Aeonium plants that typically have a slow growth cycle; (ii) evaluate if the use of B. amyloliquefaciens can lead to increased plant resistance to Fusarium oxysporum; (iii) considered if utilization of B. amyloliquefaciens allows for increased plant resistance to water and nutrient stress. The experimentation showed a significant improvement of the agronomic parameters analyzed on all Aeonium plants treated with Bacillus amyloliquefaciens. In general there was a significant increase in plant height, number of leaves, vegetative and root weight, number of new shoots. In addition, Aeonium goochiae and sunburst show a better protection against the fungus Fusarium oxysporum. The trial also highlighted the ability of B. amyloliquefaciens to guarantee a productive and qualitative production of the plants even under conditions of reduced water and nutritional resources. Plants, thanks to the interaction with soil microorganisms, can reach higher nutrient and water resources, resulting in greater resistance to abiotic stresses and better quality in the cultivation cycle.

Synthesis of New Steroidal Carbamates with Plant-Growth-Promoting Activity: Theoretical and Experimental Evidence

A priority of modern agriculture is to use novel and environmentally friendly plant-growth promoter compounds to increase crop yields and avoid the indiscriminate use of synthetic fertilizers. Brassinosteroids are directly involved in the growth and development of plants and are considered attractive candidates to solve this problem. Obtaining these metabolites from their natural sources is expensive and cumbersome since they occur in extremely low concentrations in plants. For this reason, much effort has been dedicated in the last decades to synthesize brassinosteroids analogs. In this manuscript, we present the synthesis and characterization of seven steroidal carbamates starting from stigmasterol, β-sitosterol, diosgenin and several oxygenated derivatives of it. The synthesis route for functionalization of diosgenin included epoxidation and epoxy opening reactions, reduction of carbonyl groups, selective oxidation of hydroxyl groups, among others. All the obtained compounds were characterized by 1H and 13C NMR, HRMS, and their melting points are also reported. Rice lamina inclination test performed at different concentrations established that all reported steroidal carbamates show plant-growth-promoting activity. A molecular docking study evaluated the affinity of the synthesized compounds towards the BRI1-BAK1 receptor from Arabidopsis thaliana and three of the docked compounds displayed a binding energy lower than brassinolide.