Leguminous Plants Research Articles

Phytopathogenic Curtobacterium flaccumfaciens Strains Circulating on Leguminous Plants, Alternative Hosts and Weeds in Russia.

Many bacterial plant pathogens have a broad host range important for their life cycle. Alternate hosts from plant families other than the main (primary) host support the survival and dissemination of the pathogen population even in absence of main host plants. Metabolic peculiarities of main and alternative host plants can affect genetic diversity within and between the pathogen populations isolated from those plants. Strains of Gram-positive bacterium Curtobacterium flaccumfaciens were identified as being causal agents of bacterial spot and wilt diseases on leguminous plants, and other crop and weed plants, collected in different regions of Russia. Their biochemical properties and susceptibility to copper compounds have been found to be relatively uniform. According to conventional PCR assays, all of the isolates studied were categorised as pathovar Curtobacterim flaccumfaciens pv. flaccumfaciens, a pathogen of legumes. However, the strains demonstrated a substantial diversity in terms of virulence on several tested host plants and different phylogenetic relationships were revealed by BOX-PCR and alanine synthase gene (alaS) sequencing.

Dietary Puerarin Supplementation Improves Immune Response and Antioxidant Capacity of Sows.

Puerarin is an isoflavone extracted from Pueraria mirifica, a wildlife leguminous plant. It has been reported to possess antioxidant, anti-inflammatory, and anti-bacterial properties. However, the effects of directly adding puerarin to the diets of sows, in terms of reproductive performance and antioxidant properties, have not been reported. For this study, 240 sows with varying parities were selected and randomly divided into six treatment groups using a two × three experimental design. The six treatment groups consisted of two diets (control and puerarin) and three parities (zero, one, and two parities or more). The puerarin group was supplemented with 1 g/kg of puerarin. The experiment commenced with mating and continued until 21 days post-delivery. The sow reproductive performance was not affected by supplementing their diets with puerarin (p > 0.05). Dietary supplementation with puerarin significantly increased the daily body weight (BW) gain of piglets and their mean BW at weaning (p < 0.05). Compared with the control group, sows in the puerarin group had significantly higher glutathione peroxidase activity in serum and also significantly increased immunoglobulin A and G levels in serum, colostrum, and milk, but significantly lower malondialdehyde concentration in serum (p < 0.05). Thus, puerarin improved the immune response and antioxidant capacity of sows and increased the daily BW gain of their offspring.

Xanthomonas fuscans subsp. fuscans — a Pathogen of Small Brown Spot of Legumes

Xanthomonas fuscans subsp. fuscans is known as an obligate phytopathogen — the pathogen of small brown spot of beans that gradually expands the range of host plants and spreads worldwide on legumes. The review provides data on the problems of the pathogen’s systematics and its change depending on the new research and improvement of methods for studying biological properties. Historical data on the first stages of isolation of X. fuscans subsp. fuscans from bean and new stages of its spread and isolation from soybean in Ukraine, after which the pathogen moved from the monophage to polyphage status within the same plant family. The importance of X. fuscans subsp. fuscans as a potentially dangerous phytopathogen, as evidenced by the presence of its samples in many collections of living microorganisms in the world and the quarantine status of the pathogen in a number of European countries are underlined. It has been shown that the phytopathogen X. fuscans subsp. fuscans does not differ significantly from other xanthomonads in terms of its cultural, morphological, physiological, and biochemical properties, especially those that cause diseases of leguminous plants. At the same time, the only but the main feature of this bacterial culture is emphasized — the increased amount and activity of the intracellular enzyme tyrosinase, which distinguishes X. fuscans from all other bacterial phytopathogens and not only among xanthomonads. The variants of the stage of synthesis of tyrosinase and melanin in bacteria, due to which the black-brown pigment is formed, and the lack of research on the pathway of tyrosinase synthesis in phytopathogenic bacteria, in particular X. fuscans subsp. fuscans, are analized. The data on genotypic properties of X. fuscans subsp. fuscans, its affinity with other pathogens of the genus Xanthomonas that cause diseases of leguminous plants, and the possible role of the phenomenon of «horizontal gene transfer» in their affinity along with differences in biological properties are considered. The analyzed literature indicates the potential danger of the causative agent of small brown spot of legumes and the need for constant monitoring of the spread and study of its biological properties to develop methods for controling the spread of X. fuscans subsp. fuscans.

First Ex Situ In Vitro Propagation Protocol of Coronilla viminalis Salisb., An Endangered Fodder Species Adapted to Drought and Salinity

Coronilla viminalis Salisb. is a fodder leguminous plant from the Canary Islands and Northwestern Africa with adaptation to drought. Its conservation status is critical. Its low germination capacity and intense loss of viability of the seeds over time complicate its conservation, limiting its long-term maintenance in germplasm banks and hampering its potential use as a resilient fodder crop. Therefore, in this work, two alternative propagation methods have been addressed. The first was based on facilitating seed germination under aseptic conditions, supplementing the media with gibberellic acid (GA3). The latter consisted of creating a micropropagation method from nodal segments and testing different media and pretreatments with indole-3-acetic acid (IAA). The quantity and quality of the roots were assessed, and the plant acclimation rate was measured. The results showed that the optimum concentration of GA3 for germination, up to 98%, was 250 PPM. The experiments showed that using IAA in the micropropagation media is critical for in vitro rooting in this species. A hormonal pretreatment with IAA significantly improved the rooting efficiency compared to supplementing it into the culture media. One hundred percent of acclimated plants survived the process. These new protocols will help conserve the species and explore its possibilities as fodder crops.

Interspecific recognition based on cuticular hydrocarbons mediates reproduction control in aphids

The preset study tested whether an aphid species can control its reproduction by recognizing the presence and density of a rival species. Acyrthosiphon pisum and Megoura crassicauda often coexist on the same leguminous plant. We established clonal colonies from each species and mixed colonies with one A. pisum and one M. crassicauda adult. There were no significant differences in the population growth patterns of the two species at 20 °C. However, mixed colonies increased faster and attained larger colony sizes than the clonal colonies. Thus, positive interspecific interactions were confirmed. A mixed colony was dominated by the members of a clone that produced a greater number of newborns in the initial stage, irrespective of the species. Thus, we confirmed the priority effect in the interspecific competition. To simulate the priority effect, 15 glass beads coated with the hexane extract of M. crassicauda aphids were attached to a cut leaf, to which one A. pisum adult was transferred. The presence of the hexane extract of M. crassicauda greatly reduced the reproductive rate of A. pisum adults. We conclude that aphids can control their reproduction by evaluating the relative density of rivals to fellow aphids based on the cuticular hydrocarbons.

Recent progress in the study of chemical constituents and pharmacological effects of Cassia Semen

Cassia Semen is the mature seed of the leguminous plant Cassia obtusifolia L. or Cassia tora L. They are known for clearing heat, improving vision, and promoting bowel movements. Modern chemical research has shown that Cassia Semen is rich in anthraquinones, naphthopyranones, and fatty acids, among other chemical components. Pharmacological studies have demonstrated various effects of Cassia Semen, including lowering blood lipid levels, reducing blood pressure, regulating blood glucose, promoting bowel movements, protecting the liver, improving vision, exhibiting antioxidant and anti-aging properties, inhibiting bacteria, and exerting anti-cancer effects. By reviewing recent domestic and international modern research on Cassia Semen, this article provides a literature review on its chemical constituents, pharmacological effects, and recent progress in clinical studies. The aim is to offer references for the rational clinical application of Cassia Semen, the mechanisms of its pharmacological and toxicological effects, as well as the modern development of traditional Chinese medicine.

Potential Use of Wild Legume Plant Exudates for the Prevention of Fusarium Wilt Disease (Fusarium oxysporum) in Chickpea (Cicer arietinum L.)

The aim of this study was to determine the potential of using wild legume exudates as a biocontrol agent against Fusarium oxysporium which causes wilt in chickpea plants. For this purpose, wild leguminous plants from Erzurum were collected and their exudates were obtained. From wild legume plants from which exudates were obtained in the study, belonging to the genus Onobrychis which It was determined that two of them are endemic and the other three are cosmopolitan species. Chickpea plant was grown in Green house and the plants were infected with F.oxysporium. Legume exudates were applied to the infected plants. The data like root stem length, were measured root stem length, chlorophyll, carotenoid, and lipid peroxidation amounts were measured. In addition, antioxidant enzymes were examined. The result of our finding concluded that exudated from wild legume has been concluded that exudates obtained from wild legume plants can be used as a non-toxic and economically viable fungicide against F.oxysporium. In addition, the results ındıcated that both endemic and cosmopolitan Onobrychis exudates can be used as fungicides against F.oxysporium in chickpea, which is a protein source in developing countries and is widely consumed in the world, and this is the first study for these species.

Isoflavonoid metabolism in leguminous plants: an update and perspectives.

Isoflavonoids constitute a well-investigated category of phenylpropanoid-derived specialized metabolites primarily found in leguminous plants. They play a crucial role in legume development and interactions with the environment. Isoflavonoids usually function as phytoalexins, acting against pathogenic microbes in nature. Additionally, they serve as signaling molecules in rhizobial symbiosis. Notably, owing to their molecular structure resembling human estrogen, they are recognized as phytoestrogens, imparting positive effects on human health. This review comprehensively outlines recent advancements in research pertaining to isoflavonoid biosynthesis, transcriptional regulation, transport, and physiological functions, with a particular emphasis on soybean plants. Additionally, we pose several questions to encourage exploration into novel contributors to isoflavonoid metabolism and their potential roles in plant-microbe interactions.

Diversity of endophytic bacteria isolated from leguminous agroforestry trees in western Kenya

Plants have diverse and vast niches colonized by endophytic microorganisms that promote the wellbeing of host plant. These microbes inhabit internal plant tissues with no signs of ill health. Bacterial endophytes from many plants have been isolated and characterized due to their beneficial roles however their diversity in leguminous plants still remain unexploited. Diversity of bacterial endophytes isolated from Sesbania sesban, Leucaena diversifolia and Calliandra calothyrsus was assessed using morphological and molecular characteristics. A total of 27 pure isolates were recovered from C. Calothyrsus, L. diversifolia and S. sesban constituting 44.4%, 33.3% and 22.2% from the leaves, stems and roots respectively. The isolates differentiated into Gram positive and negative with rods and spherical shapes. Analysis of 16S rRNA gene sequences revealed 8 closely related bacterial genera that consisted of Bacillus (33.3%), Staphylococcus (22.2%), Alcaligens (11.1%), Pantoea (11.1%), Xanthomonas,and Sphingomonas (7.4%) each. Others included Acinetobacter, and Pseudomonas at 3.7% each. Bacterial endophytes of genus bacillus were isolated from all the three plants. These results indicate the presence of high diversity of endophytic bacteria associated with the different parts of L. diversifolia, S. sesban and C. salothyrsus growing in western Kenya.

Effect of Long-Term Different Land Uses on Improving Stable Humic Compounds in Arenosol

There has not been enough research conducted on the effect of land use on the composition of humus in Arenosols. This long-term study (1995–2022) aimed to determine the differences in the formation of humic compounds in the natural and agricultural ecosystems of Arenosols. Soil samples were collected from six plots at two soil depths (0–15 and 15–25 cm), with four replicates. Conclusions were reached based on the results of the accumulation of humic substances (HSs) and their qualitative fractional composition, C/N ratio, humification degree (HD), and the optical properties of the humus substances. Afforestation, after 27 years, significantly increased (+6.7 g kg−1) the soil organic carbon (SOC) and influenced the qualitative composition of HS: HA + FA 79.3% of the SOC. Grassland cultivation showed faster (+3.8 g kg−1) SOC sequestration, a higher HA/FA ratio, and an increased HD. Arenosols may be used in crop rotation with approximately 40% leguminous plants to maintain a stable humus balance. Additionally, the effects of mineral fertilisers on the humification processes and humus quality of +2.59 g kg−1 SOC, +1.27 g kg−1 humin in crop rotation, +3.26 g kg−1 SOC, and 2.82 g kg−1 humin in a grass cultivation field were established. For SOC accumulation and a larger humus amount of a better quality, it is recommended that an Arenosol is used, as it is suitable for use in perennial cut grasslands, natural grasslands, and pine afforestation.

Urease from Vigna umbellata seeds: isolation, partial purification, characterization and antifungal activity

Urease (EC 3.5.1.5) hydrolyzes urea to produce ammonia and carbamate. Urease can be synthesized by plants, fungi and bacteria. In agriculture, urease is needed efficiently to play a major role in the urea cycle as source of plant nitrogen in the soil. Rice beans (Vigna umbellata) are leguminous plants from the Fabaceae family that contain high urease activity. This study isolated urease from the seed coat and without the seed coat of rice beans. The urease activity in rice beans without seed coat was higher than that of the activity with seed coat. The amount of ammonia produced with the addition of 1 µL of urease enzyme of rice beans without seed coat was 13 µg which was higher than the amino produced from the seed coat sample (8.8 µg). The concentration of urease enzyme from rice beans was obtained at 7.238 mg/mL. Analyses of gel electrophoresis indicated that urease from rice beans are composed of four polypeptide chains with molecular weights of about 52, 33, 22 and 10 kDa. Then rice beans urease exhibited no antifungal activity against Aspergillus niger, Aspergillus fumigatus, Microsporum canis, Fusarium oxysporum subsp. lini, Trichophyton rubrum, Candida glabrata and Candida albicans.

Molecular Characterization of an Isolate of Bean Common Mosaic Virus First Identified in Gardenia Using Metatranscriptome and Small RNA Sequencing.

Gardenia (Gardenia jasminoides) is a popular and economically vital plant known for its ornamental and medicinal properties. Despite its widespread cultivation, there has been no documentation of plant viruses on gardenia yet. In the present study, gardenia leaves exhibiting symptoms of plant viral diseases were sampled and sequenced by both metatranscriptome and small RNA sequencing. As a consequence, bean common mosaic virus (BCMV) was identified in gardenia for the first time and named BCMV-gardenia. The full genome sequence of BCMV-gardenia is 10,054 nucleotides (nt) in length (excluding the poly (A) at the 3' termini), encoding a large polyprotein of 3,222 amino acids. Sequence analysis showed that the N-termini of the polyprotein encoded by BCMV-gardenia is less conserved when compared to other BCMV isolates, whereas the C-termini is the most conserved. Maximum likelihood phylogenetic analysis showed that BCMV-gardenia was clustered closely with other BCMV isolates identified outside the leguminous plants. Our results indicated that the majority of BCMV-gardenia virus-derived small interfering RNAs (vsiRNAs) were 21 nt and 22 nt, with 21 nt being more abundant. The first nucleotide at the 5' termini of vsiRNAs derived from BCMV-gardenia preferred U and A. The ratio of vsiRNAs derived from sense (51.1%) and antisense (48.9%) strands is approaching, and the distribution of vsiRNAs along the viral genome is generally even, with some hot spots forming in local regions. Our findings could provide new insights into the diversity, evolution, and host expansion of BCMV and contribute to the prevention and treatment of this virus.

Optimization of emulsion properties of chickpea protein and its application in food

AbstractAs a leguminous plant, chickpea has been widely concerned by researchers because of its high yield, low production cost, and high protein content. Compared with soy protein, chickpea protein has lower allergenicity, better solubility, and foaming properties. Therefore, chickpea protein is considered a good alternative to animal protein. Currently, chickpea protein is used in products made from flour, such as cookies, breads, and noodles. Chickpea protein emulsion also has many potential applications in food, such as delaying lipid oxidation, transporting nutrients, and serving as a substitute for animal fat. However, the physical, chemical stability and biological activity of chickpea protein emulsion are easily affected by many factors, including salt ionic strength, pH, temperature, and so forth in food processing. In order to better apply chickpea protein emulsions to more real food substrates, it is necessary and meaningful to study the factors that affect the characteristics of the emulsion. The properties of chickpea protein emulsion can be improved by pretreatment of chickpea protein, including pH adjustment, cross‐linking by glutaminase, hydrolysis of by protein hydrolase, formation of complex with glycosides or polysaccharides and acetylation modification. In the future, the optimized and stable chickpea protein emulsion will be more widely used in the food field.

Heavy metals accumulation by Vicia faba L and Pisum sativum L plants grown in contaminated soil

This study was conducted in agricultural fields near the city of Al-Marj. Al- Marj area is located on the southern coast of the Mediterranean Sea in the province of Cyrenaica . Many vegetables and fruits grow in these agricultural fields, and the domestic and industrial wastewater streams pass through them, and the study aimed to determine the quantity of heavy metals( Cd ,Ni, and Pb) in leguminous plants beans( Vicia faba L) and peas (Pisum sativum L) growing in soil contaminated with domestic and industrial wastewater. All the experiments were conducted at the Al-Bariqa company laboratory in Tripoli, Libya. Samples of some grown vegetables, i.e.,beans( Vicia faba L ) and peas (Pisum sativum L),were collected from seven different locations in the agricultural fields. For metal analysis, only the pods of in two studied plants samples were used, Three replicates were taken from plant samples. The study results showed that pods of studied plants in different locations contained heavy metals with different concentrations within the normal levels of toxicity except cadmium .the concentration of cadmium was over then (0.1)ppm., which was applied by (WHO)

Leguminous green manure intercropping changes the soil microbial community and increases soil nutrients and key quality components of tea leaves.

Intercropping, a green and sustainable planting pattern, has demonstrated positive effects on plant growth and the soil environment. However, there is currently little research on the influence of intercropping leguminous plants and using them as green manure on the soil environment and tea quality. During the profuse flowering period of Chinese milkvetch, the contents of tea amino acids and soluble sugar in intercropping tea plants with soybean increased by 6.89 and 54.58%. Moreover, there was 27.42% increase in soil ammonium nitrogen and 21.63% increase in available nitrogen. When Chinese milkvetch was returned to soil for 1month during its profuse flowering period, the soybean and Chinese milkvetch as green manure enhanced tea amino acids and soluble sugar by 9.11 and 33.96%, and soil ammonium nitrogen, nitrate nitrogen and available nitrogen increased by 25.04, 77.84, and 48.90%. Intercropping systems also have positive effects on tea quality components, soil fertility, and soil microbial communities during the profuse flowering period of soybeans and when soybeans with this period were returned to the field for 1month. Furthermore, the soil fertility index was significantly increased, especially in the intercropping system of tea-soybean-Chinese milkvetch. The soil bacterial community complexity and fungal community interactions were significantly increased. Soil pH, nitrate nitrogen, and available phosphorus were found to be crucial influencing factors on soil microbial communities, specifically bacterial communities. These results highlight the significance of optimizing intercropping systems to improve the soil environment and tea quality components. They also provide a theoretical foundation for promoting the sustainable development of tea plantations.

Matrine reduced intestinal stem cell damage in eimeria necatrix-infected chicks via blocking hyperactivation of Wnt signaling

BackgroundCoccidiosis is a rapidly spreading and acute parasitic disease that seriously threatening the intestinal health of poultry. Matrine from leguminous plants has anthelmintic and anti-inflammatory properties. PurposeThis assay was conducted to explore the protective effects of Matrine and the AntiC (a Matrine compound) on Eimeria necatrix (EN)-infected chick small intestines and to provide a nutritional intervention strategy for EN injury. Study designThe in vivo (chick) experiment: A total of 392 one-day-old yellow-feathered broilers were randomly assigned to six groups in a 21-day study: control group, 350 mg/kg Matrine group, 500 mg/kg AntiC group, EN group, and EN + 350 mg/kg Matrine group, EN + 500 mg/kg AntiC group. The in vitro (chick intestinal organoids, IOs): The IOs were treated with PBS, Matrine, AntiC, 3 μM CHIR99021, EN (15,000 EN sporozoites), EN + Matrine, EN + AntiC, EN + Matrine + CHIR99021, EN + AntiC + CHIR99021. MethodsThe structural integrity of chicks jejunal crypt-villus axis was evaluated by hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM). And the activity of intestinal stem cells (ISCs) located in crypts was assessed by in vitro expansion advantages of a primary in IOs model. Then, the changes of Wnt/β-catenin signaling in jejunal tissues and IOs were detected by Real-Time qPCR,Western blotting and immunohistochemistry. ResultsThe results showed that dietary supplementation with Matrine or AntiC rescued the jejunal injury caused by EN, as indicated by increased villus height, reduced crypt hyperplasia, and enhanced expression of tight junction proteins. Moreover, there was less budding efficiency of the IOs expanded from jejunal crypts of chicks in the EN group than that in the Matrine and AntiC group, respectively. Further investigation showed that AntiC and Matrine inhibited EN-stimulated Wnt/β-catenin signaling. The fact that Wnt/β-catenin activation via CHIR99021 led to the failure of Matrine and AntiC to rescue damaged ISCs confirmed the dominance of this signaling. ConclusionOur results suggest that Matrine and AntiC inhibit ISC proliferation and promote ISC differentiation into absorptive cells by preventing the hyperactivation of Wnt/β-catenin signaling, thereby standardizing the function of ISC proliferation and differentiation, which provides new insights into mitigating EN injury by Matrine and AntiC.

Regulation of nitric oxide by phytoglobins in Lotus japonicus is involved in mycorrhizal symbiosis with Rhizophagus irregularis

Various reactive molecular species are generated in plant–microbe interactions, and these species participate in defense and symbiotic responses. Leguminous plants successfully establish symbiosis by maintaining an appropriate level of nitric oxide (NO), which is generated in the roots and nodules during root nodule symbiosis. Phytoglobin (plant hemoglobin) controls NO levels in plants. In this study, we investigated mycorrhizal symbiosis, which occurs in more than 80% of land plants, between Rhizophagus irregularis and Lotus japonicus to clarify the involvement of phytoglobin-mediated NO regulation. The mycorrhizae of L. japonicus exhibited higher NO levels in the presence of R. irregularis than in its absence, especially at the infection site. LjGlb1–1, a phytoglobin that regulates NO level in L. japonicus, was upregulated during symbiosis with R. irregularis. In transformed hairy roots carrying the ProLjGlb1–1:GUS construct, LjGlb1–1 expression was observed at the R. irregularis infection site. We further examined the symbiotic phenotypes of L. japonicus lines with high and low LjGlb1–1 expression with R. irregularis. During mycorrhizal symbiosis, the high LjGlb1–1 expression line exhibited better growth than the wild-type, whereas the low expression line exhibited poor growth. In addition, the expression of LjPT4, a phosphate transporter specific to mycorrhizal symbiosis, was higher in the high LjGlb1–1 expression line, whereas that of the tubulin gene of R. irregularis was lower in the low LjGlb1–1 expression line than in the wild-type. These results confirm that NO regulation by LjGlb1–1 is involved in mycorrhizal symbiosis in L. japonicus, as it is reportedly in nitrogen-fixing symbiosis.

Biological Processing of Leguminous Plants as Fish Feed Ingredients

Fish feed has a crucial role in the success of fish farming, namely influencing growth. Development and use of alternative feed in fish farming as a solution to reduce pressure on natural resources and increase the sustainability of the fisheries sector. The use of legume plants as an alternative fish feed ingredient can be used to support the sustainability of fish farming. This review article aims to collect and provide information about several research results regarding the use of legume plants as ingredients in fish feed. The method used in preparing this review article is a literature review. Many studies have been conducted to evaluate the nutritional potential, availability, and impact of the use of legume plants on fish growth. Legumes have the potential to be used as fish feed because their protein content ranges from 27-35% and have been proven to have an effect on increasing body weight due to their nutritional content so they can be used as alternative feed.

Management of grassland: A necessary tool to maintain plant and earthworm diversity

In temperate grassland, earthworms contribute to the major soil processes which determine most of the ecosystem services. The characteristics of plant communities in grassland are key factors in maintaining earthworm communities, however effects of different herbage management on earthworms remain largely unknown. In this context, the aim of the present study was to determine the long-term effects of herbage management on grassland plant and earthworm communities. Plants and earthworms were sampled in a 14-years-old experiment in upland grasslands (Massif central, France). Abandoned grasslands were compared with mowed grasslands and with pastures grazed by cattle (at low or high intensities) or grazed by sheep (at low intensity). Compared to abandoned grassland, herbage management by grazing or by mowing display higher leguminous plant, community-weighted mean Ellenberg light values as well as plant richness while they display lower percentage of plant litter and community-weighted mean Ellenberg nitrogen values. The differences in plant richness were associated with a significant change in plant community structure. Compared to the abandoned grassland, herbage management by grazing or mowing significantly display higher earthworm biomass and total richness. Except for pastures grazed by cattle at high intensity, earthworm abundance was at least twice that in the grassland at low grazing intensity or mowing compared to the abandoned grassland. Earthworm communities were significantly different between grazed and mown treatments notably due to changes within Aporrectodea anecic and endogeic earthworm species. Overall, herbage management by animals or by mechanical export is beneficial for plant and earthworm diversity although no clear differences between management practices for earthworm richness, total biomass or total abundance were observed. Our results highlight that abandonment does not preserve biodiversity (plant, soil macrofauna) while management of grassland by grazing or mowing is a necessary tool for biodiversity conservation and improvement.

Arbuscular mycorrhizal hyphae facilitate rhizobia dispersal and nodulation in legumes.

In soil ecosystems, rhizobia occupy the rhizosphere of legume roots to form nodules, a process triggered by microbial recognition of specific root-derived signals (i.e. flavonoids). However, soil conditions can limit bacterial motility, restricting signal perception to the area directly influenced by roots. Legumes, like most plants of agricultural interest, associate with arbuscular mycorrhizal fungi, whose hyphae develop extensively in the soil, potentially providing an effective dispersal network for rhizobia. We hypothesized that mycelial networks of arbuscular mycorrhizal fungi play a role in signal transmission and act as a highway, enabling rhizobia to migrate from distant soil to the roots of leguminous plants. Using in vitro and greenhouse microcosm systems, we demonstrated that Rhizophagus irregularis helps Shinorhizobium meliloti to migrate towards the legume Medicago truncatula, triggering nodulation, a mechanism absent without the arbuscular mycorrhizal fungus. Metabolomics analysis revealed eight flavonoids unique to the compartment containing extraradical hyphae of the arbuscular mycorrhizal fungus linked to M. truncatula roots, associated with Sinorhizobium meliloti growth and nod gene expression. Rhizobia plated on the extraradical hyphae connecting two plants (the legume M. truncatula and non-legume Solanum tuberosum) by a common mycelium network, showed preference for the legume, suggesting the chemoattraction by specific signals transported by the fungus connected to the legume. Simultaneously, S. meliloti stimulated the cytoplasmic/protoplasmic flow in the hyphae, likely increasing the release of nutrients and signals. Our results highlight the importance of extraradical hyphae (i.e. the mycorrhizal pathway) of arbuscular mycorrhizal fungi for the migration of rhizobia over long distances to the roots, leading to nodulation.