Search Results (49)

In the Campania region of southern Italy, a formerly undescribed witches’-broom disease of cultivated strawberry characterized by symptoms similar to those of strawberry witches’-broom and multiplier diseases occurring in North America, has been observed. Strawberry witches’-broom and multiplier diseases are not known to occur in Europe. To elucidate the etiology of the new strawberry disease occurring in southern Italy and to determine the taxonomic position of the presumable causal agent, field observations and PCR assays using universal and group-specific phytoplasma primers followed by multigene sequence analysis were carried out. All of the symptomatic strawberry plants examined tested phytoplasma positive with universal primers and primers specific to the elm yellows (EY) phytoplasma group or 16SrV group. The percentage of diseased plants in the fields was about 30%. Data obtained from sequence and phylogenetic and virtual RFLP analyses of PCR-amplified rDNA (16S rDNA and 16S/23S rDNA spacer region), rpsV (rpl22) and rpsC (rps3), map, imp and groEL gene sequences, showed that the diseased strawberry plants harbored phytoplasma strains which were identical or nearly identical to each other and to strains of the rubus stunt (RuS) agent ‘Ca. Phytoplasma rubi’, a member of the 16SrV group, subgroup 16SrV-E. The 16S rDNA sequence similarity among the strawberry-infecting phytoplasma strains ranged from 99.1 to 99.9%. These strains shared the same range of 16S rDNA sequence similarity with RuS phytoplasma strains including the reference strain RUS of ‘Ca. Phytoplasma rubi’. This is the first report on the occurrence of RuS phytoplasma in naturally affected strawberry plants. Full article

Witches’ broom disease of blue palo verde (Parkinsonia florida) was reported more than sixty years ago. Characteristic symptoms consist of dense clusters of shortened, brittle branches and stunted leaves. The suspect causal agent has been identified as palo verde broom virus (PVBV), genus, Emaravirus, family, Fimoviridae. Here, the first complete PVBV genome sequence was determined, and virus small interfering RNAs (vsiRNAs), primary metabolites, and phytohormone profiles were characterized from infected palo verde leaves, adventitious shoots, flowers, and seeds. Based on pairwise distances, PVBV RNAs 1–4 shared 54–65% nucleotide identity and 19–51% amino acid similarity, respectively, with other emaraviruses, while PVBV RNA 5 shared no sequence homology with any emaravirus. The 21–24-nt virus-derived vsiRNAs, indicative of post-transcriptional gene silencing (PTGS), represented nearly the entire PVBV genome in flowers, leaves, seeds, and adventitious shoots; however, PVBV RNA 3 and RNA 4 were most heavily targeted in all plant parts. Evidence that six major phytohormones were altered in PVBV-infected compared to virus-free trees indicated that emaravirus-infected trees mount classical defense responses to virus infection and/or eriophyid mite infestations. Detection of PVBV RNA genome segments 1–5, accumulation of predominantly 21-nt vsiRNAs, homologous to the PVBV genome and transcripts, and altered levels of phytohormones and metabolites in PVBV-infected trees strongly implicate PVBV as the causal agent of witches’ broom disease. Full article

Moniliophthora roreri (MR, frosty pod rot) and M. perniciosa (MP, witches’ broom disease) pose critical threats to cacao production in Latin America. This study explores the biocontrol potential of Trichoderma spp. strains against these pathogens through exploratory analysis of mycoparasitism, chitinolytic activity, and volatile organic compound (VOC) production. Dual-culture assays revealed species-specific antagonism, but C2A/C4B showed a dual-pathogen efficacy (>93% of Monioliopthora inhibition). Chitinase activity revealed C4A/C1 strains as exceptional producers (72 mg/mL NAGA vs. MR and 94 mg/mL vs. MP, respectively). GC-MS analysis identified pathogen-modulated VOC dynamics: hexadecanoic acid dominated in 80% Trichoderma solo-cultures (up to 26.65% peak area in C3B). MP showed 18.4-fold higher abundance of hexadecanoic acid than MR (0.23%). In 90% of dual-culture with MR and MP, HDA was detected as the most abundant. Functional specialization was evident. C4A and C1 prioritized chitinase production growing on MR and MP cell walls (respectively), whereas C9 excelled in antifungal hexadecanoic acid synthesis in confrontation with both pathogens. Complementary strengths among strains—enzymatic activity in C4A/C4B versus volatile-mediated inhibition in C9—suggest niche partitioning, supporting a consortium-based approach for robust biocontrol. This study provides preliminary evidence for the biocontrol potential of several Trichoderma strains, showing possible complementary modes of action. Full article

Evidence from an increasing number of studies indicates that plant endophytic microorganisms play a significant role during biotic and abiotic stress resistance. To date, however, only a handful of studies on endophytes in response to the presence of phytoplasmas have been conducted. The production of jujube (Ziziphus jujuba) is threatened by jujube witches’ broom (JWB) disease, which is associated with the presence of the JWB phytoplasma ‘Candidatus Phytoplasma ziziphi’. To investigate the impact of jujube witches’ broom phytoplasma on the endophyte populations in jujube, high-throughput sequencing was performed in healthy and JWB-infected orchard jujube trees and in vitro jujube shoots. The results showed that the presence of JWB phytoplasma in jujube altered the abundance, diversity, and community structure of endophytic bacteria and fungi. In the branches and the roots, the presence of JWB phytoplasma was associated with an increase in the richness of the endophytic communities and a decrease in their diversity, with the phyla Proteobacteria, Firmicutes, and Bacteroidota and the genus ‘Ca. Phytoplasma’ becoming the most abundant. The presence of phytoplasmas was also associated with the remodeling of the endophytic microorganisms’ interaction network, shifting to a simpler biodiversity state. These results demonstrate the response of the jujube endophytic community to the presence of JWB phytoplasmas and shed light on the possible antagonistic agents that could be further evaluated for JWB disease biocontrol. Full article

Jujube witches’ broom (JWB) disease, caused by Candidatus Phytoplasma ziziphi (Ca. P. ziziphi), severely threatens the production of Chinese jujube (Ziziphus jujuba Mill.). Emerging evidence highlights the critical role of phytoplasma-secreted effectors in pathogenesis, though few have been functionally characterized. Here, we identified a Sec-dependent effector, JWB790, from Ca. P. ziziphi, which was shown to suppress plant immunity. Through transient expression assays in Nicotiana benthamiana, pathogen inoculation assays, the generation of transgenic Arabidopsis thaliana plants, and RNA-seq-based transcriptomic profiling, we systematically investigated the virulence function of JWB790. Our findings revealed that JWB790 is highly expressed in JWB-infected tissues. The transient expression of JWB790 in N. benthamiana suppressed BAX-induced cell death and H₂O₂ accumulation. Furthermore, the stable overexpression of JWB790 in A. thaliana compromised disease resistance, accompanied by reduced H₂O₂ accumulation and callose deposition triggered by flg22. Additionally, the RNA-seq analysis of JWB790 transgenic Arabidopsis plants indicated that the overexpression of JWB790 altered the expression of biotic stress-related genes. In summary, JWB790 is a virulence factor that suppresses plant immunity and promotes pathogen proliferation. These results advance our understanding of Ca. P. ziziphi pathogenesis. Full article

The cultivation of jujube (Ziziphus jujuba) in China is threatened by jujube witches’ broom (JWB) disease, a devastating infectious disease associated with JWB phytoplasma (‘Candidatus Phytoplasma ziziphi’). In many plants, proteins in the Argonaute (AGO) family, as main components of the RNA-induced silencing complex (RISC), play important roles in RNA silencing and pathogen resistance. The jujube telomere-to-telomere genome was searched by BLAST using Arabidopsis AGOs as probes. A total of nine jujube AGO gene members were identified, with each containing the conserved N-terminal, PZA, and PIWI domains. Phylogenetic analysis revealed that the nine jujube AGOs scattered into all three Arabidopsis AGO clades. Expression patterns of the ZjAGO genes were analyzed in response to phytoplasma in transcriptome data and by qRT–PCR. The jujube–phytoplasma interaction altered the expression of jujube AGO genes. ZjAGO1 and ZjAGO8 were up-regulated in the majority of the eight sampling periods subjected to qRT–PCR analysis. In the transcriptome data, ZjAGO1 and ZjAGO8 were also up-regulated during the key stages 37 and 39 weeks after grafting (WAG) with phytoplasma-infected material. These two jujube Argonaute genes may play important roles in response to JWB phytoplasma infection. Full article

Moniliophthora perniciosa is one of the main pathogens affecting cocoa, and controlling it generally involves planting resistant genotypes followed by phytosanitary pruning. The identification of plant genes related to defense mechanisms is crucial to unravel the molecular basis of plant–pathogen interactions. Among the candidate genes, BiP stands out as a molecular chaperone located in the endoplasmic reticulum that facilitates protein folding and is induced under stress conditions, such as pathogen attacks. In this study, the SoyBiPD gene was expressed in Solanum lycopersicum plants and the plants were challenged with M. perniciosa. The control plants exhibited severe symptoms of witches’ broom disease, whereas the transgenic lines showed no or mild symptoms. Gel-free proteomics revealed significant changes in the protein profile associated with BiP overexpression. Inoculated transgenic plants had a higher abundance of resistance-related proteins, such as PR2, PR3, and PR10, along with increased activity of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase, and fungal cell wall-degrading enzymes (glucanases). Additionally, transgenic plants accumulated less H₂O₂, indicating more efficient control of reactive oxygen species (ROS). The interaction network analysis highlighted the activation of defense-associated signaling and metabolic pathways, conferring a state of defensive readiness even in the absence of pathogens. These results demonstrate that BiP overexpression increases the abundance of defense proteins, enhances antioxidant capacity, and confers greater tolerance to biotic stress. This study demonstrates the biotechnological potential of the BiP gene for genetic engineering crops with increased resistance to economically important diseases, such as witches’ broom in cocoa. Full article

Paulownia species not only have significant economic benefits but also show great potential in ecological conservation. However, they are highly susceptible to phytoplasma infections, causing Paulownia witches’ broom (PaWB), which severely restricts the development of the Paulownia industry. Salicylic acid (SA) plays a crucial role in plant disease resistance. However, there have been no reports on the effect of SA on PaWB. Due to the properties of SA, it may have potential in controlling PaWB. Based on the above speculation, the prevention and therapeutic effect of SA on PaWB and its effect on the PaWB-infected Paulownia transcriptome and proteome were studied in this work. The results indicated that 0.1 mmol/L was the optimal SA concentration for inhibiting the germination of Paulownia axillary buds. In terms of resistance physiological indicators, SA treatment significantly affected both Paulownia tomentosa infected (PTI) seedlings and Paulownia fortunei infected (PFI) seedlings, where the activities of peroxidase (POD) and superoxide dismutase (SOD) were enhanced. Malondialdehyde (MDA), O₂⁻, and H₂O₂, however, were significantly reduced. Specifically, after SA treatment, SOD activity increased by 28% in PFI and 25% in PTI, and POD activity significantly increased by 61% in PFI and 58% in PTI. Moreover, the MDA content decreased by 30% in PFI and 23% in PTI, the H₂O₂ content decreased by 26% in PFI and 19% in PTI, and the O₂⁻ content decreased by 21% in PFI and 19% in PTI. Transcriptomic analysis showed that there were significant upregulations of MYB, NAC, and bHLH and other transcription factors after SA treatment. Moreover, genes involved in PaWB-related defense responses such as RAX2 also showed significant differences. Furthermore, proteomic analysis indicated that after SA treatment, proteins involved in signal transduction, protein synthesis modification, and disease defense were differentially expressed. This work provides a research foundation for the prevention and treatment of PaWB and offers references for exploring anti-PaWB methods. Full article

Cassava witches’ broom disease (CWBD) is one of the most devastating diseases of cassava (Manihot esculenta Crantz), and it threatens global production of the crop. In 2017, a phytoplasma, Candidatus Phytoplasma luffae (Ca. P. luffae), was reported in the Philippines, and it has been considered as the causal agent, despite unknown etiology and transmission of CWBD. In this study, the nationwide occurrence of CWBD was assessed, and detection of CWBD’s pathogen was attempted using polymerase chain reaction (PCR) and next-generation sequencing (NGS) techniques. The results showed that CWBD has spread and become severe, exhibiting symptoms such as small leaf proliferation, shortened internodes, and vascular necrosis. PCR analysis revealed a low phytoplasma detection rate, possibly due to low titer, uneven distribution, or absence in the CWBD-symptomatic cassava. In addition, NGS techniques confirm the PCR results, revealing the absence or extremely low phytoplasma read counts, but a surprisingly high abundance of fastidious and xylem-limited fungus, Ceratobasidium sp. in CWBD-symptomatic plants. These findings cast doubt over the involvement of phytoplasma in CWBD and instead highlight the potential association of Ceratobasidium sp., strongly supporting the recent findings in mainland Southeast Asia. Further investigations are needed to verify the etiology of CWBD and identify infection mechanisms of Ceratobasidium sp. to develop effective diagnostic and control methods for disease management. Full article

This study examines the importance of cupuassu, a tropical fruit native to the Amazon, to Brazil’s biodiversity, the Amazon biome, and its potential for economic development. Cupuassu is a Non-Timber Forest Product and a fruit of the Theobroma genus, which also includes cocoa. Just in the state of Pará alone, cupuassu production in 2019 was over 4100 t with a gross value of 2.6 million USD produced. However, cupuassu cultivation still needs investment through technological advances to overcome threats such as witches’ broom disease and mycotoxin contamination. Cupuassu fruit is composed of pulp, seeds, and a shell; all these parts have a chemical composition with numerous bioactive compounds, especially the seeds, which also contain stimulant compounds, besides lipids and proteins. The processing of the whole cupuassu fruit has its economic value in the commercialization of the pulp, the extraction of cupuassu butter, and a product called Cupulate^®. However, in this process, the cake resulting from the oil pressing, often considered a waste product, has potential as a source of proteins, peptides, lipids, and bioactive molecules with functional and nutritional properties. Recycling this fruit processing waste can create high-value-added products for various industries and promote a circular economy. Full article

Mixed production systems play a vital role in the economic sustainability and ecological balance of agroecosystems. Cocoa and plantain are key crops in Ecuador but face phytosanitary challenges, like witches’ broom and black sigatoka diseases, especially when cultivated under monocropping systems. Combining habitat manipulation with adaptive pathogen management (APM) strategies can mitigate these challenges, but their efficacy in mixed cropping systems remains unclear. This study investigates disease and pest incidence in mixed cocoa–plantain systems during the establishment phase, focusing on the impact of spatial arrangements. Mixed agroecosystems showed a lower witches’ broom incidence in cocoa than monocultures. Whereas, in plantain, there was a consistent black sigatoka incidence across spatial arrangements but a lower infection rate per leaf within mixed systems. We found varied nematode populations with monocultures hosting the highest root damage due to phytoparasitic nematodes. Weevil populations were also influenced by spatial arrangements with monocultures among the highest. Overall, mixed agroecosystems influence disease and pest incidence, potentially hindering pathogen spread. Plantain–cocoa associations reduce disease incidence in cocoa but may not affect the overall incidence of black sigatoka in plantain, at least during the establishment phase. Continued monitoring is crucial for understanding the long-term impacts and microclimatic effects on pest populations that could offer sustainable pest management strategies, reducing the reliance on chemical pesticides. Full article

Tamarisk witches’ broom, yellowing, and little leaf symptoms were observed during 2018–2023 surveys of rural deserts in central regions of Iran with the highest disease incidence up to 72% in Chah Afzal (Yazd province). A verification of the presence and identity of phytoplasmas associated with these symptoms was then performed. Tamarisk tree branch cuttings obtained from symptomatic plants sprouted up to 90.3% but with 15–25 days’ delay compared to the asymptomatic ones and showed internode shortening and witches’ broom, while the branch cuttings from asymptomatic plants had normal growth and sprouted up to 97.8%. Phytoplasma transmission by dodder bridges to periwinkle did not succeed, while nested polymerase chain reaction on the phytoplasma ribosomal gene followed by RFLP and phylogenetic analyses revealed the presence of ‘Candidatus Phytoplasma asteris’, ‘Ca. P. australasiae=australasiaticum’, and ‘Ca. P. trifolii’ (ribosomal subgroups 16SrI-B, 16SrII-D, and 16SrVI-A, respectively) in the samples from symptomatic plants only. Further amplifications were performed on selected phytoplasma-positive samples on tuf and secA genes, and the produced sequences indicated the presence of mixed phytoplasma infection in some of the samples. In particular, in the tuf gene, a mixed infection of ‘Ca. P. australasiae=australasiaticum’ and ‘Ca. P. trifolii’ was detected, while in the secA gene, the presence of ‘Ca. P. asteris’ or ‘Ca. P. tritici’ strains was identified. The first-time detection of diverse phytoplasma strains in symptomatic T. aphylla suggests that this species represent a relevant source of infection for the agricultural crops and for landscape plants especially when temperature allows insect vector transmission, and therefore, it represents a risk in every environment especially in the frame of climatic changes. Full article

Phytoplasmas are insect-transmitted bacterial pathogens associated with diseases in a wide range of host plants, resulting in significant economic and ecological losses. Perennial deciduous trees in the genus Paulownia are widely planted for wood harvesting and ornamental purposes. Paulownia witches’ broom (PaWB) disease, associated with a 16SrI-D subgroup phytoplasma, is a destructive disease of paulownia in East Asia. The PaWB phytoplasmas are mainly transmitted by insect vectors in the Pentatomidae (stink bugs), Miridae (mirid bugs) and Cicadellidae (leafhoppers) families. Diseased trees show typical symptoms, such as branch and shoot proliferation, which together are referred to as witches’ broom. The phytoplasma presence affects the physiological and anatomical structures of paulownia. Gene expression in paulownia responding to phytoplasma presence have been studied at the transcriptional, post-transcriptional, translational and post-translational levels by high throughput sequencing techniques. A PaWB pathogenic mechanism frame diagram on molecular level is summarized. Studies on the interactions among the phytoplasma, the insect vectors and the plant host, including the mechanisms underlying how paulownia effectors modify processes of gene expression, will lead to a deeper understanding of the pathogenic mechanisms and to the development of efficient control measures. Full article

Phytoplasmas are intracellular pathogenic bacteria that infect a wide range of plant species, including agriculturally important crops and ornamental trees. However, our understanding of the relationship between symptom severity, disease progression, and phytoplasma concentration remains limited due to the inability to inoculate phytoplasmas mechanically into new plant hosts. The present study investigated phytoplasma titer dynamics and symptom development in periwinkle and tomato, both infected with the same potato purple top (PPT) phytoplasma strain using a small seedling grafting approach. Virescence, phyllody, and witches’-broom (WB) symptoms sequentially developed in periwinkle, while in tomato plants, big bud (BB, a form of phyllody), cauliflower-like inflorescence (CLI), and WB appeared in order. Results from quantitative polymerase chain reaction (qPCR) targeting the PPT phytoplasma’s 16S rRNA gene revealed that in both host species, phytoplasma titers differed significantly at different infection stages. Notably, the highest phytoplasma concentration in periwinkles was observed in samples displaying phyllody symptoms, whereas in tomatoes, the titer peaked at the BB stage. Western blot analysis, utilizing an antibody specific to PPT phytoplasma, confirmed substantial phytoplasma presence in samples displaying phyllody and BB symptoms, consistent with the qPCR results. These findings challenge the conventional understanding that phytoplasma infection dynamics result in a higher titer at later stages, such as WB (excessive vegetative growth), rather than in the early stage, such as phyllody (abnormal reproductive growth). Furthermore, the PPT phytoplasma titer was markedly higher in periwinkles than in tomato plants, indicating differing susceptibilities between the hosts. This study reveals distinct host responses to PPT phytoplasma infection, providing valuable insights into phytoplasma titer dynamics and symptom development, with implications for the future management of agricultural disease. Full article

Camptotheca acuminata Witches’-broom disease (CaWB) is the most destructive disease affecting C. acuminata in China. Previous studies on CaWB have failed to clarify the incidence pattern in C. acuminata after infection with phytoplasma. The time interval between phytoplasma infection of C. acuminata and the onset of Witches’-broom symptoms in C. acuminata was very long. C. acuminata inoculated with CaWB showed leaf margin scorching symptoms at 4 weeks in inoculated leaves. At 16 weeks after infection (WAI), old leaves were shed, while new leaves showed a mild leaf margin scorch; at 28 WAI, typical symptoms appeared. Transcriptomic and metabolomic analyses of the three sampling periods revealed 194 differentially expressed genes, mainly enriched in MAPK signaling, plant–pathogen interaction, phenylpropanoid biosynthesis, starch and phenylpropanoid biosynthesis, and phenylpropanoid biosynthesis pathways. The expression of calcium-dependent protein kinase (CDPK), β Ketoacyl-CoA Synthase1/10 (KCS1/10), and WRKY22/29 genes in the plant–pathogen interaction pathway significantly increased, indicating that they may be key genes in the CaWB phytoplasma-mediated maintenance of ROS homeostasis. Moreover, isochlorogenic acid B, atractylenolide II, and 3-methoxybenzoic acid were found, which might serve as signaling or functional substances in the defense response. Our results provide novel insights into the pathogenesis of CaWB and the defense response of C. acuminata under the influence of phytoplasma. Additionally, we identified potential candidate genes related to the defense response of C. acuminata, laying the foundation for further research. Full article