Plant Immunity Modulation in Arbuscular Mycorrhizal Symbiosis and Its Impact on Pathogens and Pests.

Arbuscular mycorrhizal (AM) symbiosis is the oldest and most widespread mutualistic association on Earth and involves plants and soil fungi belonging to Glomeromycotina. A complex molecular, cellular, and genetic developmental program enables partner recognition, fungal accommodation in plant tissues, and activation of symbiotic functions such as transfer of phosphorus in exchange for carbohydrates and lipids. AM fungi, as ancient obligate biotrophs, have evolved strategies to circumvent plant defense responses to guarantee an intimate and long-lasting mutualism. They are among those root-associated microorganisms able to boost plants' ability to cope with biotic stresses leading to mycorrhiza-induced resistance (MIR), which can be effective across diverse hosts and against different attackers. Here, we examine the molecular mechanisms underlying the modulation of plant immunity during colonization by AM fungi and at the onset and display of MIR against belowground and aboveground pests and pathogens. Understanding the MIR efficiency spectrum and its regulation is of great importance to optimizing the biotechnological application of these beneficial microbes for sustainable crop protection.

The imprint of microbe-induced plant resistance in plant-associated insects.

Beneficial microbes induce resistance in plants (MIR), imposing both lethal and sublethal effects on herbivorous insects. We argue that herbivores surviving MIR carry metabolic and immunological imprints of MIR with cascading effects across food webs. We propose that incorporating such cascading effects will strongly enhance the current MIR research framework.

Time to diagnosis in systemic lupus erythematosus: Associated factors and its impact on damage accrual and mortality. Data from a multi-ethnic, multinational Latin American lupus cohort.

BACKGROUND: Systemic lupus erythematosus (SLE) often mimics symptoms of other diseases, and the interval between symptom onset and diagnosis may be long in some of these patients. Aims: To describe the characteristics associated with the time to SLE diagnosis and its impact on damage accrual and mortality in patients with SLE from a Latin American inception cohort. METHODS: Patients were from a multi-ethnic, multi-national Latin-American SLE inception cohort. All participating centers had specialized lupus clinics. Socio-demographic, clinical/laboratory, disease activity, damage, and mortality between those with a longer and a shorter time to diagnosis were compared using descriptive statistical tests. Multivariable Cox regression models with damage accrual and mortality as the end points were performed, adjusting for age at SLE diagnosis, gender, ethnicity, level of education, and highest dose of prednisone for damage accrual, plus highest dose of prednisone, baseline SLEDAI, and baseline SDI for mortality. RESULTS: Of the 1437 included in these analyses, the median time to diagnosis was 6.0 months (Q1-Q3 2.4-16.2); in 721 (50.2%) the time to diagnosis was longer than 6 months. Patients whose diagnosis took longer than 6 months were more frequently female, older at diagnosis, of Mestizo ethnicity, not having medical insurance, and having "non-classic" SLE symptoms. Longer time to diagnosis had no impact on either damage accrual (HR 1.09, 95% CI 0.93-1.28, p = 0.300) or mortality (HR 1.37, 95% CI 0.88-2.12, p = 0.200). CONCLUSIONS: In this inception cohort, a maximum time of 24 months with a median of 6 months to SLE diagnosis had no apparent negative impact on disease outcomes (damage accrual and mortality).

Secretion of Interleukin 6 in Human Skeletal Muscle Cultures Depends on Ca2+ Signalling.

The systemic effects of physical activity are mediated by the release of IL-6 and other myokines from contracting muscle. Although the release of IL-6 from muscle has been extensively studied, the information on the cellular mechanisms is fragmentary and scarce, especially regarding the role of Ca2+ signals. The aim of this study was to characterize the role of the main components of Ca2+ signals in human skeletal muscle cells during IL-6 secretion stimulated by the Ca2+ mobilizing agonist ATP. Primary cultures were prepared from surgical samples, fluorescence microscopy was used to evaluate the Ca2+ signals and the stimulated release of IL-6 into the medium was determined using ELISA. Intracellular calcium chelator Bapta, low extracellular calcium and the Ca2+ channels blocker La3+ reduced the ATP-stimulated, but not the basal secretion. Secretion was inhibited by blockers of L-type (nifedipine, verapamil), T-type (NNC55-0396) and Orai1 (Synta66) Ca2+ channels and by silencing Orai1 expression. The same effect was achieved with inhibitors of ryanodine receptors (ryanodine, dantrolene) and IP3 receptors (xestospongin C, 2-APB, caffeine). Inhibitors of calmodulin (calmidazolium) and calcineurin (FK506) also decreased secretion. IL-6 transcription in response to ATP was not affected by Bapta or by the T channel blocker. Our results prove that ATP-stimulated IL-6 secretion is mediated at the post-transcriptional level by Ca2+ signals, including the mobilization of calcium stores, the activation of store-operated Ca2+ entry, and the subsequent activation of voltage-operated Ca2+ channels and calmodulin/calcineurin pathways.

Carbohydrate and lipid balances in the positive plant phenotypic response to arbuscular mycorrhiza: increase in sink strength.

The exchange of phosphorus (P) and carbon (C) between plants and arbuscular mycorrhizal fungi (AMF) is a major determinant of their mutualistic symbiosis. We explored the C dynamics in tomato (Solanum lycorpersicum) inoculated or not with Rhizophagus irregularis to study their growth response under different NaH2 PO4 concentrations (Null P, 0 mM; Low P, 0.065 mM; High P, 1.3 mM). The percentage of AMF colonization was similar in plants under Null and Low P, but severely reduced under High P. However, the AMF mass biomarker 16:1ω5 revealed higher fungal accumulation in inoculated roots under Low P, while more AMF spores were produced in the Null P. Under High P, AMF biomass and spores were strongly reduced. Plant growth response to mycorrhiza was negative under Null P, showing reduction in height, biovolume index, and source leaf (SL) area. Under Low P, inoculated plants showed a positive response (e.g., increased SL area), while inoculated plants under High P were similar to non-inoculated plants. AMF promoted the accumulation of soluble sugars in the SL under all fertilization levels, whereas the soluble sugar level decreased in roots under Low P in inoculated plants. Transcriptional upregulation of SlLIN6 and SlSUS1, genes related to carbohydrate metabolism, was observed in inoculated roots under Null P and Low P, respectively. We conclude that P-limiting conditions that increase AMF colonization stimulate plant growth due to an increase in the source and sink strength. Our results suggest that C partitioning and allocation to different catabolic pathways in the host are influenced by AMF performance.

Compatibility of mycorrhiza-induced resistance with viral and bacterial entomopathogens in the control of Spodoptera exigua in tomato.

BACKGROUND: Arbuscular mycorrhizal fungi (AMF) are soil-borne microorganisms that establish mutualistic associations with roots of most terrestrial plants. This symbiosis results in nutritional and defensive benefits to the host plant, usually conferring protection against biotic stresses, but its indirect impact on third trophic levels is still unknown. In the present work, we explore whether the symbiosis of tomato plants with Funneliformis mosseae (and/or exposition to herbivory) influences the interaction of the generalist pest Spodoptera exigua (Lepidoptera: Noctuidae) with bacterial (Bacillus thuringiensis) and viral (baculovirus, SeMNPV) natural entomopathogens. RESULTS: Symbiosis with AMF and previous herbivory reduces the relative growth of S. exigua, increases its susceptibility to a sublethal dose of B. thuringiensis and has positive or neutral impact on the lethality of SeMNPV. Reduction of the phenoloxidase activity, a marker of the insect immune response, was associated with the larval feeding on plant material previously exposed to herbivory but not to the AMF. In addition, no changes in the insect gut microbiota could be associated with the observed changes in larval growth and susceptibility to the entomopathogens. CONCLUSION: Our findings provide the first evidence of compatibility of AMF symbiosis in tomato with the use of bacterial and viral entomopathogens, contributing to the development of novel approaches to combine the beneficial effect of AMF and entomopathogens in biological pest control. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phosphorus availability drives mycorrhiza induced resistance in tomato.

Arbuscular mycorrhizal (AM) symbiosis can provide multiple benefits to the host plant, including improved nutrition and protection against biotic stress. Mycorrhiza induced resistance (MIR) against pathogens and insect herbivores has been reported in different plant systems, but nutrient availability may influence the outcome of the interaction. Phosphorus (P) is a key nutrient for plants and insects, but also a regulatory factor for AM establishment and functioning. However, little is known about how AM symbiosis and P interact to regulate plant resistance to pests. Here, using the tomato-Funneliformis mosseae mycorrhizal system, we analyzed the effect of moderate differences in P fertilization on plant and pest performance, and on MIR against biotic stressors including the fungal pathogen Botrytis cinerea and the insect herbivore Spodoperta exigua. P fertilization impacted plant nutritional value, plant defenses, disease development and caterpillar survival, but these effects were modulated by the mycorrhizal status of the plant. Enhanced resistance of F. mosseae-inoculated plants against B. cinerea and S. exigua depended on P availability, as no protection was observed under the most P-limiting conditions. MIR was not directly explained by changes in the plant nutritional status nor to basal differences in defense-related phytohormones. Analysis of early plant defense responses to the damage associated molecules oligogalacturonides showed primed transcriptional activation of plant defenses occurring at intermediate P levels, but not under severe P limitation. The results show that P influences mycorrhizal priming of plant defenses and the resulting induced-resistance is dependent on P availability, and suggest that mycorrhiza fine-tunes the plant growth vs defense prioritization depending on P availability. Our results highlight how MIR is context dependent, thus unravel molecular mechanism based on plant defence in will contribute to improve the efficacy of mycorrhizal inoculants in crop protection.

Flavonoids promote Rhizophagus irregularis spore germination and tomato root colonization: A target for sustainable agriculture.

The use of arbuscular mycorrhizal (AM) fungi has great potential, being used as biostimulants, biofertilizers and bioprotection agents in agricultural and natural ecosystems. However, the application of AM fungal inoculants is still challenging due to the variability of results when applied in production systems. This variability is partly due to differences in symbiosis establishment. Reducing such variability and promoting symbiosis establishment is essential to improve the efficiency of the inoculants. In addition to strigolactones, flavonoids have been proposed to participate in the pre-symbiotic plant-AM fungus communication in the rhizosphere, although their role is still unclear. Here, we studied the specific function of flavonoids as signaling molecules in AM symbiosis. For that, both in vitro and in planta approaches were used to test the stimulatory effect of an array of different subclasses of flavonoids on Rhizophagus irregularis spore germination and symbiosis establishment, using physiological doses of the compounds. We show that the flavone chrysin and the flavonols quercetin and rutin were able to promote spore germination and root colonization at low doses, confirming their role as pre-symbiotic signaling molecules in AM symbiosis. The results pave the way to use these flavonoids in the formulation of AM fungal-based products to promote the symbiosis. This can improve the efficiency of commercial inoculants, and therefore, help to implement their use in sustainable agriculture.

Nitric oxide signalling in roots is required for MYB72-dependent systemic resistance induced by Trichoderma volatile compounds in Arabidopsis.

Volatile compounds (VCs) of Trichoderma fungi trigger induced systemic resistance (ISR) in Arabidopsis that is effective against a broad spectrum of pathogens. The root-specific transcription factor MYB72 is an early regulator of ISR and also controls the activation of iron-deficiency responses. Nitric oxide (NO) is involved in the regulation of MYB72-dependent iron-deficiency responses in Arabidopsis roots, but the role of NO in the regulation of MYB72 and ISR by Trichoderma VCs remains unexplored. Using in vitro bioassays, we applied Trichoderma VCs to Arabidopsis seedlings. Plant perception of Trichoderma VCs triggered a burst of NO in Arabidopsis roots. By suppressing this burst using an NO scavenger, we show the involvement of NO in Trichoderma VCs-mediated regulation of MYB72 expression. Using an NO scavenger and the Arabidopsis lines myb72 and nia1nia2 in in planta bioassays, we demonstrate that NO signalling is required in the roots for activation of Trichoderma VCs-mediated ISR against the leaf pathogen Botrytis cinerea. Analysis of the defence-related genes PR1 and PDF1.2 points to the involvement of root NO in priming leaves for enhanced defence. Our results support a key role of root NO signalling in the regulation of MYB72 expression during the activation of ISR by Trichoderma VCs.

Strigolactones: New players in the nitrogen-phosphorus signalling interplay.

Nitrogen (N) and phosphorus (P) are among the most important macronutrients for plant growth and development, and the most widely used as fertilizers. Understanding how plants sense and respond to N and P deficiency is essential to optimize and reduce the use of chemical fertilizers. Strigolactones (SLs) are phytohormones acting as modulators and sensors of plant responses to P deficiency. In the present work, we assess the potential role of SLs in N starvation and in the N-P signalling interplay. Physiological, transcriptional and metabolic responses were analysed in wild-type and SL-deficient tomato plants grown under different P and N regimes, and in plants treated with a short-term pulse of the synthetic SL analogue 2'-epi-GR24. The results evidence that plants prioritize N over P status by affecting SL biosynthesis. We also show that SLs modulate the expression of key regulatory genes of phosphate and nitrate signalling pathways, including the N-P integrators PHO2 and NIGT1/HHO. The results support a key role for SLs as sensors during early plant responses to both N and phosphate starvation and mediating the N-P signalling interplay, indicating that SLs are involved in more physiological processes than so far proposed.

Microbial Consortia for Effective Biocontrol of Root and Foliar Diseases in Tomato.

The use of beneficial microorganisms for the biological control of plant diseases and pests has emerged as a viable alternative to chemical pesticides in agriculture. Traditionally, microbe-based biocontrol strategies for crop protection relied on the application of single microorganisms. However, the design of microbial consortia for improving the reliability of current biological control practices is now a major trend in biotechnology, and it is already being exploited commercially in the context of sustainable agriculture. In the present study, exploiting the microbial library of the biocontrol company Koppert Biological Systems, we designed microbial consortia composed of carefully selected, well-characterized beneficial bacteria and fungi displaying diverse biocontrol modes of action. We compared their ability to control shoot and root pathogens when applied separately or in combination as microbial consortia, and across different application strategies that imply direct microbial antagonism or induced systemic plant resistance. We hypothesized that consortia will be more versatile than the single strains, displaying an extended functionality, as they will be able to control a wider range of plant diseases through diverse mechanisms and application methods. Our results confirmed our hypothesis, revealing that while different individual microorganisms were the most effective in controlling the root pathogen Fusarium oxysporum or the foliar pathogen Botrytis cinerea in tomato, the consortia showed an extended functionality, effectively controlling both pathogens under any of the application schemes, always reaching the same protection levels as the best performing single strains. Our findings illustrate the potential of microbial consortia, composed of carefully selected and compatible beneficial microorganisms, including bacteria and fungi, for the development of stable and versatile biological control products for plant protection against a wider range of diseases.

Prevalence of Neural Autoantibodies in Paired Serum and Cerebrospinal Fluid in Adult Patients with Drug-Resistant Temporal Lobe Epilepsy of Unknown Etiology.

In order to determine the prevalence of neural autoantibodies in adult patients with drug-resistant temporal lobe epilepsy (DRTLE) of unknown etiology, we compared the characteristics of patients with and without autoantibodies and applied antibody predictive scores to the patients. Patients aged ≥18 years with DRTLE of unknown etiology and ≥12 months of evolution were prospectively recruited. Neural autoantibodies in serum and CSF were systematically determined in all patients. We created the ARTE (antibody in drug-resistant temporal lobe epilepsy) score based on the variables associated with the presence of neural autoantibodies. Twenty-seven patients were included. The mean (SD) age in years at the index date was 52 (±14.2) and at epilepsy onset was 32 (±17.1). The mean epilepsy duration was 19 (±12.5) years. Neural autoantibodies were detected in 51.85% (14/27) of patients. The presence of bitemporal, independent, interictal epileptiform discharges (BIIED) had a higher frequency in patients with neural autoantibodies (57.1% vs. 15.4%; p = 0.025) as well as those patients with a previous history of status epilepticus (49.2% vs. 0.0%; p = 0.007). The ARTE score showed an area under the curve (AUC) of 0.854. Using a cut-off point of ≥1, the sensitivity was 100% and the specificity was 46.1%, whereas when using a cut-off point of ≥3, the results were 35.7% and 100%, respectively. We found a high prevalence of neural autoantibodies in patients with DRTLE of unknown etiology, indicating an autoimmune mechanism. The presence of BIIED and a history of SE in DRTLE of unknown etiology are possible markers for autoimmune-associated epilepsy. The proposed ARTE score requires future validation in larger independent cohorts.

Tomato Domestication Affects Potential Functional Molecular Pathways of Root-Associated Soil Bacteria.

While it has been well evidenced that plant domestication affects the structure of the root-associated microbiome, there is a poor understanding of how domestication-mediated differences between rhizosphere microorganisms functionally affect microbial ecosystem services. In this study, we explore how domestication influenced functional assembly patterns of bacterial communities in the root-associated soil of 27 tomato accessions through a transect of evolution, from plant ancestors to landraces to modern cultivars. Based on molecular analysis, functional profiles were predicted and co-occurrence networks were constructed based on the identification of co-presences of functional units in the tomato root-associated microbiome. The results revealed differences in eight metabolic pathway categories and highlighted the influence of the host genotype on the potential functions of soil bacterial communities. In general, wild tomatoes differed from modern cultivars and tomato landraces which showed similar values, although all ancestral functional characteristics have been conserved across time. We also found that certain functional groups tended to be more evolutionarily conserved in bacterial communities associated with tomato landraces than those of modern varieties. We hypothesize that the capacity of soil bacteria to provide ecosystem services is affected by agronomic practices linked to the domestication process, particularly those related to the preservation of soil organic matter.

Mycorrhiza-Induced Resistance against Foliar Pathogens Is Uncoupled of Nutritional Effects under Different Light Intensities.

The use of microbial inoculants, particularly arbuscular mycorrhizal fungi, has great potential for sustainable crop management, which aims to reduce the use of chemical fertilizers and pesticides. However, one of the major challenges of their use in agriculture is the variability of the inoculation effects in the field, partly because of the varying environmental conditions. Light intensity and quality affect plant growth and defense, but little is known about their impacts on the benefits of mycorrhizal symbioses. We tested the effects of five different light intensities on plant nutrition and resistance to the necrotrophic foliar pathogen Botrytis cinerea in mycorrhizal and non-mycorrhizal lettuce plants. Our results evidence that mycorrhiza establishment is strongly influenced by light intensity, both regarding the extension of root colonization and the abundance of fungal vesicles within the roots. Light intensity also had significant effects on plant growth, nutrient content, and resistance to the pathogen. The effect of the mycorrhizal symbiosis on plant growth and nutrient content depended on the light intensity, and mycorrhiza efficiently reduced disease incidence and severity under all light intensities. Thus, mycorrhiza-induced resistance can be uncoupled from mycorrhizal effects on plant nutrition. Therefore, mycorrhizal symbioses can be beneficial by providing biotic stress protection even in the absence of nutritional or growth benefits.

Untapping the potential of plant mycobiomes for applications in agriculture.

Plant-fungal interactions are widespread in nature, and their multiple benefits for plant growth and health have been amply demonstrated. Endophytic and epiphytic fungi can significantly increase plant resilience, improving plant nutrition, stress tolerance and defence. Although some of these interactions have been known for decades, the relevance of the plant mycobiome within the plant microbiome has been largely underestimated. Our limited knowledge of fungal biology and their interactions with plants in the broader phytobiome context has hampered the development of optimal biotechnological applications in agrosystems and natural ecosystems. Exciting recent technical and knowledge advances in the context of molecular and systems biology open a plethora of opportunities for developing this field of research.

Mycorrhizal symbiosis primes the accumulation of antiherbivore compounds and enhances herbivore mortality in tomato.

Plant association with arbuscular mycorrhizal fungi (AMF) can increase their ability to overcome multiple stresses, but their impact on plant interactions with herbivorous insects is controversial. Here we show higher mortality of the leaf-chewer Spodoptera exigua when fed on tomato plants colonized by the AMF Funneliformis mosseae, evidencing mycorrhiza-induced resistance. In search of the underlying mechanisms, an untargeted metabolomic analysis through ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS) was performed. The results showed that mycorrhizal symbiosis had a very limited impact on the leaf metabolome in the absence of stress, but significantly modulated the response to herbivory in the damaged area. A cluster of over accumulated metabolites was identified in those leaflets damaged by S. exigua feeding in mycorrhizal plants, while unwounded distal leaflets responded similar to those from non-mycorrhizal plants. These primed-compounds were mostly related to alkaloids, fatty acid derivatives and phenylpropanoid-polyamine conjugates. The deleterious effect on larval survival of some of these compounds, including the alkaloid physostigmine, the fatty acid derivatives 4-oxododecanedioic acid and azelaic acid, was confirmed. Thus, our results evidence the impact of AMF on metabolic reprograming upon herbivory that leads to a primed accumulation of defensive compounds.

The Induced Resistance Lexicon: Do's and Don'ts.

To be protected from biological threats, plants have evolved an immune system comprising constitutive and inducible defenses. For example, upon perception of certain stimuli, plants can develop a conditioned state of enhanced defensive capacity against upcoming pathogens and pests, resulting in a phenotype called 'induced resistance' (IR). To tackle the confusing lexicon currently used in the IR field, we propose a widely applicable code of practice concerning the terminology and description of IR phenotypes using two main phenotypical aspects: local versus systemic resistance, and direct versus primed defense responses. Our general framework aims to improve uniformity and consistency in future scientific communication, which should help to avoid further misinterpretations and facilitate the accessibility and impact of this research field.

Monochloramine effects on gallbladder contractility.

Digestive inflammatory processes induce motility alterations associated with an increase in reactive oxygen species production, including monochloramine (NH2 Cl). The aim of the study was to characterize the effects of the naturally occurring oxidant monochloramine in the guinea pig gallbladder. We used standard in vitro contractility technique to record guinea pig gallbladder strips contractions. NH2 Cl caused a concentration-dependent contraction which was reduced by inhibition of extracellular Ca2+ influx and tyrosine kinase pathways. The PKC antagonist GF109203X also reduced the response but not after previous tyrosine kinase inhibition, suggesting that PKC is activated by tyrosine kinase activity. The NH2 Cl contractile effect was also reduced by inhibitors of mitogen-activated protein kinase (MAPK), nitric oxide synthase, phospholipase A2 and cyclooxygenase. In addition, NH2 Cl impaired the responses to CCK, tissue depolarization and electrical field stimulation. In conclusion, we present new evidence that monochloramine impairs not only the gallbladder response to CCK but also to membrane depolarization and nervous plexus stimulation, and that tyrosine kinase, PKC, MAPK and NO pathways are involved in the contractile direct effect of monochloramine.

An Updated Review on the Modulation of Carbon Partitioning and Allocation in Arbuscular Mycorrhizal Plants.

Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs that supply mineral nutrients to the host plant in exchange for carbon derived from photosynthesis. Sucrose is the end-product of photosynthesis and the main compound used by plants to translocate photosynthates to non-photosynthetic tissues. AMF alter carbon distribution in plants by modifying the expression and activity of key enzymes of sucrose biosynthesis, transport, and/or catabolism. Since sucrose is essential for the maintenance of all metabolic and physiological processes, the modifications addressed by AMF can significantly affect plant development and stress responses. AMF also modulate plant lipid biosynthesis to acquire storage reserves, generate biomass, and fulfill its life cycle. In this review we address the most relevant aspects of the influence of AMF on sucrose and lipid metabolism in plants, including its effects on sucrose biosynthesis both in photosynthetic and heterotrophic tissues, and the influence of sucrose on lipid biosynthesis in the context of the symbiosis. We present a hypothetical model of carbon partitioning between plants and AMF in which the coordinated action of sucrose biosynthesis, transport, and catabolism plays a role in the generation of hexose gradients to supply carbon to AMF, and to control the amount of carbon assigned to the fungus.

Resistance and Not Plant Fruit Traits Determine Root-Associated Bacterial Community Composition along a Domestication Gradient in Tomato.

Soil bacterial communities are involved in multiple ecosystem services, key in determining plant productivity. Crop domestication and intensive agricultural practices often disrupt species interactions with unknown consequences for rhizosphere microbiomes. This study evaluates whether variation in plant traits along a domestication gradient determines the composition of root-associated bacterial communities; and whether these changes are related to targeted plant traits (e.g., fruit traits) or are side effects of less-often-targeted traits (e.g., resistance) during crop breeding. For this purpose, 18 tomato varieties (wild and modern species) differing in fruit and resistance traits were grown in a field experiment, and their root-associated bacterial communities were characterised. Root-associated bacterial community composition was influenced by plant resistance traits and genotype relatedness. When only considering domesticated tomatoes, the effect of resistance on bacterial OTU composition increases, while the effect due to phylogenetic relatedness decreases. Furthermore, bacterial diversity positively correlated with plant resistance traits. These results suggest that resistance traits not selected during domestication are related to the capacity of tomato varieties to associate with different bacterial groups. Taken together, these results evidence the relationship between plant traits and bacterial communities, pointing out the potential of breeding to affect plant microbiomes.