Plant Pathology Research Articles

Transcriptome profiling reveals insight into the cold response of perennial ryegrass genotypes with contrasting freezing tolerance

Low freezing tolerance threatens the survival and productivity of perennial ryegrass under northern climate. In this study, we aimed to identify transcriptional changes in plants subjected to low and freezing temperatures as well as to elucidate differences between tolerant and sensitive genotypes. Response to freezing stress was evaluated in a panel of 160 perennial ryegrass genotypes by measuring electrolyte leakage after exposure to -12 °C and -14 °C for 24 h. Two tolerant and two sensitive genotypes were selected for the transcriptome analysis. Crown tissue samples were collected at six treatments: before the start of cold acclimation (control point), at the start of acclimation, after one week of acclimation, after three weeks of acclimation, after freezing at -5 °C and freezing at -10 °C. A total of 11,125 differentially expressed genes (DEGs) were identified in the sensitive and 12,937 DEGs in the tolerant genotypes, when comparing the control vs. each of the acclimation and freezing treatments, as well as the end of acclimation vs. freezing treatments. Among the identified DEGs 3323 were unique to the sensitive genotypes, 5135 were unique to the tolerant genotypes and 7802 were shared. Genes upregulated during cold acclimation and freezing stress were linked to the MAPK signalling pathway, circadian rhythm, starch and sucrose metabolism, plant-pathogen interaction, carbon fixation, alpha-linoleic acid metabolism, carotenoid metabolism, glyoxylate and dicarboxylate metabolism pathways. Downregulated genes were linked to ATP-dependent chromatin remodelling, fatty acid elongation and DNA replication. The downregulation of fatty acid elongation and glutathione metabolism DEGs could indicate that the studied genotypes respond to cold stress in a novel or not yet well-characterized manner.

Re-Envisioning the Plant Disease Triangle: Full Integration of the Host Microbiota and a Focal Pivot to Health Outcomes.

The disease triangle is a structurally simple but conceptually rich model that is used in plant pathology and other fields of study to explain infectious disease as an outcome of the three-way relationship between a host, a pathogen, and their environment. It also serves as a guide for finding solutions to treat, predict, and prevent such diseases. With the omics-driven, evidence-based realization that the abundance and activity of a pathogen are impacted by proximity to and interaction with a diverse multitude of other microorganisms colonizing the same host, the disease triangle evolved into a tetrahedron shape, which features an added fourth dimension representing the host-associated microbiota. Another variant of the disease triangle emerged from the recently formulated pathobiome paradigm, which deviates from the classical "one pathogen" etiology of infectious disease in favor of a scenario in which disease represents a conditional outcome of complex interactions between and among a host, its microbiota (including microbes with pathogenic potential), and the environment. The result is a version of the original disease triangle where "pathogen" is substituted with "microbiota." Here, as part of a careful and concise review of the origin, history, and usage of the disease triangle, I propose a next step in its evolution, which is to replace the word "disease" in the center of the host-microbiota-environment triad with the word "health." This triangle highlights health as a desirable outcome (rather than disease as an unwanted state) and as an emergent property of host-microbiota-environment interactions. Applied to the discipline of plant pathology, the health triangle offers an expanded range of targets and approaches for the diagnosis, prediction, restoration, and maintenance of plant health outcomes. Its applications are not restricted to infectious diseases only, and its underlying framework is more inclusive of all microbial contributions to plant well-being, including those by mycorrhizal fungi and nitrogen-fixing bacteria, for which there never was a proper place in the plant disease triangle. The plant health triangle also may have an edge as an education and communication tool to convey and stress the importance of healthy plants and their associated microbiota to a broader public and stakeholdership.

Integration of Transcriptomics and WGCNA to Characterize Trichoderma harzianum-Induced Systemic Resistance in Astragalus mongholicus for Defense against Fusarium solani.

Beneficial fungi of the genus Trichoderma are among the most widespread biocontrol agents that induce a plant's defense response against pathogens. Fusarium solani is one of the main pathogens that can negatively affect Astragalus mongholicus production and quality. To investigate the impact of Trichoderma harzianum on Astragalus mongholicus defense responses to Fusarium solani, A. mongholicus roots under T. harzianum + F. solani (T + F) treatment and F. solani (F) treatment were sampled and subjected to transcriptomic analysis. A differential expression analysis revealed that 6361 differentially expressed genes (DEGs) responded to T. harzianum induction. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the 6361 DEGs revealed that the genes significantly clustered into resistance-related pathways, such as the plant-pathogen interaction pathway, phenylpropanoid biosynthesis pathway, flavonoid biosynthesis pathway, isoflavonoid biosynthesis pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and plant hormone signal transduction pathway. Pathway analysis revealed that the PR1, formononetin biosynthesis, biochanin A biosynthesis, and CHIB, ROS production, and HSP90 may be upregulated by T. harzianum and play important roles in disease resistance. Our study further revealed that the H2O2 content was significantly increased by T. harzianum induction. Formononetin and biochanin A had the potential to suppress F. solani. Weighted gene coexpression network analysis (WGCNA) revealed one module, including 58 DEGs associated with T. harzianum induction. One core hub gene, RPS25, was found to be upregulated by T. harzianum, SA (salicylic acid) and ETH (ethephon). Overall, our data indicate that T. harzianum can induce induced systemic resistance (ISR) and systemic acquired resistance (SAR) in A. mongholicus. The results of this study lay a foundation for a further understanding of the molecular mechanism by which T. harzianum induces resistance in A. mongholicus.

RNA-Seq and WGCNA Analyses Reveal Key Regulatory Modules and Genes for Salt Tolerance in Cotton.

The problem of soil salinization has seriously hindered agricultural development. Cotton is a pioneering salinity-tolerant crop, so harvesting its key salinity-tolerant genes is important for improving crop salt tolerance. In this study, we analyzed changes in the transcriptome expression profiles of the salt-tolerant cultivar Lu Mian 28 (LM) and the salt-sensitive cultivar Zhong Mian Suo 12 (ZMS) after applying salt stress, and we constructed weighted gene co-expression networks (WGCNA). The results indicated that photosynthesis, amino acid biosynthesis, membrane lipid remodeling, autophagy, and ROS scavenging are key pathways in the salt stress response. Plant-pathogen interactions, plant hormone signal transduction, the mitogen-activated protein kinase (MAPK) signaling pathway, and carotenoid biosynthesis are the regulatory networks associated with these metabolic pathways that confer cotton salt tolerance. The gene-weighted co-expression network was used to screen four modules closely related to traits, identifying 114 transcription factors, including WRKYs, ERFs, NACs, bHLHs, bZIPs, and MYBs, and 11 hub genes. This study provides a reference for acquiring salt-tolerant cotton and abundant genetic resources for molecular breeding.

Roadmap to Success: How Oomycete Plant Pathogens Invade Tissues and Deliver Effectors.

Filamentous plant pathogens threaten global food security and ecosystem resilience. In recent decades, significant strides have been made in deciphering the molecular basis of plant-pathogen interactions, especially the interplay between pathogens' molecular weaponry and hosts' defense machinery. Stemming from interdisciplinary investigations into the infection cell biology of filamentous plant pathogens, recent breakthrough discoveries have provided a new impetus to the field. These advances include the biophysical characterization of a novel invasion mechanism (i.e., naifu invasion) and the unraveling of novel effector secretion routes. On the plant side, progress includes the identification of components of cellular networks involved in the uptake of intracellular effectors. This exciting body of research underscores the pivotal role of logistics management by the pathogen throughout the infection cycle, encompassing the precolonization stages up to tissue invasion. More insight into these logistics opens new avenues for developing environmentally friendly crop protection strategies in an era marked by an imperative to reduce the use of agrochemicals.

Efficacy of Different Fungicides against Leaf Blight of Carrot Caused by Alternaria alternata (Fr.) Keissler

Background: Leaf blight disease is painful nerve to carrot growing farmer because it causes huge economic loss to the farmer every year. Leaf blight of carrot is seed and soil borne disease causes by Alternaria alternata. Hence management of the disease by fungicides is the best alternative. Therefore, in the present investigation, our main emphasis was to identify best fungicide for management of leaf blight of carrot. Methods: Seven fungicides were tested against leaf blight pathogen (Alternaria alternata) in lab as well as in cage house condition. The experiment was conducted at Cage house of department of Plant Pathology, COA, Jodhpur during Rabi-2020-21. Result: Among all the fungicides used in the present investigation, difenoconazole 25% inhibited the 100% mycelial growth at all the concentrations. The next best treatment was tebuconazole 50%+trifloxystrobin 25% inhibited the 99.02% mycelial growth and Minimum mycelial growth inhibition was observed in mancozeb 75% WP followed by carbendazim 12%+mancozeb 63% 61.58% and 77.70%, respectively; along with control plate was showed 100% mycelium growth. The superior treatments under in vitro carry forward in vivo condition. When applied as foliar application under cage house condition, difenoconazole 25 EC at 0.25 ml/lit (11.17%) was observed lowest disease incidence.

Effect of different weight initialization strategies on transfer learning for plant disease detection

AbstractThe weight initialization technique for transfer learning refers to the practice of using pretrained models that can be modified to solve new problems, instead of starting the training process from scratch. In this study, six different transfer learning weight initialization strategies were proposed for plant disease detection: scratch (i.e., random initialization), pretrained model on cross‐domain (ImageNet), model trained on related domain (ISIC 2019), model trained on related domain (ISIC 2019) with cross‐domain (ImageNet) weights, model trained on same domain (PlantVillage), and model trained on same domain (PlantVillage) with cross‐domain weights (ImageNet). Weights from each strategy were transferred to a target dataset (Plant Pathology 2021). These strategies were implemented using eight deep learning architectures. It was observed that transferring from any strategy led to an average acceleration of convergence ranging from 33.88% to 73.16% in mean loss and an improvement of 8.72%–42.12% in mean F1‐score compared to the scratch strategy. Moreover, although smaller and less comprehensive than ImageNet, transferring information from the same domain or related domain proved to be competitive compared to transferring from ImageNet. This indicates that ImageNet, which is widely favoured in the literature, may not necessarily represent the most optimal transfer source for the given context. In addition, to identify which strategies have significant differences, a post hoc analysis using Tukey's HSD test was conducted. Finally, the classifications made by the proposed models were visualized using Grad‐CAM to provide a qualitative understanding of how different weight initialization strategies affect the focus areas of the models.

Chemical control of Alternaria and Corynespora leaf spot complex in Bt cotton

Cotton is an important cash crop of India as well as Gujarat, enjoying the pre-eminent status as 'White gold' and 'King of Fibres'. Cotton is widely affected by many diseases including Alternaria leaf spot and target spot or Corynespora leaf spot caused by Alternaria alternata and Corynespora cassiicola, respectively. The main objective of the study was to investigate the effectiveness of fungicides against leaf spot complex (Alternaria leaf spot and target spot) of Bt cotton. The field experiment was conducted during Kharif 2022 at Plant Pathological Research Farm, Department of Plant Pathology, BA College of Agriculture, Anand Agricultural University Anand, Gujarat. Fungicides were applied two times at 15 days interval after initiation of disease and results showed that among the tested treatments including control, Azoxystrobin 18.2% + Difenoconazole 11.4% SC recorded significantly lowest disease intensity (18.50% and 17.92%) as compared to control (50.75% and 46.85%), with highest disease control (63.54% and 61.73%) for Alternaria leaf spot and target spot respectively. The highest yield (1968 kg ha ) and ICBR (1:10.62) was -1 recorded in Azoxystrobin 18.2% + Difenoconazole 11.4% SC. The next best treatment found in terms of disease control was Tebuconazole 50% + Trifloxystrobin 25% WG. So in nutshell it was found that readymix fungicides were found best and also cost effective in managing both the diseases.. KEYWORDS :Alternaria alternata, Corynespora cassiicola, leaf spot, fungicides

Wild mungbean resistance to the nematode Meloidogyne enterolobii involves the induction of phenylpropanoid metabolism and lignification.

Root-knot nematodes (Meloidogyne spp.) are plant parasites causing annual economic losses amounting to several billion US dollars worldwide. One of the most aggressive species is M. enterolobii, a growing threat to agriculture due to its broad host range and ability to overcome many known resistance genes. Mungbean, a nutritionally and economically valuable crop, is particularly vulnerable to nematodes and pathogens. However, research focusing on mungbean resistance to M. enterolobii is scarce, and the corresponding defense mechanisms are poorly understood. Here, we screened mungbean accessions and identified an accession strongly resistant to M. enterolobii. Transcriptome analysis revealed 2730 differentially expressed genes (DEGs) in this resistant accession (CPI106939) compared to 1777 in the susceptible accession (Crystal) 7 days after nematode inoculation. The gene ontology (GO) upregulated in CPI106939 with functions related to plant-pathogen interactions, plant hormone signaling, oxidative stress, and plant immunity. Plant defense-related genes (WRKY, PAL, MAPK, POD and PR) were also significantly induced in CPI106939. Metabolome analysis showed that four secondary metabolites related to phenylpropanoid metabolism and lignification were significantly enriched in CPI106939. The induced immune response and secondary metabolites may underpin the enhanced resistance to M. enterolobii, providing insight into the resistance mechanisms in accession CPI106939 as well as candidate genes controlling the interaction between mungbean and its nematode parasite. Our study therefore provides foundations for the breeding of new varieties with intrinsic M. enterolobii resistance.

Status of Alternaria leaf blight in cotton and its fungicidal management

Surveys were carried out in the three districts of North Gujarat, viz., Aravalli, Sabarkantha, and Banaskantha to investigate the severity of Alternaria leaf blight in cotton, The disease was found to be quite severe and with a mean PDI of 23.77, the Banaskantha district had the highest disease intensity of Alternaria leaf spot disease; in contrast, the average disease intensity in the Aravalli and Sabarkantha districts was 17.94 and 20.44 per cent, respectively. Further, to manage the disease, research was conducted to evaluate the in vitro and in planta bioefficacy of fungicides against Alternaria macrospora of cotton at the Department of Plant Pathology and Alternaria leaf blight in cotton at Agronomy Instructional farm, S D Agricultural University Sardarkrushinagar, Gujarat, respectively. Under in vitro condition, among five systemic fungicides, Carbendazim showed the highest per cent growth inhibition, while Propiconazole showed the lowest. Among different non-systemic fungicides, Mancozeb inhibited the radial growth of A. macrospora the most, while Chlorothalonil inhibited the least. Further, among five combined fungicides, Tebuconazole 50% + Trifloxistrobin 25 WG inhibited the most growth and Captan 70% + Hexaconazole 50 WP inhibited the least. Thereafter, the bio-efficacy of the two most effective fungicides from each group (two systemic, two non-systemic, and two combined fungicides) was tested under field conditions, and the mean disease intensity ranged from 12.28 to 36.43 per cent, with the lowest being Tebuconazole 50% + Trifloxystrobin 25 WG and the highest being untreated control. The highest percentage of illness control (66.29%).. KEYWORDS :Alternaria macrospora, cotton, fungicides

Effect of Tulsi Leaf Powder along with Casing Mixture on the Growth Parameters and Yield of White Button Mushroom [Agaricus bisporus (Lange) Imbach

Agaricus bisporus (Lange) Imbach commonly known as white button mushroom, is the most widely accepted food globally with nutritional and medicinal properties. The present experiment was conducted during the Rabi season 2023 - 2024 at Mushroom crop room, Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh to evaluate the effect of tulsi leaf powder at different concentrations (1 %, 1.5 %, 2 %, 2.5 % and 3 %) incorporated into casing mixture (alone and combination) viz., farm yard manure, farm yard manure + cocopeat + sawdust (1:1:1) with an objective to monitor the growth and yield aspects of white button mushroom. Among all treatments used in the study, the results revealed that minimum average time taken for completion of case run (15.14 days) and pinhead initiation (15.57 days) as well as maximum pileus diameter (4.63 cm), stalk length (3.77 cm), stalk diameter (3.01 cm), maximum yield (557.9 g), biological efficiency(12.97 %) and highest cost benfit ratio (1: 3.18) was recorded in farm yard manure + cocopeat + sawdust (1:1:1) + tulsi leaf powder @ 3%. These results indicated that incorporating tulsi leaf powder @3% in casing mixture improves the growth and yield of A. bisporus.

Using Transcriptomics to Determine the Mechanism for the Resistance to Fusarium Head Blight of a Wheat-Th. elongatum Translocation Line.

Fusarium head blight (FHB), caused by the Fusarium graminearum species complex, is a destructive disease in wheat worldwide. The lack of FHB-resistant germplasm is a barrier in wheat breeding for resistance to FHB. Thinopyrum elongatum is an important relative that has been successfully used for the genetic improvement of wheat. In this study, a translocation line, YNM158, with the YM158 genetic background carrying a fragment of diploid Th. elongatum 7EL chromosome created using 60Co-γ radiation, showed high resistance to FHB under both field and greenhouse conditions. Transcriptome analysis confirmed that the horizontal transfer gene, encoding glutathione S-transferase (GST), is an important contributor to FHB resistance in the pathogen infection stage, whereas the 7EL chromosome fragment carries other genes regulated by F. graminearum during the colonization stage. Introgression of the 7EL fragment affected the expression of wheat genes that were enriched in resistance pathways, including the phosphatidylinositol signaling system, protein processing in the endoplasmic reticulum, plant-pathogen interaction, and the mitogen-activated protein kinase (MAPK) signaling pathway at different stages after F. graminearium infection. This study provides a novel germplasm for wheat resistance to FHB and new insights into the molecular mechanisms of wheat resistance to FHB.

Phytotoxic effect of Carica papaya extract on seed-borne fungus of African Yam Bean (Sphenostylis stenocarpa Hochst ex. A. Rich. Harms) seeds

Extracts of many higher plants have been reported to exhibit antifungal properties under laboratory experiments. This study was therefore carried out to investigate the effect of Carica papaya plant extracts on the African Yam Bean seed-borne pathogen. The seed health test of African Yam Bean was carried out using the blotter paper method. The experiment was conducted at the Plant Pathology Laboratory of the Department of Crop Science and Horticulture, Nnamdi Azikiwe University, Awka. Test of plant extract for inhibition of radial growth of seed-borne pathogen of African yam bean was studied under in vitro experiment at 0%, 50%, 75% and 100% concentrations with 0% as the control. The design was a Completely Randomized Design (CRD) with three replications. The test plant extracts of different concentrations were added into Petri dishes containing molten-sterilized Sabouraud Dextrose Agar (SDA) and swayed gently on the laboratory bench to allow an even mixture These were allowed to gel. Then nine millimeter discs of a seven-day pure culture of Aspergillus flavus were aseptically placed on the centre of the Petri dishes containing the SDA-extract mixture. Records on the radial inhibition effect of the test plant extract were kept for further analysis. Data on radial inhibition of fungus were subjected to Analysis of Variance (ANOVA). Results showed that Aspergillus niger, Aspergillus flavus and Aspergillus terreus were isolated from incubated African Yam Bean seeds. Carica papaya leaf extract used was very effective and the higher the concentrations of extract, the more effective in the inhibition of radial growth of the test fungus. It could therefore be recommended that farmers should always conduct viability tests on procured seeds before planting. Farmers should rather use plant extract such as the one used in this experiment in controlling seed-borne fungal pathogens of African Yam Bean seeds than synthetic fungicides.

A cold-inducible MYB like transcription factor, CsHHO2, positively regulates chilling tolerance of cucumber fruit by enhancing CsGR-RBP3 expression

Plant HRS1 (hypersensitive to low phosphate (Pi)-elicited primary root shortening 1) and its homologs have been primarily characterized in Pi and nitrogen responses. However, their regulatory roles in cold responses remain largely unexplored. Here, we characterized the functional roles of HRS1 homolog 2 (CsHHO2) in regulating cold resistance in harvested cucumber fruit and examined the dependency of the role on glycine-rich RNA-binding protein 3 (CsGR-RBP3) gene expression. Cold treatments strongly induced CsHHO2 expression in cucumber fruit. GUS staining and expression analysis revealed that cold treatment stimulated CsHHO2 expression, at least partially, by enhancing the promoter activity. Subcellular localization results indicated that the green fluorescent protein (GFP)-tagged CsHHO2 proteins were localized to both the nucleus and the cytoplasm (potentially the plasma membrane), with confirmed nuclear localization when co-overexpressed with mCherry. Reducing CsHHO2 expression in cucumber fruit through VIGS significantly compromised the chilling tolerance, while its overexpression in cucumber fruit and Arabidopsis plants enhanced cold tolerance. The results of electrophoretic mobility shift assay (EMSA), yeast one-hybrid (Y1H) assay and dual-luciferase reporter (DLR) assay indicated that CsHHO2 specifically bound to the promoter of CsGR-RBP3, and enhanced its transcription. Transcriptomic analysis indicated that most differentially expressed genes (DEGs) modulated by CsHHO2 and CsGR-RBP3 proteins were identical, and the common DEGs were mainly enriched in several stress defense pathways, such as plant-pathogen interaction, phenylpropanoid biosynthesis, and plant hormone signal transduction. Functional complementation analysis of CsHHO2 and CsGR-RBP3 in cucumber fruit revealed that CsGR-RBP3 expression were indispensable for CsHHO2-modulated cold resistance. These results collectively suggest that CsHHO2, activated by cold signals, positively regulates the chilling tolerance of cucumber fruit by enhancing CsGR-RBP3 expression. Overall, this work suggests CsHHO2 as a key regulator of cold tolerance in cucumber fruit, provides key genetic resources for breeding cold-resistant cucumbers, and sheds novel insight into the roles of HRS1 family members in regulating plant development under environmental stresses.

Transcriptome analysis of maize resistance to Fusarium verticillioides

ABSTRACT Maize (Zea mays) is a crucial crop for both food and economic purposes. Fusarium verticillioides is known to cause ear rot in corn, leading to a reduction in corn yield. Understanding the regulatory network of maize resistance to this ear rot is crucial for identifying key genes associated with disease resistance. The study revealed that inbred line J1259 exhibited resistance to Fusarium verticillioides by increasing the activities of POD and CAT enzymes. Transcriptome analysis at 48 and 96 hours post-infection with Fusarium verticillioides revealed a large number of DEGs involved in plant-pathogen interactions, MAPK signaling pathways-plants and plant hormone signaling were significant up-regulated. Additionally, transcription factors related to hormone signaling, particularly the ARF family involved in auxin regulation, were enriched. These results lay a foundation for further investigations into the mechanisms underlying the disease resistance response of J1259.

Citrus tristeza virus: A century‐long challenge for the world's citrus industries

AbstractCitrus tristeza virus (CTV) is a causal agent of diseases that have challenged the global citrus production for more than a century. The disease named ‘tristeza’, which means ‘sadness’ in Portuguese and Spanish, has spread by aphids and vegetative propagation, resulting in costly pandemics that reshaped the world citrus production by forcing the adaption of disease‐tolerant rootstocks. Furthermore, management of the second major CTV‐induced disease, stem pitting, became a unique example of the use of cross‐protection on a large nationwide scale, allowing many citrus growing regions to control the disease that could not be managed through horticultural practices. The information gathered in this review commemorates a hundred years of research on the virus and the respective diseases, which began with classical horticultural approaches and advanced toward the cutting‐edge molecular biology studies. In this regard, it is proper to mention that CTV research greatly benefited from close international collaboration between research institutions and scientists from the affected and nonaffected citrus areas. Moreover, despite the considerable initial losses caused by tristeza, the world's fresh fruit and juice concentrate citrus industries reemerged as highly productive following the research advancements, a situation that changed throughout Florida and Brazil in the past two decades or so with the outbreak of the devastating citrus greening (Huanglongbing) bacterial disease. This review encompasses past and recent advances in the CTV research positioning the citrus‐CTV pathosystem as a pivotal model system for investigating virus interactions with perennial woody hosts. The review will also serve as an updated version of the respective section on CTV in the Description of Plant Viruses that the Association of Applied Biologists manages. We dedicated this review to the 85th Birthday celebration of Prof. Moshe Bar‐Joseph, a world‐renowned plant pathologist whose half‐a‐century‐long career devoted to citrus diseases yielded many important, pioneering discoveries on CTV and other closteroviruses. Many of those are highlighted in this review. Prof. Bar‐Joseph retired from the Volcani Center, Agricultural Research Organization in Israel several years ago, yet he continues to be actively engaged in research and provides his expertise to citrus pathologists around the world in the present days.

Tandem mass tag (TMT)-based quantitative proteomics analysis reveals the different responses of contrasting alfalfa varieties to drought stress

BackgroundDrought stress restricts the growth, distribution and productivity of alfalfa (Medicago sativa L.). In order to study the response differences of alfalfa cultivars to drought stress, we previously carried out physiological and molecular comparative analysis on two alfalfa varieties with contrasting drought resistance (relatively drought-tolerant Longdong and drought-sensitive Algonquin). However, the differences in proteomic factors of the two varieties in response to drought stress still need to be further studied. Therefore, TMT-based quantitative proteomic analysis was performed using leaf tissues of the two alfalfa cultivars to identify and uncover differentially abundant proteins (DAPs).ResultsIn total, 677 DAPs were identified in Algonquin and 277 in Longdong under drought stress. Subsequently, we conducted various bioinformatics analysis on these DAPs, including subcellular location, functional classification and biological pathway enrichment. The first two main COG functional categories of DAPs in both alfalfa varieties after drought stress were ‘Translation, ribosomal structure and biogenesis’ and ‘Posttranslational modification, protein turnover, chaperones’. According to KEGG database, the DAPs of the two alfalfa cultivars after drought treatment were differentially enriched in different biological pathways. The DAPs from Algonquin were enriched in ‘photosynthesis’ and ‘ribosome’. The pathways of ‘linoleic acid metabolism’, ‘protein processing in endoplasmic reticulum’ and ‘RNA transport’ in Longdong were significantly enriched. Finally, we found significant differences in DAP enrichment and expression patterns between Longdong and Algonquin in glycolysis/glycogenesis, TCA cycle, photosynthesis, protein biosynthesis, flavonoid and isoflavonoid biosynthesis, and plant-pathogen interaction pathway after drought treatment.ConclusionsThe differences of DAPs involved in various metabolic pathways may explain the differences in the resistance of the two varieties to drought stress. These DAPs can be used as candidate proteins for molecular breeding of alfalfa to cultivate new germplasm with more drought tolerance to adapt to unfavorable environments.

Influence of a New Generation Fungicide on Fusarium Head Blight in Spring Barley

Fusarium head blight is a serious problem in both traditional and intensive agriculture. The way to solve this problem is to use combined systemic fungicides. We therefore studied the effect of the new-generation fungicides Alto Super and KE (Propiconazole 250 g/l and Ciproconazole 80 g/l) combined with the foliar fertilizer Ultramag Super Sulphur-900. Laboratory studies were carried out at the Plant Pathology Laboratory of the People's Friendship University of Russia (RUDN), and field experiments were carried out in 2022 at the experimental field station of the Federal Research Centre "Nemchinovka." Fusarium head blight appeared in late July and early August. The application of the new-generation fungicide Alto Super, KE, alone and in combination with the new foliar fertilizer Ultramag Super Sulphur considerably reduced the development of the epiphytotic fungal disease. Their biological efficacy was 44.53–83.36%. The yield of Nur Spring barley in the experimental variants was higher than in the control variant. The yield gain of spring barley increased by 5.85% for Alto Super, KE, 9.40% for Ultramag Super Sulphur-900, and 12.85% for Alto Super, KE, and Ultramag Super Sulphur-900.

'Candidatus Phytoplasma vignae', assigning a species description to a long-known phytoplasma occurring in northern Australia.

Gene- and genome-based approaches were used to determine whether Vigna little leaf (ViLL) phytoplasma, which occurs in northern Australia, is a distinct 'Candidatus Phytoplasma' species. The ViLL 16S rRNA gene sequences exhibited the highest known similarity to species in the 16SrXXIX-A and 16SrIX-D subgroups, namely 'Candidatus Phytoplasma omanense' (98.03-98.10%) and 'Candidatus Phytoplasma phoenicium' (96.87-97.20%), respectively. A total of 48 single-copy orthologue genes were identified to be shared among the two draft ViLL phytoplasma genomes, 30 publicly available phytoplasma genomes, and one Acholeplasma laidlawii genome as the outgroup taxon. Phylogenomic assessments using the 48 shared single-copy orthologue genes supported that ViLL and 'Ca. Phytoplasma phoenicium' were closely related yet distinct species. The 16S rRNA gene sequence analysis and phylogenomic assessment indicate that ViLL phytoplasmas are a distinct taxon. As such, a novel species, 'Candidatus Phytoplasma vignae', is proposed. Strain BAWM-336 (genome accession number JAUZLI000000000) detected in Momordica charantia (bitter melon) serves as the reference strain of this species, with infected plant material deposited in the Victorian Plant Pathology Herbarium (VPRI) as VPRI 44369.

Untargeted metabolomic analysis reveals a potential role of saponins in the partial resistance of pea (Pisum sativum) against a root rot pathogen, Aphanomyces euteiches.

In soil-borne diseases, the plant-pathogen interaction begins as soon as the seed germinates and develops into a seedling. Aphanomyces euteiches, an oomycete, stays dormant in soil and gets activated by sensing the host through chemical signals present in the root exudates. The composition of plant exudates may, thus, play an important role during the early phase of infection. To better understand the role of root exudates in plant resistance, we investigated the interaction between partially resistant lines (PI660736 and PI557500) and susceptible pea cultivars (CDC Meadow and AAC Chrome) against Aphanomyces euteiches during the pre-invasion phase. The root exudates of two sets of cultivars clearly distinguished from each other in inducing oospore germination. PI557500 root exudate not only had diminished induction but also inhibited the oospore germination. The contrast between the root exudates of resistance and susceptible cultivars was reflected in their metabolic profiles. Data from fractionation and oospore germination inhibitory experiments identified a group of saponins that accumulated differentially in susceptible and resistant cultivars. We detected 56 saponins and quantified 44 of them in pea root and 30 from root exudate; the majority of them, especially Soyasaponin I and dehydrosoyasaponin I with potent in vitro inhibitory activities, were present in significantly higher amounts in both roots and root exudates of PI660736 and PI557500 as compared to Meadow and Chrome. Our results provide evidence for saponins as deterrents against Aphanomyces euteiches, which might have contributed to the resistance against root rot in the studied pea cultivars.