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

Abstract

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.

Isolation and Characterization of Culturable Osmotolerant Microbiota in Hypersaline and Hypergypsic Soils as New Treatment for Osmotic Stress in Plants

“…Geologic context, soil type, and soil variables (pH, electro-conductivity) are determined as factors conditioning the microbiota. The production of 1-aminocyclopropane-1-carboxylate deaminase (ACCd) was evaluated by following the previously adapted methodology [60]. Briefly, using a 96-well plate, the strains grew in M9 medium (Merck) amended with 3 mM of ACC, and after 24 h at 28 • C and 150 rpm, the culture was measured at 600 nm in order to evaluate the culture growth and compare among the collection of strains.…”

“…We selected species with different tolerance levels of M. sativa (sensitive) and M. polymorpha (mid-tolerant) as model plants. Seeds were commercially available (Cantueso Natural Seeds, Córdoba, Spain) or were collected from nature in different regions of Portugal and Spain during spring/summer 2022 [60].…”

Combined Use of a Bacterial Consortium and Early-Colonizing Plants as a Treatment for Soil Recovery after Fire: A Model Based on Los Guájares (Granada, Spain) Wildfire

“…Additionally, we evaluated the germination rate (%) for B. bituminosa under each condition. As a reference, we evaluated the germination rate in vitro by using Magenta boxes and wet paper [ 47 ]. Here we treated the seeds with each candidate strain, as well as with the whole consortium, using a set of seeds treated just with water as control.…”

“…For this, after surface-sterilizing the seeds (incubation in 70% ethanol for 5 min, followed by three washes with double distilled water), they were incubated for 6 h in a 10 8 CFUs/mL solution. Finally, for plants germinating in the microcosm, we also evaluated the degree of development (height and biomass in dry weight) and root architecture (length and number of secondary roots), as indicated in Niza and collaborators [ 47 ].…”

“…case, could be the most interesting because the nitrogen fixation in their roots can accelerate the re-colonization of more demanding plant species, thereby reducing recovery times [ 45 , 46 ]. This strategy may make a lot of sense in the Mediterranean regions, since many of the legumes in these regions are also resistant to intense drought and high-temperature stress conditions [ 46 , 47 ]. In this present study, we analyzed the early response patterns in the “Los Guájares” wildfire as a good model for Mediterranean ecosystems.…”