Host Plant Performance Research Articles

Diversity and interactions of rhizobacteria determine multinutrient traits in tomato host plants under nitrogen and water disturbances

Abstract Coevolution within the plant holobiont extends the capacity of host plants for nutrient acquisition and stress resistance. However, the role of the rhizospheric microbiota in maintaining multinutrient utilization (i.e., multinutrient traits) in the host remains to be elucidated. Multinutrient cycling index (MNC), analogous to the widely used multifunctionality index, provides a straightforward and interpretable measure of the multinutrient traits in host plants. Using tomato as a model plant, we characterized MNC (based on multiple aboveground nutrient contents) in host plants under different nitrogen and water supply regimes and explored the associations between rhizospheric bacterial community assemblages and host-plant multinutrient profiles. Rhizosphere bacterial community diversity, quantitative abundance, predicted function, and key topological features of the co-occurrence network were more sensitive to water supply than to nitrogen supply. A core bacteriome comprising 61 genera, such as Candidatus Koribacter and Streptomyces, persisted across different habitats and served as a key predictor of host-plant nutrient uptake. The MNC index increased with greater diversity and higher core taxon abundance in the rhizobacterial community, while decreasing with higher average degree and graph density of rhizobacterial co-occurrence network. Multinutrient absorption by host plants was primarily regulated by community diversity and rhizobacterial network complexity under the interaction of nitrogen and water. The high biodiversity and complex species interactions of the rhizospheric bacteriome play crucial roles in host-plant performance. This study supports the development of rhizosphere microbiome engineering, facilitating effective manipulation of the microbiome for enhanced plant benefits, which supports sustainable agricultural practices and plant health.

Population comparison of innate and plastic host plant preference and performance in a polyphagous insect

Population comparison of innate and plastic host plant preference and performance in a polyphagous insect

Reduced seed viability in exchange for transgenerational plant protection: Does the defensive mutualism concept pass the fitness test?

Epichloë endophytes are vertically transmitted via grass seeds and chemically defend their hosts against herbivory. Endophyte-conferred plant defence via alkaloid biosynthesis may occur independently of costs for host plant growth. However, fitness consequences of endophyte-conferred defence and transgenerational effects on herbivore resistance of progeny plants, are rarely studied. The aim of this study was to test whether severe defoliation in mother plants affects their seed production, seed germination rate, and the endophyte-conferred resistance of progeny plants. In a field study, we tested the effects of defoliation and endophyte symbiosis (Epichloë uncinata) on host plant (Festuca pratensis) performance, loline alkaloid concentrations in leaves and seeds, seed biomass and seed germination rates. In a subsequent greenhouse study, we challenged the progeny of the plants from the field study to aphid herbivory and tested whether defoliation of mother plants affects endophyte-conferred resistance against aphids in progeny plants. Defoliation of the mother plants resulted in a reduction of alkaloid concentrations in leaves and elevated the alkaloid concentrations in seeds when compared with non-defoliated endophyte-symbiotic plants. Viability and germination rate of seeds of defoliated endophyte-symbiotic plants were significantly lower compared to those of non-defoliated endophyte-symbiotic plants and endophyte-free (defoliated and non-defoliated) plants. During six weeks growth, seedlings of defoliated endophyte-symbiotic mother plants had elevated alkaloid concentrations, which negatively correlated with aphid performance. Endophyte-conferred investment in higher alkaloid levels in seeds -elicited by defoliation- provided herbivore protection in progenies during the first weeks of plant establishment. Better protection of seeds via high alkaloid concentrations negatively correlated with seed germination indicating trade-off between protection and viability.

Arbuscular mycorrhizal diversity increases across a plant productivity gradient driven by soil nitrogen availability.

Arbuscular mycorrhizal fungi (AMF) are widespread obligate symbionts of plants. This dynamic symbiosis plays a large role in successful plant performance, given that AMF help to ameliorate plant responses to abiotic and biotic stressors. Although the importance of this symbiosis is clear, less is known about what may be driving this symbiosis, the plant's need for nutrients or the excess of plant photosynthate being transferred to the AMF, information critical to assess the functionality of this relationship. Characterizing the AMF community along a natural plant productivity gradient is a first step in understanding how this symbiosis may vary across the landscape. We surveyed the AMF community diversity at 12 sites along a plant productivity gradient driven by soil nitrogen availability. We found that AMF diversity in soil environmental DNA significantly increased along with the growth of the host plants Acer rubrum and A. saccharum., a widespread tree genus. These increases also coincided with a natural soil inorganic N availability gradient. We hypothesize photosynthate from the increased tree growth is being allocated to the belowground AMF community, leading to an increase in diversity. These findings contribute to understanding this complex symbiosis through the lens of AMF turnover and suggest that a more diverse AMF community is associated with increased host-plant performance.

Tolerance Mitigates Gall Effects When Susceptible Plants Fail to Elicit Induced Defense.

Variations in plant genotypes and phenotypes are expressed in ways that lead to the development of defensive abilities against herbivory. Induced defenses are mechanisms that affect herbivore insect preferences and performance. We evaluated the performance of resistant and susceptible phenotypes of Bauhinia brevipes (Fabaceae) against attacks by the gall-inducing insect Schizomyia macrocapillata (Diptera). We hypothesized that there is a positive relationship between resistance to S. macrocapillata and host plant performance because resistance can have a high adaptive value. We evaluated plant architecture, nutritional leaf quality, leaf fluctuating asymmetry, and reproductive capacity between phenotypes. Plant performance was evaluated at three ontogenetic stages: seed, seedling, and juvenile. Overall, there were no differences in vegetative and reproductive performance or asymmetry between the resistant and susceptible mature plants. We found no relationship between leaf nutritional quality and resistance to S. macrocapillata. Plant performance was consistent across ontogeny for both phenotypes, except for five variables. Contrary to our expectations, the susceptible plants performed equally well or better than the resistant plants, suggesting that tolerance and overcompensation to herbivory in B. brevipes may be mediated by induced defense. Our study highlights the importance of multiple layers of plant defense against herbivory, where plant tolerance acts as a secondary barrier in plants susceptible to gall-inducing insects.

Macronutrient application rescues performance of tolerant sorghum genotypes when infected by the parasitic plant striga.

Infection by the hemi-parasitic plant Striga hermonthica causes severe host-plant damage and seed production losses. Increased availability of essential plant nutrients reduces infection. Whether, how and to what extent, it also reduces striga-induced host-plant damage is not well studied. Effects of improved macro- and micronutrient supply on host-plant performance under striga-free and infected conditions were investigated in greenhouse pot assays. One striga-sensitive and two striga-tolerant genotypes were compared. Plants growing in impoverished soils were supplied with (1) 25% of optimal macro- and micronutrients quantities, (2) 25% macro- and 100% micronutrients, (3) 100% macro- and 25% micronutrients, or (4) 100% of macro- and micronutrients. Photosynthesis rates of striga-infected plants of the sensitive genotype increased with improved nutrition (12.2 to 22.1 µmol/m2/s1) but remained below striga-free levels (34.9-38.8 µmol/m2/s1). For the tolerant genotypes, increased macro-nutrient supply offset striga-induced photosynthesis losses. Striga-induced relative grain losses of 100% for the sensitive genotype were reduced to 74% by increased macronutrients. Grain losses of 80% in tolerant Ochuti, incurred at low nutrient supply, were reduced to 5% by improved nutrient supply. Increasing macro-nutrient supply reduces striga impact on host-plants but can only restore losses when applied to genotypes with a tolerant background.

Fostering Growth in Cinnamomum kanehirae Cuttings: The Beneficial Role of Dark Septate Endophytes in Forest Nursery Management

Root development is critical to successful establishment after seedlings are out-planted on a forest restoration site. However, the restoration of an endangered Cinnamomum kanehirae using cuttings was limited by the lack of axial roots. Dark septate endophytes (DSEs) are an important group of asexual filamentous ascomycetous fungi and could promote the performance of host plants. In the current study, we explored the effects of four DSE strains (Melnikomyces sp., Acrocalymma vagum, Wiesneriomyces sp., and Tricholomataceae sp.) on the growth of C. kanehirae cuttings under nursery conditions. The results show that four DSE isolates are able to form symbiotic relationships with C. kanehira, enhancing the seedling height, fresh weight, and chlorophyll concentrations. Notably, the Melnikomyces sp. (DB5) showed significant improvements, secreting peroxidase and indole acetic acid. To facilitate the detection of DB5 within the host roots, we developed specific primers (DB5-1F/DB5-1R). We recommend the adoption of the endophyte inoculation approach and molecular detection methods in forestry nurseries as valuable tools to enhance silvicultural practices and contribute to the conservation of C. kanehirae.

A Dark Septate Endophyte Improves Cadmium Tolerance of Maize by Modifying Root Morphology and Promoting Cadmium Binding to the Cell Wall and Phosphate.

Dark septate endophytes (DSEs) can improve the performance of host plants grown in heavy metal-polluted soils, but the mechanism is still unclear. A sand culture experiment was performed to investigate the effects of a DSE strain (Exophiala pisciphila) on maize growth, root morphology, and cadmium (Cd) uptake under Cd stress at different concentrations (0, 5, 10, and 20 mg·kg-1). The results indicated that the DSE significantly improved the Cd tolerance of maize, causing increases in biomass, plant height, and root morphology (length, tips, branch, and crossing number); enhancing the Cd retention in roots with a decrease in the transfer coefficient of Cd in maize plants; and increasing the Cd proportion in the cell wall by 16.0-25.6%. In addition, DSE significantly changed the chemical forms of Cd in maize roots, resulting in decreases in the proportions of pectates and protein-integrated Cd by 15.6-32.4%, but an increase in the proportion of insoluble phosphate Cd by 33.3-83.3%. The correlation analysis revealed a significantly positive relationship between the root morphology and the proportions of insoluble phosphate Cd and Cd in the cell wall. Therefore, the DSE improved the Cd tolerance of plants both by modifying root morphology, and by promoting Cd binding to the cell walls and forming an insoluble phosphate Cd of lower activity. These results of this study provide comprehensive evidence for the mechanisms by which DSE colonization enhances Cd tolerance in maize in root morphology with Cd subcellular distribution and chemical forms.

Microbiota-mediated nitrogen fixation and microhabitat homeostasis in aerial root-mucilage

BackgroundPlants sustain intimate relationships with diverse microbes. It is well-recognized that these plant-associated microbiota shape individual performance and fitness of host plants, but much remains to be explored regarding how they exert their function and maintain their homeostasis.ResultsHere, using pink lady (Heterotis rotundifolia) as a study plant, we investigated the phenomenon of microbiota-mediated nitrogen fixation and elucidated how this process is steadily maintained in the root mucilage microhabitat. Metabolite and microbiota profiling showed that the aerial root mucilage is enriched in carbohydrates and diazotrophic bacteria. Nitrogen isotope-labeling experiments, 15N natural abundance, and gene expression analysis indicated that the aerial root-mucilage microbiota could fix atmospheric nitrogen to support plant growth. While the aerial root mucilage is a hotspot of nutrients, we did not observe high abundance of other environmental and pathogenic microbes inside. We further identified a fungus isolate in mucilage that has shown broad-spectrum antimicrobial activities, but solely allows the growth of diazotrophic bacteria. This “friendly” fungus may be the key driver to maintain nitrogen fixation function in the mucilage microhabitat.3ZPiGYkoYjCtjUYKEqyz4oVideo ConclusionThe discovery of new biological function and mucilage-habitat friendly fungi provides insights into microbial homeostasis maintenance of microenvironmental function and rhizosphere ecology.

Different patterns and drivers of fungal communities between phyllosphere and rhizosphere in alpine grasslands

Abstract Epiphytic fungi are vital in enhancing their host plant performance and can also cause plant diseases. Generally, phyllosphere fungal community are majorly driven by climate, while rhizosphere fungal community are determined by soil properties and spatial distance. However, the differences in the relative effects of environmental factors on fungal community compositions and network structures remain far from clear between phyllosphere and rhizosphere. In this study, we conducted a large‐scale field survey along a 1400 km transect in the Tibetan Plateau and explored the composition and structure of phyllosphere and rhizosphere fungal communities from two dominant grass species (Leontopodium nanum and Stipa purpurea). L. nanum is widely distributed in relatively wet areas of alpine grasslands but S. purpurea prefers relatively dry areas. The geographical distributions of these two species overlap in the middle of the transect First, we found that precipitation was more important than temperature to affect fungal alpha diversity. High precipitation significantly promoted fungal alpha diversity in both phyllosphere and rhizosphere. Second, climate and spatial variables explained more variations in fungal community in the phyllosphere than rhizosphere. Specifically, greater precipitation promoted the relative abundances of pathotrophic fungi in the phyllosphere and rhizosphere, whereas lower precipitation only stimulated the relative abundances of symbiotrophic fungi in the rhizosphere. Third, precipitation had different impacts on phyllosphere and rhizosphere fungal networks between host species. Drought caused lower node number of fungal networks in the phyllosphere and rhizosphere of L. nanum. However, for S. purpurea, drought led to more complex and positive fungal networks in the phyllosphere and rhizosphere. Overall, these results indicated that precipitation caused different fungal community compositions along the transect between phyllosphere and rhizosphere, but consistently shaped their fungal networks. This study is among the first to provide compelling evidence on the large‐scale spatial variations and controlling factors for epiphytic fungal community in alpine grasslands. These new findings help to understand the role of epiphytic fungal community in affecting the functions of alpine grasses to cope with extreme environments. Read the free Plain Language Summary for this article on the Journal blog.

Onion Thrips (Thysanoptera: Thripidae) Host Plant Preference and Performance are Mediated by a Facultative Plant Pathogen of Onion.

Insect vector and phytopathogen interactions are mediated by host plants. Insects interact with pathogens directly or indirectly and they may prefer host plants based on infection status. Performance on infected hosts varies depending on the type of pathogen involved. Species specific studies of economically important insects and phytopathogens are needed to understand how these interactions impact crop yields. Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is an economically devastating insect pest of onions (Allium cepa L., Asparagales: Amaryllidaceae) worldwide and it co-occurs simultaneously with many different pathogens. Colletotrichum coccodes (Wallr) (Glomerellales: Glomerellaceae) is a generalist fungal pathogen that attacks onion foliage, causing tan lesions and decreasing yield. Onion thrips and C. coccodes represent two important pests of onions, but the relationship between onion thrips and C. coccodes infected onions has not been studied, and it is unclear if onion thrips contribute to the spread of C. coccodes in onion fields. A four-choice test with control, artificially injured, artificially injured + symptomatic, and inoculated-symptomatic onion suggests that onion thrips distinguish between hosts based on health status. Furthermore, a two-choice test with control, inoculated-asymptomatic, and inoculated-symptomatic onion pairings revealed that onion thrips distinguish between hosts based on infection status and prefer inoculated-symptomatic hosts. In a no-choice test, onion thrips numbers increased on inoculated-symptomatic plants compared to control or inoculated-asymptomatic plants. Overall, we found that onion thrips preferred and performed best on C. coccodes infected plants.

Timing of a plant-herbivore interaction alters plant growth and reproduction.

Phenological shifts have the potential to change species interactions, but relatively few studies have used experimental manipulations to examine the effects of variation in timing of an interspecific interaction across a series of life stages of a species. Although previous experimental studies have examined the consequences of phenological timing in plant-herbivore interactions for both plants and their herbivores, less is known about their effects on subsequent plant reproduction. Here, we conducted an experiment to determine how shifts in the phenological timing of monarch (Danaus plexippus) larval herbivory affected milkweed (Asclepias fascicularis) host plant performance, including effects on growth and subsequent effects on flower and seed pod phenology and production. We found that variation in the timing of herbivory affected both plant growth and reproduction, with measurable effects several weeks to several months after herbivory ended. The timing of herbivory had qualitatively different effects on vegetative and reproductive biomass: early-season herbivory had the strongest effects on plant size, whereas late-season herbivory had the strongest effects on the production of viable seeds. These results show that phenological shifts in herbivory can have persistent and qualitatively different effects on different life stages across the season.

Herbivory modifies plant symbiont number and impact on host plant performance in the field.

Species interactions are a unifying theme in ecology and evolution. Both fields are currently moving beyond their historical focus on isolated pairwise relationships to understand how ecological communities affect focal interactions. Additional species can modify both the number of interactions and the fitness consequences of each interaction (i.e., selection). Although only selection affects the evolution of the focal interaction, the two are often conflated, limiting our understanding of the evolution of multispecies interactions. We manipulated aboveground herbivory on the legume Medicago lupulina in the field and quantified its effect on number of symbionts and the per-symbiont impact on plant performance in two belowground symbioses: mutualistic rhizobia bacteria (Ensifer meliloti) and parasitic root-knot nematodes (Meloidogyne hapla). We found that herbivores modified the number of rhizobia nodules, as well as the benefit per nodule. However, each effect was specific to a distinct herbivory regime: natural herbivory affected nodule number, whereas leafhoppers (Cicadellidae) weakened the per nodule benefit. We did not detect any effect of herbivory on nematode gall number or the cost of infection. Our data demonstrate that distinguishing between symbiont number from the fitness consequences of symbiosis is crucial to accurately infer how pairwise interactions will evolve in a community.

Core Microbiota in the Rhizosphere of Heavy Metal Accumulators and Its Contribution to Plant Performance.

Persistent microbial symbioses can confer greater fitness to their host under unfavorable conditions, but manipulating such beneficial interactions necessitates a mechanistic understanding of the consistently important microbiomes for the plant. Here, we examined the phylogenetic profiles and plant-beneficial traits of the core microbiota that consistently inhabits the rhizosphere of four divergent Cd hyperaccumulators and an accumulator. We evidenced the existence of a conserved core rhizosphere microbiota in each plant distinct from that in the non-hyperaccumulating plant. Members of Burkholderiaceae and Sphingomonas were the shared cores across hyperaccumulators and accumulators. Several keystone taxa in the rhizosphere networks were part of the core microbiota, the abundance of which was an important predictor of plant Cd accumulation. Furthermore, an inoculation experiment with synthetic communities comprising isolates belonging to the shared cores indicated that core microorganisms could facilitate plant growth and metal tolerance. Using RNA-based stable isotope probing, we discovered that abundant core taxa overlapped with active rhizobacteria utilizing root exudates, implying that the core rhizosphere microbiota assimilating plant-derived carbon may provide benefits to plant growth and host phenotype such as Cd accumulation. Our study suggests common principles underpinning hyperaccumulator-microbiome interactions, where plants consistently interact with a core set of microbes contributing to host fitness and plant performance. These findings lay the foundation for harnessing the persistent root microbiomes to accelerate the restoration of metal-disturbed soils.

Association analyses of host genetics, root-colonizing microbes, and plant phenotypes under different nitrogen conditions in maize.

The root-associated microbiome (rhizobiome) affects plant health, stress tolerance, and nutrient use efficiency. However, it remains unclear to what extent the composition of the rhizobiome is governed by intraspecific variation in host plant genetics in the field and the degree to which host plant selection can reshape the composition of the rhizobiome. Here, we quantify the rhizosphere microbial communities associated with a replicated diversity panel of 230 maize (Zea mays L.) genotypes grown in agronomically relevant conditions under high N (+N) and low N (-N) treatments. We analyze the maize rhizobiome in terms of 150 abundant and consistently reproducible microbial groups and we show that the abundance of many root-associated microbes is explainable by natural genetic variation in the host plant, with a greater proportion of microbial variance attributable to plant genetic variation in -N conditions. Population genetic approaches identify signatures of purifying selection in the maize genome associated with the abundance of several groups of microbes in the maize rhizobiome. Genome-wide association study was conducted using the abundance of microbial groups as rhizobiome traits, and n=622 plant loci were identified that are linked to the abundance of n=104 microbial groups in the maize rhizosphere. In 62/104 cases, which is more than expected by chance, the abundance of these same microbial groups was correlated with variation in plant vigor indicators derived from high throughput phenotyping of the same field experiment. We provide comprehensive datasets about the three-way interaction of host genetics, microbe abundance, and plant performance under two N treatments to facilitate targeted experiments toward harnessing the full potential of root-associated microbial symbionts in maize production.

Phyllosphere bacterial and fungal communities vary with host species identity, plant traits and seasonality in a subtropical forest

BackgroundPhyllosphere microbes play important roles in host plant performance and fitness. Recent studies have suggested that tropical and temperate forests harbor diverse phyllosphere bacterial and fungal communities and their assembly is driven by host species identity and plant traits. However, no study has yet examined how seasonality (e.g. dry vs. wet seasons) influences phyllosphere microbial community assembly in natural forests. In addition, in subtropical forests characterized as the transitional zonal vegetation type from tropical to temperate forests, how tree phyllosphere microbial communities are assembled remains unknown. In this study, we quantified bacterial and fungal community structure and diversity on the leaves of 45 tree species with varying phylogenetic identities and importance values within a 20-ha lower subtropical evergreen broad-leaved forest plot in dry and wet seasons. We explored if and how the microbial community assembly varies with host species identity, plant traits and seasonality.ResultsPhyllosphere microbial communities in the subtropical forest are more abundant and diverse than those in tropical and temperate forests, and the tree species share a “core microbiome” in either bacteria or fungi. Variations in phyllosphere bacterial and fungal community assembly are explained more by host species identity than by seasonality. There is a strong clustering of the phyllosphere microbial assemblage amongst trees by seasonality, and the seasonality effects are more pronounced on bacterial than fungal community assembly. Host traits have different effects on community compositions and diversities of both bacteria and fungi, and among them calcium concentration and importance value are the most powerful explaining variables for bacteria and fungi, respectively. There are significant evolutionary associations between host species and phyllosphere microbiome.ConclusionsOur results suggest that subtropical tree phyllosphere microbial communities vary with host species identity, plant traits and seasonality. Host species identity, compared to seasonality, has greater effects on phyllosphere microbial community assembly, and such effects differ between bacterial and fungal communities. These findings advance our understanding of the patterns and drivers of phyllosphere microbial community assembly in zonal forests at a global scale.

Plant defences and spider-mite web affect host plant choice and performance of the whitefly Bemisia tabaci

Herbivores select host plants depending on plant quality and the presence of predators and competitors. Competing herbivores change host plant quantity through consumption, but they can also change plant quality through induction of plant defences, and this affects the performance of herbivores that arrive later on the plant. Some herbivores, such as the spider mite Tetranychus evansi, do not induce, but suppress plant defences, and later-arriving herbivores can profit from this suppression. It has been suggested that the dense web produced by this spider mite serves to prevent other herbivores to settle on the plant and benefit from the suppressed defences. Here, we confirmed this by studying the preference and performance of the whitefly Bemisia tabaci, a generalist herbivorous pest. To disentangle the effects through changes in plant defences from the effects of spider-mite web, we included treatments with a strain of the closely-related web-producing spider mite T. urticae, which induces plant defences. Whiteflies did perform worse on plants with defences induced by T. urticae, but, in contrast to other herbivores, did not perform better on plants with defences suppressed by T. evansi. Moreover, the web of both spider mites reduced the juvenile survival of whiteflies, and whiteflies avoided plants that were covered with web. Hence, whitefly performance was not only affected by plant quality and induced plant defences, but also through the web produced by spider mites, which thus serves to protect against potential competitors, especially when these could profit from the suppression of plant defences by the mites.

Salinity legacy: Foliar microbiome's history affects mutualist-conferred salinity tolerance.

The rapid human-driven changes in the environment during the Anthropocene have placed extreme stress on many plants and animals. Beneficial interactions with microorganisms may be crucial for ameliorating these stressors and facilitating the ecosystem services host organisms provide. Foliar endophytes, microorganisms that reside within leaves, are found in essentially all plants and can provide important benefits (e.g., enhanced drought tolerance or resistance to herbivory). However, it remains unclear how important the legacy effects of the abiotic stressors that select on these microbiomes are for affecting the degree of stress amelioration provided to their hosts. To elucidate foliar endophytes' role in host-plant salt tolerance, especially if salinity experienced in the field selects for endophytes that are better suited to improve the salt tolerance of their hosts, we combined field collections of 90 endophyte communities from 30 sites across the coastal Everglades with a manipulative growth experiment assessing endophyte inoculation effects on host-plant performance. Specifically, we grew >350 red mangrove (Rhizophora mangle) seedlings in a factorial design that manipulated the salinity environment the seedlings experienced (freshwater vs. saltwater), the introduction of field-collected endophytes (live vs. sterilized inoculum), and the legacy of salinity stress experienced by these introduced endophytes, ranging from no salt stress (0parts per thousand [ppt] salinity) to high salt stress (40 ppt) environments. We found that inoculation with field-collected endophytes significantly increased mangrove performance across almost all metrics examined (15%-20% increase on average), and these beneficial effects typically occurred when the endophytes were grown in saltwater. Importantly, our study revealed the novel result that endophyte-conferred salinity tolerance depended on microbiome salinity legacy in a key coastal foundation species. Salt-stressed mangroves inoculated with endophyte microbiomes from high-salinity environments performed, on average, as well as plants grown in low-stress freshwater, while endophytes from freshwater environments did not relieve host salinity stress. Given the increasing salinity stress imposed by sea level rise and the importance of foundation species like mangroves for ecosystem services, our results indicate that consideration of endophytic associations and their salinity legacy may be critical for the successful restoration and management of coastal habitats.

Genome-Scale Modeling Specifies the Metabolic Capabilities of Rhizophagus irregularis.

ABSTRACTRhizophagus irregularis is one of the most extensively studied arbuscular mycorrhizal fungi (AMF) that forms symbioses with and improves the performance of many crops. Lack of transformation protocol for R. irregularis renders it challenging to investigate molecular mechanisms that shape the physiology and interactions of this AMF with plants. Here, we used all published genomics, transcriptomics, and metabolomics resources to gain insights into the metabolic functionalities of R. irregularis by reconstructing its high-quality genome-scale metabolic network that considers enzyme constraints. Extensive validation tests with the enzyme-constrained metabolic model demonstrated that it can be used to (i) accurately predict increased growth of R. irregularis on myristate with minimal medium; (ii) integrate enzyme abundances and carbon source concentrations that yield growth predictions with high and significant Spearman correlation ( = 0.74) to measured hyphal dry weight; and (iii) simulate growth rate increases with tighter association of this AMF with the host plant across three fungal structures. Based on the validated model and system-level analyses that integrate data from transcriptomics studies, we predicted that differences in flux distributions between intraradical mycelium and arbuscles are linked to changes in amino acid and cofactor biosynthesis. Therefore, our results demonstrated that the enzyme-constrained metabolic model can be employed to pinpoint mechanisms driving developmental and physiological responses of R. irregularis to different environmental cues. In conclusion, this model can serve as a template for other AMF and paves the way to identify metabolic engineering strategies to modulate fungal metabolic traits that directly affect plant performance.IMPORTANCE Mounting evidence points to the benefits of the symbiotic interactions between the arbuscular mycorrhiza fungus Rhizophagus irregularis and crops; however, the molecular mechanisms underlying the physiological responses of this fungus to different host plants and environments remain largely unknown. We present a manually curated, enzyme-constrained, genome-scale metabolic model of R. irregularis that can accurately predict experimentally observed phenotypes. We show that this high-quality model provides an entry point into better understanding the metabolic and physiological responses of this fungus to changing environments due to the availability of different nutrients. The model can be used to design metabolic engineering strategies to tailor R. irregularis metabolism toward improving the performance of host plants.

Potato plant variety affects the performance and oviposition preference of Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae).

Damage by the potato tuber moth Phthorimaea operculella is one of the major constraints to commercial production of potato in many areas of the world. To promote effective pest management practices for P. operculella based on host plant, larval and adult performance of P. operculella fed on Lishu 6, Hezuo 88, Yunshu 304, and Qingshu 9 potato varieties was compared by examining their survival rate, larval feeding, pupal weight, and oviposition preference. Compared with larvae fed on the other three potato plants, those fed on Lishu 6 exhibited the highest survival rate, with almost 61.67% developing to the adult stage. Females also preferred to lay their eggs on Lishu 6 over Hezuo 88, Yunshu 304 and Qingshu 9; and the weight of P. operculella pupa on Lishu 6 plant (0.0085 g) was significantly heavier than that of on others, especially on Qingshu 9 (0.0062 g). Moreover, first instar larvae fed on Lishu 6 showed host preference to Qingshu 9. This study demonstrated that Lishu 6 is susceptible to P. operculella, and Qingshu 9 is not relatively susceptible to P. operculella, which suggested that the P. operculella feeding responses to dominant potato varieties in China is different. This variation can be applied for the potato breeding and pest management practice. © 2021 Society of Chemical Industry.