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Plant root and soil-associated microbiomes are influenced by niches, including bulk and rhizosphere soil. In this work, we collected bulk and rhizosphere soil samples at four potato developmental stages (leaf growth, flowering, tuber elongation and harvest) to identify whether rhizosphere microbiota are structured in a growth stage-dependent manner. The bacterial and fungal microbiota showed significant temporal differences in the rhizosphere and bulk soil. Rhizobacteria were most diverse at the tuber elongation stage, and dominant ASVs identified as Sphingomonas, Rhodanobacter, Sphingobium, Hyphomicrobium, and Solirubrobacter spp. In contrast, rhizosphere fungal diversity peaked at flowering stage, with Lecanicillium spp. being prominent. Furthermore, the abundance of saprophytic fungal genera, including Colletotrichum and Fusarium, and Alternaria, sharply increased at harvest stage, likely contributing to plant residue decomposition. Indicator taxa analysis highlighted the dominance of these genera at harvest. Network analysis revealed increased microbial complexity during the later growth stage, with 721 edges compared to 521 edges in the early growth stage. This increase included positive correlations between bacteria and negative correlations between bacteria and fungi. These changes suggest that microbial interactions become more interconnected and complex as potato plants mature. Our findings highlight the potential role of saprophytic fungi in shaping microbial dynamics during the later growth stage in rhizosphere soil. [ABSTRACT FROM AUTHOR]

Pseudomonads are cosmopolitan microorganisms able to produce a wide array of specialized metabolites. These molecules allow Pseudomonas to scavenge nutrients, sense population density and enhance or inhibit growth of competing microorganisms. However, these valuable metabolites are typically characterized one-molecule-one-microbe at a time, instead of being inventoried in large numbers. To index and map the diversity of molecules detected from these organisms, 260 strains of ecologically diverse origins were subjected to mass-spectrometry-based molecular networking. Molecular networking not only enables dereplication of molecules, but also sheds light on their structural relationships. Moreover, it accelerates the discovery of new molecules. Here, by indexing the Pseudomonas specialized metabolome, we report the molecular-networking-based discovery of four molecules and their evolutionary relationships: a poaeamide analogue and a molecular subfamily of cyclic lipopeptides, bananamides 1, 2 and 3. Analysis of their biosynthetic gene cluster shows that it constitutes a distinct evolutionary branch of the Pseudomonas cyclic lipopeptides. Through analysis of an additional 370 extracts of wheat-associated Pseudomonas, we demonstrate how the detailed knowledge from our reference index can be efficiently propagated to annotate complex metabolomic data from other studies, akin to the way in which newly generated genomic information can be compared to data from public databases.

Beneficial microorganisms play essential roles in soil fertility, plant nutrition, and health. In this study, we examined the potential of a collection of 138 bacterial strains to promote plant growth. The strains were isolated from the rhizosphere of two monocotyledonous and two dicotyledonous plant species and from bare fallow soil, all from the same site. Our interest in this study was to investigate the diversity and the potential for growth promotion in this collection of culturable bacteria. The most common trait was phosphorus (P) solubilization from aluminium phosphate (in 66.7% of the strains), whereas solubilization of P from phytic acid (6.5%) and from iron phosphate (5.8%) was the least common and they were only detected in bacterial strains from faba bean and oilseed rape. All bacterial strains inhibited the growth of Fusarium graminearum (from 5.4% to 87.2%). In total, 10 genera were identified among the strains by 16S rRNA sequencing and Pseudomonas was the most common in monocotyledonous plants and in bulk soil, while Stenotrophomonas was dominant in the rhizosphere of the dicotyledonous plants. Combinations of bacterial strains improved the spectrum of in vitro activity in most cases, however, wheat growth was generally lower. These strains have potential to be used as biofertilizers and/or biocontrol agents and further studies should be pursued to develop them into practical solutions for a more sustainable agricultural production. [ABSTRACT FROM AUTHOR]

Summary: Aphids, including the peach‐potato aphid, Myzus persicae, are major insect pests of agriculture and horticulture, and aphid control measures are limited. There is therefore an urgent need to develop alternative and more sustainable means of control. Recent studies have shown that environmental microbes have varying abilities to kill insects. We screened a range of environmental bacteria isolates for their abilities to kill target aphid species. Tests demonstrated the killing aptitude of these bacteria against six aphid genera (including Myzus persicae). No single bacterial strain was identified that was consistently toxic to insecticide‐resistant aphid clones than susceptible clones, suggesting resistance to chemicals is not strongly correlated with bacterial challenge. Pseudomonas fluorescens PpR24 proved the most toxic to almost all aphid clones whilst exhibiting the ability to survive for over three weeks on three plant species at populations of 5–6 log CFU cm−2 leaf. Application of PpR24 to plants immediately prior to introducing aphids onto the plants led to a 68%, 57% and 69% reduction in aphid populations, after 21 days, on Capsicum annuum, Arabidopsis thaliana and Beta vulgaris respectively. Together, these findings provide new insights into aphid susceptibility to bacterial infection with the aim of utilizing bacteria as effective biocontrol agents. [ABSTRACT FROM AUTHOR]