Understanding Plant Social Networking System: Avoiding Deleterious Microbiota but Calling Beneficials.

Plant association with microorganisms elicits dramatic effects on the local phytobiome and often causes systemic and transgenerational modulation on plant immunity against insect pests and microbial pathogens. Previously, we introduced the concept of the plant social networking system (pSNS) to highlight the active involvement of plants in the recruitment of potentially beneficial microbiota upon exposure to insects and pathogens. Microbial association stimulates the physiological responses of plants and induces the development of their immune mechanisms while interacting with multiple enemies. Thus, beneficial microbes serve as important mediators of interactions among multiple members of the multitrophic, microscopic and macroscopic communities. In this review, we classify the steps of pSNS such as elicitation, signaling, secreting root exudates, and plant protection; summarize, with evidence, how plants and beneficial microbes communicate with each other; and also discuss how the molecular mechanisms underlying this communication are induced in plants exposed to natural enemies. Collectively, the pSNS modulates robustness of plant physiology and immunity and promotes survival potential by helping plants to overcome the environmental and biological challenges.

Intercropping Walnut and Tea: Effects on Soil Nutrients, Enzyme Activity, and Microbial Communities.

The practice of intercropping, which involves growing more than one crop simultaneously during the same growing season, is becoming more important for increasing soil quality, land-use efficiency, and subsequently crop productivity. The present study examined changes in soil physicochemical properties, enzymatic activity, and microbial community composition when walnut (Juglans spp.) was intercropped with tea (Camellia sinensis L.) plants in a forest and compared with a walnut and tea monocropping system. The results showed that walnut-tea intercropping improved the soil nutrient profile and enzymatic activity. The soil available nitrogen (AN), available phosphorus (AP), available potassium (AK), organic matter (OM) content, and sucrase activity were significantly boosted in intercropped walnut and tea than in monocropping forests. The interaction between crops further increased bacterial and fungal diversity when compared to monoculture tea forests. Proteobacteria, Bacteroidetes, Firmicutes, Chlamydiae, Rozellomycota, and Zoopagomycota were found in greater abundance in an intercropping pattern than in monoculture walnut and tea forest plantations. The walnut-tea intercropping system also markedly impacted the abundance of several bacterial and fungal operational taxonomic units (OTUs), which were previously shown to support nutrient cycling, prevent diseases, and ameliorate abiotic stress. The results of this study suggest that intercropping walnut with tea increased host fitness and growth by positively influencing soil microbial populations.

Geographically Disperse, Culturable Seed-Associated Microbiota in Forage Plants of Alfalfa (Medicago sativa L.) and Pitch Clover (Bituminaria bituminosa L.): Characterization of Beneficial Inherited Strains as Plant Stress-Tolerance Enhancers.

Agricultural production is being affected by increasingly harsh conditions caused by climate change. The vast majority of crops suffer growth and yield declines due to a lack of water or intense heat. Hence, commercial legume crops suffer intense losses of production (20-80%). This situation is even more noticeable in plants used as fodder for animals, such as alfalfa and pitch trefoil, since their productivity is linked not only to the number of seeds produced, but also to the vegetative growth of the plant itself. Thus, we decided to study the microbiota associated with their seeds in different locations on the Iberian Peninsula, with the aim of identifying culturable bacteria strains that have adapted to harsh environments and that can be used as biotreatments to improve plant growth and resistance to stress. As potentially inherited microbiota, they may also represent a treatment with medium- and long-term adaptative effects. Hence, isolated strains showed no clear relationship with their geographical sampling location, but had about 50% internal similarity with their model plants. Moreover, out of the 51 strains isolated, about 80% were capable of producing biofilms; around 50% produced mid/high concentrations of auxins and grew notably in ACC medium; only 15% were characterized as xerotolerant, while more than 75% were able to sporulate; and finally, 65% produced siderophores and more than 40% produced compounds to solubilize phosphates. Thus, Paenibacillus amylolyticus BB B2-A, Paenibacillus xylanexedens MS M1-C, Paenibacillus pabuli BB Oeiras A, Stenotrophomonas maltophilia MS M1-B and Enterobacter hormaechei BB B2-C strains were tested as plant bioinoculants in lentil plants (Lens culinaris Medik.), showing promising results as future treatments to improve plant growth under stressful conditions.