Host Plant Research Articles

Lethal and sublethal effects of Citrus aurantium and Citrus sinensis essential oils and their major component limonene on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is an insect pest with great socio-economic importance in different agricultural regions worldwide. This species is highly adaptive and polyphagous, feeding on wild and cultivated host plants. Successive pesticide applications, which negatively affect the environment, are mainly used for managing H. armigera. Studies have investigated alternative methods with low environmental and socioeconomic impacts, including using essential oils. Essential oils are secondary plant-derived metabolites with insecticidal activity in different insect pest populations. Thus, the objective of this study was to evaluate the insecticidal activity of essential oils of Citrus aurantium (Linnaeus) (Rutaceae) and Citrus sinensis (Linnaeus) (Rutaceae) as well as their major component limonene on the biology and reproduction of H. armigera. The essential oils were characterized using gas chromatography-mass spectrometry. Further, their toxicity and the effects of their lethal and sublethal concentrations in larvae and on biological and reproductive parameters in adults were evaluated. All treatments exhibited insecticidal activity and lethal and sub-lethal effects on the biology and reproduction of H. armigera. Therefore, these essential oils could be used to control H. armigera.

Mechanistic Insight into the Anti-Alternaria Activity of Bimetallic Zinc Oxide and Silver/Zinc Oxide Nanoparticles

Alternaria alternata is an opportunistic phytopathogen that negatively impact the growth and production of a wide variety of host plants. In this study, we evaluated the antifungal potential of biogenic ZnO, and bimetallic silver and zinc oxide (Ag/ZnO) nanoparticles synthesized using seed extract of Abrus precatorious and characterized using different analytical tools. In vitro antifungal potentials of ZnO and Ag/ZnO nanoparticles were carried out using the food poison technique. Morphological and ultrastructure of the A. alternata treated with the nanoparticles were carried out using high resolution scanning and transmission electron microscopy (HRSEM and HRTEM). In addition, changes in polysaccharide production, chitin content and enzymatic (cellulase and lipase) activities of A. alternata were assayed. Double peak signifying a UVmax of 353.88 and 417.25 nm representing Ag and ZnO respectively was formed in the bimetallic nanoparticles. HRSEM and HRTEM results shows agglomerated nanoparticles with particle and crystallite size of 23.94 and 16.84 nm for ZnO nanoparticles, 35.12 and 28.99 nm for Ag/ZnO nanoparticles respectively. In vitro antifungal assay shows a significant concentration-dependent inhibition (p<0.05) of A. alternata mycelia with highest percentage inhibition of 73.93% (ZnO nanoparticles) and 68.26 % (Ag/ZnO nanoparticles) at 200 ppm. HRSEM and HRTEM micrographs of the treated A. alternata mycelia shows alteration of the cellular structure, clearance of the cytoplasmic organelles and localization of the nanoparticles within the cell. A. alternata treated with 200 ppm nanoparticles show a significant decrease (p<0.05) in the polysaccharides and chitin contents, cellulase and lipase activities. The results suggests that ZnO and Ag/ZnO nanoparticles mode of action may be via alteration of the fungal cell wall through the inhibition of polysaccharides, chitin, cellulases and lipases synthesis. ZnO and Ag/ZnO nanoparticles may be a promising tool for the management and control of disease causing fungal phytopathogens.

The nematode effector Mj-NEROSs interacts with Rieske's iron-sulfur protein influencing plastid ROS production to suppress plant immunity.

Root-knot nematodes (RKN; Meloidogyne species) are plant pathogens that introduce several effectors in their hosts to facilitate infection. The actual targets and functioning mechanism of these effectors largely remain unexplored. This study illuminates the role and interplay of the Meloidogyne javanica nematode effector ROS suppressor (Mj-NEROSs) within the host plant environment. Mj-NEROSs suppresses INF1-induced cell death as well as flg22-induced callose deposition and reactive oxygen species (ROS) production. A transcriptome analysis highlighted the downregulation of ROS-related genes upon Mj-NEROSs expression. NEROSs interacts with the plant Rieske's iron-sulfur protein (ISP) as shown by yeast-two-hybrid and bimolecular fluorescence complementation. Secreted from the subventral pharyngeal glands into giant cells, Mj-NEROSs localizes in the plastids where it interacts with ISP, subsequently altering electron transport rates and ROS production. Moreover, our results demonstrate that isp Arabidopsis thaliana mutants exhibit increased susceptibility to M. javanica, indicating ISP importance for plant immunity. The interaction of a nematode effector with a plastid protein highlights the possible role of root plastids in plant defense, prompting many questions on the details of this process.

Spatial Distribution and Community Composition of Endophytic Fungi within Mussaenda pubescens Stems

Endophytic fungi, pivotal in facilitating plant co-evolution, significantly enhance plant growth, stress resistance, and environmental adaptability. Despite their importance, the spatial distribution of stem endophytic fungi (SEF) within host plants remains poorly characterized. Here, we employed high-throughput sequencing to conduct a comparative analysis of SEF communities in Mussaenda pubescens on a regional scale. Our findings reveal that whole-SEF communities were overwhelmingly dominated by members of the phylum Ascomycota, accounting for 85.9%, followed by Basidiomycota at 13.9%, and that alpha diversity within the whole-SEF community of M. pubescens remains relatively consistent across sampling sites. However, significant variation was observed within conditionally abundant taxa (CAT), conditionally rare or abundant taxa (CRAT), and conditionally rare taxa (CRT). Climatic factors emerged as the primary influence on SEF community distribution, followed by spatial distance and stem chemical properties. Neutral community modeling results suggest that both stochastic and deterministic processes play a role in shaping whole-SEF communities, with deterministic processes having a stronger influence on CRT subcommunities. Furthermore, the CRT co-occurrence network exhibited a more complex structure, characterized by higher values of network betweenness and degree relative to CAT and CRAT subcommunities. These findings enhance our understanding of community assembly and ecological interactions between stem fungal endophytes, presenting opportunities for harnessing fungal resources for the benefit of humanity.

Foraging ants affect community composition and diversity of phyllosphere fungi on a myrmecophilous plants, Mallotus japonicus.

Many microorganisms inhabit the aboveground parts of plants (i.e. the phyllosphere), which mainly comprise leaves. Understanding the structure of phyllosphere microbial communities and their drivers is important because they influence host plant fitness and ecosystem functions. Despite the high prevalence of ant-plant associations, few studies have used quantitative community data to investigate the effects of ants on phyllosphere microbial communities. In the present study, we investigated the effects of ants on the phyllosphere fungal communities of Mallotus japonicus using high-throughput sequencing. Mallotus japonicus is a myrmecophilous plants that bears extrafloral nectaries, attracting several ant species, but does not provide specific ant species with nest sites like myrmecophytes do. We experimentally excluded ants with sticky resins from the target plants and collected leaf discs to extract fungal DNA. The ribosomal DNA internal transcribed spacer 1 (ITS1) regions of the phyllosphere fungi were amplified and sequenced to obtain fungal community data. Our results showed that the exclusion of ants changed the phyllosphere fungal community composition; however, the effect of ants on OTU richness was not clear. These results indicate that ants can change the community of phyllosphere fungi, even if the plant is not a myrmecophyte.

Caterpillar movement mediates spatially local interactions and determines the relationship between population density and contact.

While interactions in nature are inherently local, ecological models often assume homogeneity across space, allowing for generalization across systems and greater mathematical tractability. Density-dependent disease models are a prominent example of models that assume homogeneous interactions, leading to the prediction that disease transmission will scale linearly with population density. In this study, we examined how the scale of larval butterfly movement interacts with the resource landscape to influence the relationship between larval contact and population density in the Baltimore checkerspot (Euphydryas phaeton). Our study was inspired by the recent discovery of a viral pathogen that is transmitted horizontally among Baltimore checkerspot larvae. We used multi-year larvae location data across six Baltimore checkerspot populations in the eastern U.S. to test whether larval nests are spatially clustered. We then integrated these spatial data with larval movement data in different resource contexts to investigate whether heterogeneity in spatially local interactions alters the assumed linear relationship between larval nest density and contact. We used Correlated Random Walk (CRW) models and field observations of larval movement behavior to construct Probability Distribution Functions (PDFs) of larval dispersal, and calculated the overlap in these PDFs to estimate conspecific contact within each population. We found that all populations exhibited significant spatial clustering in their habitat use. Subsequent larval movement rates were influenced by encounters with host plants and larval age, and under many movement scenarios, the scale of predicted larval movement was not sufficient to allow for the "homogeneous mixing" assumed in density dependent disease models. Therefore, relationships between population density and larval contact were typically non-linear. We also found that observed use of available habitat patches led to significantly greater contact than would occur if habitat use were spatially random. These findings strongly suggest that incorporating larval movement and spatial variation in larval interactions is critical to modeling disease outcomes in E. phaeton. Epidemiological models that assume a linear relationship between population density and larval contact have the potential to underestimate transmission rates, especially in small populations that are already vulnerable to extinction.

Review of the Newly Established amictus-Subgroup of the Genus Leptocoris (Hemiptera: Heteroptera: Rhopalidae), with the Description of a New Species from the Arabian Peninsula

Leptocoris arabicus new species (Hemiptera: Heteroptera: Rhopalidae: Serinethinae) is described based on 55 specimens of both sexes collected in various localities of southern Oman and southeastern Yemen; a hypothesis is proposed as to its host plant. The new species is close to Leptocoris amictus Germar, 1838 and to Leptocoris ruber Göllner-Scheiding, 1980, new status, due to the presence of a produced horned process along the posterior ventral margin of the genital capsule. It is distinguished from both by differences in colour pattern and morphology. An informal L. amictus species-subgroup is proposed to accommodate these three species within the Leptocoris hexophthalmus species-group sensu Göllner-Scheiding (1980). The following new faunistic records are also provided: L. amictus from Ethiopia, Mozambique and Zambia; L. ruber from Central African Republic. The occurrence of L. chevreuxi (Noualhier, 1893) in Oman is confirmed. The list of all available species-group names assigned to Leptocoris Hahn, 1833 (gender masculine) and their synonyms is compiled and the gender agreement is corrected in the species names when appropriate. The nomenclatural problem concerning Leptocoris living on Marshall Islands discovered by Kerzhner (2003) is discussed and the following corrections are provided: Leptocoris rufus rufus Hahn, 1833, new status = Leptocoris lariversi Usinger, 1952, new synonymy, and Leptocoris rufus isolatus (Distant, 1914) new status.

Reevaluation of taxonomic identity of the recently introduced invasive planthopper, Pochazia shantungensis (Chou &amp; Lu, 1977) (Hemiptera: Fulgoroidea: Ricaniidae) in Japan

The taxonomic identity of the invasive Asian Ricaniid planthopper, Pochazia shantungensis (Chou &amp; Lu, 1977) in Japan is reevaluated. This originally Chinese planthopper is highly polyphagous and has recently become an important pest in Korea. In 2015, this species was first documented from Sakai, Osaka Prefecture and has been widespread since then. The genital structures, wings and fifth instar nymph are described and illustrated. The host plants in Japan are also documented with photographs. The male genitalia of a similar species, P. sublimata (Jacobi, 1916), are illustrated as well. As a recently introduced pest in Japan, P. shantungensis needs to be monitored for its potential spread and for the damage it may cause to agriculture.

Physiological Measurements and Transcriptomics Reveal the Fitness Costs of Monochamus saltuarius to Bursaphelenchus xylophilus.

The pine wood nematode (PWN) uses several Monochamus species as vehicles, through a temporary hitchhiking process known as phoresy, enabling it to access new host plant resources. Monochamus saltuarius acts as a new and major vector of the PWN in Northeastern China, showing lower PWN carrying capacity and a shorter transmission cycle compared to established vectors. The apparently altered symbiotic relationship offers an interesting area for researching the costs and adaptions involved in nematode-beetle, a specialized phoresy. We analyzed the response and fitness costs of M. saltuarius through physiological measurements and transcriptomics. The PWN exerted adverse repercussions on the growth and development of M. saltuarius. The PWN accelerated larval development into pupae, while beetle adults carrying the PWN exhibited an elevated abnormality rate and mortality, and reduced starvation resistance. During the pupal stage, the expression of growth-related genes, including ecdysone-inducible genes (E74EA), cuticle proteins, and chitin genes (CHTs), markedly increased. Meanwhile, the induced immune response, mainly by the IMD and Toll signaling pathways, could be a contributing factor to adult abnormality and mortality. Adult gonads and trachea exhibited enrichment in pathways related to fatty acid elongation, biosynthesis, and metabolism. FASN, ELOVL, and SCD possibly contributed to resistance against PWN. Our research indicated that phoretic interactions between vector beetles and PWN vary throughout the vector's lifespan, particularly before and after entry into the trachea. This study highlighted the fitness costs of immunity and metabolism on the vector beetle, indicating the adaptation mechanisms and evolutionary trade-offs to PWN.

First Report of Fusarium falciforme Causing Root and Rhizome Rot of Epimedium sagittatum in China.

Epimedium sagittatum (Sieb.et Zucc.) Maxim., a perennial herb, is an important medicinal plant, rich in flavonoids, and widely used in the treatment of sexual dysfunction, rheumatic disease, and cancers (Tan et al. 2016). In July 2022, a disease of root and rhizome was found on E. sagittatum aged 1-8 years in a planting area (266 ha) of Zhumadian City (32°58'12" N, 114°37'48" E), Henan Province, China. The disease incidence per field (660 m2) was around 10-15% in six randomly surveyed fields planted with about 10,000 E. sagittatum plants each. Symptoms included leaf yellowing, root and rhizome browning, rotting and necrosis, and eventually the whole plant wilted and died. Fifteen plants with symptoms were sampled to isolate the pathogen. Symptomatic tissues were cut into small pieces of 5×5 mm, surface sterilized with 75% ethanol for 30 s, followed by three rinses with sterile double-distilled water (ddH2O). The pieces were then surface disinfected with 0.1% HgCl2 for 30 s, rinsed three times with sterile ddH2O, placed onto potato dextrose agar (PDA) plates and incubated at 28°C in the dark for 5 days. Twelve deferent Fusarium spp. colonies were purified by excising hyphal tip onto PDA for cultivation. Pathogenicity test of all strains was performed. Only isolate GY2 could result in root and rhizome rot of host plant. Colonies of GY2 on PDA had abundant white aerial mycelia with yellow halo. Macroconidia were hyaline, falciform, with a slightly curved apical cell and blunt basal cell, 29.7~45.0 (average 38.3) × 4.5~6.6 (average 5.3) µm (n =50), with 2-3 septa. Microconidia were oval, or reniform, hyaline, 8.4~26.5 (average 16.5) × 2.7~6.0 (average 4.5) µm (n =50), with 0-2 septa. Morphological characteristics of isolate GY2 were consistent with those of the Fusarium solani species complex (FSSC) (Chehri et al. 2015). For molecular identification, a region of the translation elongation factor 1-α (TEF) and RNA polymerase second largest subunit (RPB2) of GY2 were PCR-amplified and sequenced using the primers EF1-728F/986R (Carbone et al. 1999) and RPB2-5f2/7cr (O'Donnell et al. 2010), respectively. The TEF and RPB2 sequences (GenBank accession nos. OR978135.1 and OR978136.1) of GY2 were concatenated for a phylogenetic analysis using the Bayesian method (Zhang et al. 2020). The phylogenetic tree revealed that isolate GY2 clustered with F. falciforme with a credibility value of 99%. Morphological and molecular results support identification of isolate GY2 as F. falciforme. A pathogenicity test was performed on 4-year-old healthy plants grown in pots. Twenty healthy plants were inoculated by pouring a 200 mL conidial suspension (1×106 conidia/mL) around the rhizome. Control plants received 200 mL of sterile ddH2O. All treatments were maintained in a greenhouse at 25±1°C and 80% relative humidity. The assay was conducted three times. After 20 days, similar symptoms as those in the field were observed on the inoculated plants, whereas controls remained asymptomatic. Fusarium falciforme was reisolated from the symptomatic plants and showed the same morphological and molecular characteristics as isolate GY2, fulfilling Koch's postulates. Fusarium falciforme was reported to cause root rot of tobacco (Qiu et al. 2023) and industrial hemp (Paugh et al. 2022). However, this is the first report of F. falciforme causing root and rhizome rot of E. sagittatum. Our study will contribute to the development of strategies for the effective management of this disease on E. sagittatum.

Incredible Host Diversity and Regional Potential Distribution of an Oriental Parasitic Plant (Taxillus yadoriki)

This study investigates the host diversity and characteristics of the rare parasitic plant Silverberry-like taxillus (Taxillus yadoriki). Seogwipo, Jeju Island, where T. yadoriki grows naturally, was examined to clarify the diversity of host species, their location, and the part of the tree where T. yadoriki is attached. A total of 687 host trees were found. Taxillus yadoriki was intensively distributed in the lowlands below 200 m a.s.l. The host trees belonged to 40 species, four varieties, three cultivars, and two hybrids from 32 genera and 21 families, of which 23 taxa were identified as host plants for the first time in this study. Incredibly, this plant was found to be able to parasitize a variety of plants from 12 orders. Taxillus yadoriki was found to be parasitic in three orders of Gymnosperms, Ginkgoales, Cupressales, and Pinales, as well as nine orders of Angiosperms, including Magnoliales, Rosales, and Ericales. Rosaceae was the most diverse at 18.0%, and most species were broad-leaved and arboreal. Among them, Cryptomeria japonica and Litsea japonica had the highest frequency of parasitization and T. yadoriki was mainly attached to the upper part of the main tree and the main branch; as a result, T. yadoriki was distributed and showed specificity in the position of disturbance on the host. T. yadoriki’s specific distribution model was built as a Maxent program. The area under the curve of the receiver operation characteristic was 0.948 ± 0.026 (mean ± standard deviation), and the performance of the constructed model was excellent. Of the total eight environmental factors, density of artistic forest and meant temperature of coldest quarter accounted for 75.3% of the total importance, which was the main distribution determinant of species. In the average distribution probability map of T. yadoriki, the critical probability for determining distribution was calculated to be 0.2898 ± 0.1018. Accordingly, the distribution of species is predicted to expand from Jeju Island to the entire southern and southeastern coasts.

CULTURABLE ENDOSYMBIOTIC BACTERIA FROM THE INDIAN LAC INSECT, KERRIA LACCA (KERR)

The Indian lac insect, Kerria lacca (Kerr) (Coccoidea: Tachardiidae) is a commercially important phytosuccivorous and sessile scale insect. Lac insects are cultured on suitable host plants in India and some Southeast Asian countries to produce lac. The lac insect harbours a number of endosymbionts. Isolation of culturable microbial endosymbionts and their identification through 16S rRNA has revealed sex and host-related differences of microbial species. Bacillus boroniphilus, Enterobacter cloacae and Staphylococcus sp. were found only in the lac insects reared on the plant host Cajanus cajan, whereas Bacillus firmus, Lysinibacillus xylanilyticus, Bacillus horneckiae and Bacillus velezensis were recorded only from Flemingia macrophylla. B. firmus and L. xylanilyticus were female-specific and B. horneckiae and B. velezensis were male-specific with Flemingia macrophylla as host; E. cloacae was female-specific and Bacillus boroniphilus and Staphylococcus sp. were male specific with C. cajan. Biochemical characteristics of the isolates, their genetic relationship with their taxonomic kin and their probable role, based on the information available about these endosymbionts in other hosts, have been studied.

Distribution and host plant associations of Megachile (Pseudomegachile) lanata (Fabricius, 1775) (Megachilidae) in Pothohar, Pakistan

Solitary Megachile lanata (Fabricius) are important pollinator of a variety of plants including horticultural, ornamental, aromatic and agricultural crops based on their prevalence and floral host plant range. Their presence can greatly increase the yield and quality of the crops they pollinate. Explore the occurrence and floral host plant range of Megachile (Pseudomegachile) lanata within the Pothohar plateau, Punjab, Pakistan. The specimens of Megachile lanata (Fabricius) were collected on a monthly basis from various agricultural and all other types of landscapes, such as forests, urban areas and natural habitats in the Pothohar plateau of Punjab, Pakistan during 2021-2022. The individuals of this bee were collected with an aerial net. Present study investigate seasonal population and distribution range of M. lanata. Herein, we have observed twelve host plants in various localities of study area. This is an invasive species and one distinct feature is the inclusion of brief diagnostic information, details about host plants as well as information on ecology and current distribution in Pakistan. This data will contribute to a better understanding of solitary Megachile lanata (Fabricius) bee species diversity and abundance, which is crucial for maintaining the health of ecosystems, especially those in agro-ecosystems on Pothohar Plateau of Punjab, Pakistan.

Life history and overwintering in multi‐ and univoltine species of family Tephritidae in a subtropical region of northwestern Argentina

AbstractAmong phytophagous insects, life history often evolves as a strategy to cope with seasonality in host plant availability. Whereas specialization often leads to dormancy, aestivation, or longevity, polyphagous species bridge between periods of host availability by exploiting alternative host plants. The aim of the present work was to characterize the life histories of four species of specialist and generalist uni‐ and multivoltine frugivorous fruit flies – Ceratitis capitata Wiedemann, Anastrepha fraterculus Wiedemann, Rhagoletis blanchardi Aczel, and Rhagoletotrypeta pastranai Aczel (all Diptera: Tephritidae) – inhabiting in sympatry in Las Yungas phytogeographical province in Tucumán (northwestern Argentina). For this purpose, infested host plant fruits were sequentially collected during two consecutive years, and flies recovered from these fruits were subjected to demographic experiments to establish longevity and overwintering mechanisms. The results indicated that life cycles were tightly related to host fruit availability, where multivoltine species sequentially exploit different host plants over the year, whereas univoltine species must undergo pupal dormancy to reach the next host fructification period and may extend the duration of dormancy when climatic conditions are acyclic and unpredictable. The present study may broaden knowledge about diapausing Tephritidae in subtropical regions and may contribute to an increased conceptual basis for the improvement of pest control strategies, such as the sterile insect technique (SIT).

UDP-glycosyltransferases act as key determinants of host plant range in generalist and specialist Spodoptera species

Phytophagous insects have evolved sophisticated detoxification systems to overcome the antiherbivore chemical defenses produced by many plants. However, how these biotransformation systems differ in generalist and specialist insect species and their role in determining insect host plant range remains an open question. Here, we show that UDP-glucosyltransferases (UGTs) play a key role in determining the host range of insect species within the Spodoptera genus. Comparative genomic analyses of Spodoptera species that differ in host plant breadth identified a relatively conserved number of UGT genes in generalist species but high levels of UGT gene pseudogenization in the specialist Spodoptera picta. CRISPR-Cas9 knockouts of the three main UGT gene clusters of Spodoptera frugiperda revealed that UGT33 genes play an important role in allowing this species to utilize the poaceous plants maize, wheat, and rice, while UGT40 genes facilitate utilization of cotton. Further functional analyses in vivo and in vitro identified the UGT SfUGT33F32 as the key mechanism that allows generalist S. frugiperda to detoxify the benzoxazinoid DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one), a potent insecticidal phytotoxin produced by poaceous plants. However, while this detoxification capacity is conserved in several generalist Spodoptera species, Spodoptera picta, which specializes on Crinum plants, is unable to detoxify DIMBOA due to a nonfunctionalizing mutation in SpUGT33F34. Collectively, these findings provide insight into the role of insect UGTs in host plant adaptation, the mechanistic basis of evolutionary transitions between generalism and specialism and offer molecular targets for controlling a group of notorious insect pests.

Bacillus tequilensis influences metabolite production in tomato and restores soil microbial diversity during Fusarium oxysporum infection.

This study evaluates cellular damage, metabolite profiling, and defence-related gene expression in tomato plants and soil microflora during Fusarium wilt disease after treatment with B. tequilensis PBE-1. Histochemical analysis showed that PBE-1 was the primary line of defence through lignin deposition and reduced cell damage. GC-MS revealed that PBE-1 treatment ameliorated stress caused by F. oxysporum infection. PBE-1 also improved transpiration, photosynthesis, and stomatal conductance in tomato. qRT-PCR suggested that the defence-related genes FLS2, SERK, NOS, WRKYT, NHO, SAUR, and MYC2, which spread infection, were highly upregulated during F. oxysporum infection, but either downregulated or expressed normally in PBE-1 + P treated plants. This indicates that the plant not only perceives the bio-control agent as a non-pathogen entity but its presence in normal metabolism and gene expression within the host plant is maintained. The study further corroborated findings that application of PBE-1 does not cause ecological disturbances in the rhizosphere. Activity of soil microflora across four treatments, measured by Average Well Colour Development (AWCD), showed continuous increases from weeks 1 to 4 post-pathogen infection, with distinct substrate usage patterns like tannic and fumaric acids impacting microbial energy source utilization and diversity. Principal Component Analysis (PCA) and diversity indices like McIntosh, Shannon, and Simpson further illustrated significant microbial community shifts over the study period. In conclusion, our findings demonstrate that B. tequilensis PBE-1 is an ideal bio-agent for field application during Fusarium wilt disease management in tomato.

Molecular Mechanisms and Cytopathology of Phytophthora: Strategies, Interactions and Future Perspectives

Phytophthora is an aggressive plant pathogen, pose substantial threats to global agriculture, leading to extensive crop losses. Controlling Phytophthora diseases remains challenging, with limited effective methods available. Host resistance emerges as a promising strategy, but its sustainability hinges on a profound comprehension of the intricate molecular dynamics governing Phytophthora-plant interactions. These interactions unveil a hemi-biotrophic lifestyle of Phytophthora, transitioning from biotrophic to necrotrophic phases during infection. The infection process involves a series of orchestrated events, including chemotactic attraction, penetration, and sporulation on the host surface. Molecular cytology elucidates a sophisticated interplay between Phytophthora and plant defense mechanisms. Phytophthora elicits defense responses in host plants through the release of elicitor molecules, triggering PAMP Triggered Immunity (PTI) responses such as antimicrobial compound production and cell wall fortification. Detection and recognition of Phytophthora effectors instigate a second layer of defense in resistant plants, leading to Effector Triggered Immunity (ETI) and hypersensitive response. In response, virulent strains evolve altered effectors to evade detection and suppress host defenses, underscoring the ongoing molecular coevolution between Phytophthora and plants. The pathogenic success of Phytophthora species is attributed to their diverse and rapidly evolving effector gene complements, targeting various host proteins and cellular processes. Future strategies for combating Phytophthora diseases include genome editing using CRISPR/Cas-9 technology to enhance plant immunity and the identification of non-race-specific resistance sources for broad-spectrum protection. In essence, a comprehensive understanding of Phytophthora-plant interactions at the molecular level is imperative for devising effective strategies to mitigate their impact on global agriculture.

Potyviral Helper-Component Protease: Multifaced Functions and Interactions with Host Proteins.

The best-characterized functional motifs of the potyviral Helper-Component protease (HC-Pro) responding for aphid transmission, RNA silencing suppression, movement, symptom development, and replication are gathered in this review. The potential cellular protein targets of plant virus proteases remain largely unknown despite their multifunctionality. The HC-Pro catalytic domain, as a cysteine protease, autoproteolytically cleaves the potyviral polyproteins in the sequence motif YXVG/G and is not expected to act on host targets; however, 146 plant proteins in the Viridiplantae clade containing this motif were searched in the UniProtKB database and are discussed. On the other hand, more than 20 interactions within the entire HC-Pro structure are known. Most of these interactions with host targets (such as the 20S proteasome, methyltransferase, transcription factor eIF4E, and microtubule-associated protein HIP2) modulate the cellular environments for the benefit of virus accumulation or contribute to symptom severity (interactions with MinD, Rubisco, ferredoxin) or participate in the suppression of RNA silencing (host protein VARICOSE, calmodulin-like protein). On the contrary, the interaction of HC-Pro with triacylglycerol lipase, calreticulin, and violaxanthin deepoxidase seems to be beneficial for the host plant. The strength of these interactions between HC-Pro and the corresponding host protein vary with the plant species. Therefore, these interactions may explain the species-specific sensitivity to potyviruses.

Fungal endophytes from saline-adapted shrubs induce salinity stress tolerance in tomato seedlings

Abstract To meet the food and feed demands of the growing population, global food production needs to double by 2050. Climate change-induced challenges to food crops, especially soil salinization, remain a major threat to food production. We hypothesize that endophytic fungi isolated from salt-adapted host plants can confer salinity stress tolerance to salt-sensitive crops. Therefore, we isolated fungal endophytes from shrubs along the shores of saline alkaline Lake Magadi and evaluated their ability to induce salinity stress tolerance in tomato seeds and seedlings. Of 60 endophytic fungal isolates, 95% and 5% were from Ascomycetes and Basidiomycetes phyla, respectively. The highest number of isolates (48.3%) were from the roots. Amylase, protease, and cellulase were produced by 25, 30, and 27 isolates, respectively; and 32 isolates solubilized phosphate. Only 8 isolates grew at 1.5 M NaCl. Four fungal endophytes (Cephalotrichum cylindricum, Fusarium equiseti, Fusarium falciforme, and Aspergilus puniceus) were tested under greenhouse conditions for their ability to induce salinity tolerance in tomato seedlings. All four endophytes successfully colonized tomato seedlings and grew in 1.5 M NaCl. The germination of endophyte-inoculated seeds was enhanced by 23% %, whereas seedlings showed increased chlorophyll and biomass content and decreased hydrogen peroxide content under salinity stress, as compared to control. The results suggest that the the four isolates can potentially be used to mitigate salinity stress in tomato plants in salt-affected soils.

Horizontal gene transfer in plant microbiomes: integrons as hotspots for cross-species gene exchange.

Plant microbiomes play important roles in plant health and fitness. Bacterial horizontal gene transfer (HGT) can influence plant health outcomes, driving the spread of both plant growth-promoting and phytopathogenic traits. However, community dynamics, including the range of genetic elements and bacteria involved in this process are still poorly understood. Integrons are genetic elements recently shown to be abundant in plant microbiomes, and are associated with HGT across broad phylogenetic boundaries. They facilitate the spread of gene cassettes, small mobile elements that collectively confer a diverse suite of adaptive functions. Here, we analysed 5,565 plant-associated bacterial genomes to investigate the prevalence and functional diversity of integrons in this niche. We found that integrons are particularly abundant in the genomes of Pseudomonadales, Burkholderiales, and Xanthomonadales. In total, we detected nearly 9,000 gene cassettes, and found that many could be involved in plant growth promotion or phytopathogenicity, suggesting that integrons might play a role in bacterial mutualistic or pathogenic lifestyles. The rhizosphere was enriched in cassettes involved in the transport and metabolism of diverse substrates, suggesting that they may aid in adaptation to this environment, which is rich in root exudates. We also found that integrons facilitate cross-species HGT, which is particularly enhanced in the phyllosphere. This finding may provide an ideal opportunity to promote plant growth by fostering the spread of genes cassettes relevant to leaf health. Together, our findings suggest that integrons are important elements in plant microbiomes that drive HGT, and have the potential to facilitate plant host adaptation.