Broom Disease Research Articles

Selection of Theobroma grandiflorum clones adapted to agroforestry systems using an additive index

In fruit tree breeding, selection indices are used to identify the genotypes that combine desirable commercial and non-commercial characteristics. As Theobroma grandiflorum is generally cultivated in agroforestry systems (AFS), there is a need to develop cultivars that are adapted to such environments. In this study, the objective was to select the most promising genotypes for their future use in AFS based on the additive index, a pioneering method for this crop. The trial was carried out for 12 years in an agroforestry system in the municipality of Tomé-Açu, Pará State, Brazil. The 16 evaluated clones were completely randomised with a variable number of repetitions. The average number of fruits produced as well as the morpho-agronomic characteristics of the fruits were analysed. Mixed linear models were used to estimate the components of variance and predict the genotypic values. The genetic correlation between the variables was estimated, and the selection of genotypes was based on the additive index, with a positive orientation of all variables except the thickness of the fruit shells and the weight of the fruits. Clones 42, 44, 46, 47, 57, 61, and 64 performed well for all the analysed variables, resulting in a selection gain of 7.3% and low incidence rates of witches’ broom disease. These genotypes can be made available to producers in the form of clones for use in AFS and can further be included in future hybridisations in T. grandiflorum breeding.

Comparative transcriptomics of cupuassu (Theobroma grandiflorum) offers insights into the early defense mechanism to Moniliophthora perniciosa, the causal agent of witches’ broom disease

ABSTRACT Cupuassu (Theobroma grandiflorum) is a fruit tree native to the Amazon region, presenting high social and economic value. Besides, owing to its suitability for agroforestry cultivation, cupuassu is useful for the conservation of the Amazon Forest. Cupuassu plantations are severely affected by Moniliophthora perniciosa. Thus, to gain insights into resistance against M. perniciosa, transcriptomes of susceptible (SG) and resistant (RG) genotypes of cupuassu were analyzed at the early stage of infection using RNA sequencing. A total of 21,441 unigenes were identified, and differentially expressed genes were detected in intra- (440) and inter-genotype (301) analyses. Gene expression was altered at 24 h after inoculation (HAI) in SG. This alteration was prominent at 48 HAI in RG. These datasets allowed the identification of genes potentially involved in defense mechanisms. Phytohormone signature analysis revealed a significant effect of hormones on genotype responses. The present study is the first large-scale transcriptomic analysis of cupuassu.

First Report of Phytoplasma Belongs to 16SrV Group Associated with Witches'-broom Disease of Taxillus chinensis in China.

Taxillus chinensis (DC.) Danser is a hemiparasitic shrub, widespread in Southern China (Fu et al., 2001). T. chinensis can parasitize a wide range of species (e.g., Camellia spp., Ficus virens and Osmanthus fragrans), which obviously suppressed host growth by robbing nutrient and water through haustorium, causing considerable tree damage. During field visits to Dongguan (22°86'N, 13°97'E) and Guangzhou (23°19'N, 113°31'E), Guangdong Province, in April-July 2021, the typical phytoplasma-suspected symptom manifested as stunting, leaflet, leaf chlorosis and witches'-broom were observed in almost 36% of T. chinensis plants. Leaf samples were collected from six randomly collected plants with symptoms and six symptomless plants (Fig 1). Among them, half of T. chinensis plants parasitized on the host Elaeocarpus sylvestris, the other half on the O. fragrans. No apparent symptoms were observed on both two host plants. Total DNA was extracted from 0.5 g fresh leaf of T. chinensis plants with and without symptoms, as well as two host plants E. sylvestris and O. fragrans, using the CTAB method (Doyle et al., 1990). Nested polymerase chain reactions (PCRs) were performed on DNA extracts of all tested plants with primer pairs of P1/P7 and R16mF2/R16mR1 for 16S rRNA gene (Lee et al., 1993) and rp(v)F1/rpR1 for rp gene (Lee et al., 1998). All amplicons were obtained from symptomatic samples of T. chinensis and host plant E. sylvestris, whereas no such products resulted from DNAs of symptomless plants and O. fragrans. The amplicons were purified and sequenced by Sanger method (Rui Biotech, Guangzhou, China). The amplicon of 16S rRNA and rp genes is 1346 bp and 938 bp, respectively. BLAST comparison of the 16S rRNA (accession no. OL412744) and rp (accession no. OL473789) sequences of the T. chinensis witches'-broom phytoplasma yielded 99.6% sequence identity with those of phytoplasmas of group 16SrV jujube witches'-broom (JWB) phytoplasma (accession no. CP025121 for 16S rRNA gene and AF396941 for rp gene). The 16S rRNA gene sequence of phytoplasma in host plant E. sylvestris (accession no. OM885990) is 99.7% similarity to the 'Elaeocarpus zollingeri' yellows phytoplasma (accession no. LC257960) and 99.4% similarity to the 'Elaeocarpus sylvestris' decline phytoplasma (accession no. MW553140), but 95.8% similarity to the 16S rRNA gene of phytoplasma in T. chinensis. The virtual RFLP tool, iPhyClassifier delineated the T. chinensis phytoplasma (accession no. OL412744) to group 16SrV-B (accession no. AB052876) with the similarity coefficient 1.0 (Fig 2), and phytoplasma in E. sylvestris to group 16Sr group XXXII with the similarity coefficient 0.97. Phylogeny analyses of 16S rRNA and rp genes (MEGA version 7.0.14, USA) using reference phytoplasmas from GenBank confirmed sequencing results and placed the T. chinensis phytoplasma in group 16SrV-B (Fig. 3 and 4). In China, the 16SrV-B phytoplasma group has been reported in Amaranthus retroflexus (Yang et al., 2011), Liriodendron chinense (Li et al., 2012), Prunus salicina (Gao et al., 2020) and sweet potato (Li et al., 2021). This is the first report of a 'Ca. Phytoplasma ziziphi', 16SrV-B related phytoplasma associated with parasitic T. chinensis in China. The results of this study indicate that T. chinensis could be a vector to spread phytoplasmas 16SrV group through parasitism and this can be helpful for related research.

Molecular Diversity and Evolutionary Relatedness of Paulownia Witches’-Broom Phytoplasma in Different Geographical Distributions in China

To reveal the distribution and transmission pathway of Paulownia witches'-broom (PaWB) disease, which is caused by phytoplasmas related to genetic variation, and the adaptability to the hosts and environments of the pathogenic population in different geographical regions in China, in this study, we used ten housekeeping gene fragments, including rp, fusA, secY, tuf, secA, dnaK, rpoB, pyrG, gyrB, and ipt, for multilocus sequence typing (MLST). A total of 142 PaWB phytoplasma strains were collected from 18 provinces or municipalities. The results showed that the genetic diversity was comparatively higher among the PaWB phytoplasma strains, and substantially different from that of the other 16SrI subgroup strains. The number of gene variation sites for different housekeeping genes in the PaWB phytoplasma strains ranged from 1 to 14 SNPs. Among them, rpoB (1.47%) and dnaK (1.12%) had higher genetic variation, and rp (0.20%) had the least genetic variation. The tuf and rpoB genes showed the fixation of positively selected beneficial mutations in the PaWB phytoplasma populations, and all housekeeping genes except tuf followed the neutral evolutionary model. We found an absence of recombination among PaWB phytoplasma sequence types (STs) for each housekeeping gene except dnaK, and no evidence for such recombination events for concatenated sequences of PaWB phytoplasma strains. The 22 sequence types were identified among the concatenated sequences of seven housekeeping genes (rp, fusA, secY, secA, tuf, dnaK, and rpoB) from 105 representative strains. We analyzed all 22 STs by goeBURST algorithm, forming two clonal complexes (CCs) and three singletons. Among them, ST1, as the primary founder of CC1, had the widest geographical distribution, accounting for 72.38% of all strains, with a high frequency of shared sequence type. The results of phylogenetic analysis of the concatenated sequences further revealed that the 105 strains were clustered into two representative lineages of PaWB phytoplasma, with obvious geographical differentiation. The ST1 strains of highly homogeneous lineage-1 were a widespread and predominant population in diseased areas. Lineage-2 contained strains from Jiangxi, Fujian, and Shaanxi provinces, highlighting the close genetic relatedness of the strains in these regions, which was also consistent with the results of most single-gene phylogenetic analysis of each gene. We also found that the variability in the northwest China population was higher than in other geographical populations; the range of genetic differentiation between the south of the Yangtze River population and the Huang-huai-hai Plain (or southwest China) population was relatively large. The achieved diversity and evolution data, as well as the MLST technique, are helpful for epidemiological studies and guiding PaWB disease control decisions.

Pathogenic study on jujube witches’ broom disease through multi-omics analysis

Pathogenic study on jujube witches’ broom disease through multi-omics analysis

Integrated full-length transcriptome and metabolome analysis of the early defense mechanisms in Paulownia witches’ broom disease

ABSTRACT Paulownia witches’ broom (PaWB) is a devastating disease of Paulownia spp. caused by phytoplasma infection. To reveal the reason for the absence of morphological changes at the early stage of phytoplasma infection, in this study, a combination of second-and third-generation sequencing (single-molecule real-time long-read isoform) and liquid chromatography tandem mass spectrometry were performed to analyse the changes of full-length transcripts and metabolites at the early stage of phytoplasma infection. A total of 140,528 non-redundant full-length transcripts, 597 transcription factors, 1,658 long non-coding RNAs, and 645 metabolites were identified. The third-generation sequencing improved the annotation of the reference Paulownia fortunei (Seem.) Hemsl. genome by 8.86%. Combination analysis of the full-length transcriptome and metabolome revealed that phenolics and phenylalanine ammonia-lyase synthesis related genes were significantly up-regulated in the early stage of phytoplasma-infected P. fortunei. Based on the results of full-length transcriptome and metabolome integrative analysis, we constructed an early defence model diagram of PaWB disease. Our results provide powerful insights into the reason for absence of morphological at the early stage of phytoplasma infection.

Candidatus Phytoplasma Australasia Associated with Alfalfa Witches’ Broom: Symptomatology, Quantitative Loss, Qualitative Loss and Molecular Characterization

Background: Alfalfa, Medicago sativa L. is the most important and widely grown leguminous fodder crop in temperate and tropical regions of the world. The production of alfalfa crop is limited by several biotic stresses, among which witches’ broom disease (AWB) was reported to cause significant economic losses. Methods: The phytoplasma infected alfalfa plants were collected from a central research farm, ICAR-IGFRI, Jhansi, U.P. Qualitative parameters such as crude protein content, acid detergent fibre and neutral detergent fibre were estimated in diseased and healthy plants. Phytoplasma universal primer (P1/P7) and nested primer (R16mF2/R16mR1) were used for the molecular characterization of AWB infected plants and phytoplasma infected, Parthenium hysterophorus. Result: The incidence of AWB disease ranged from 8-10%. The quantitative analysis of disease plants showed reduced plant height (-35%), fresh weight (-46.89%) and dry weight (-50.08%) compared to healthy plants. The diseased plant recorded low crude protein content (-21.38%) and higher dry matter content (+0.68%), acid detergent fibre (+33.72%) and neutral detergent fibre (+13.06%). The association of phytoplasma in diseased alfalfa and parthenium samples was confirmed by using P1/P7 and R16mF2/R16mR1 primer pair and Blastn analysis shared 99.6-100% similarity with ‘Candidatus Phytoplasma australasia’ belongs to the 16Sr group II-D.

Taxonomy and phylogeny of Exobasidium pentasporium causing witches' broom of Rhododendron species.

Exobasidium pentasporium was first found on Rhododendron kaempferi in Nikko, Tochigi Prefecture, Japan and described only with a brief mentions and illustration of a specimen in 1896. This fungus causes a witches' broom disease of Rhododendron species. To stabilize the concept of this species, the specimen in the protologue was located, carefully examined, and illustrated. In addition, the name was epitypified based on a newly collected topotype specimen. A phylogenetic tree using ITS and LSU sequences showed that our isolates of E. pentasporium grouped with other Exobasidium species on Rhododendron forming a monophyletic clade with strong statistical support and were unrelated to E. nobeyamense, another causal agent of witches' broom disease on Rhododendron species.

Molecular and biological characterization of ‘Candidatus Phytoplasma aurantifolia’ strains infecting commercial citrus species in Iran

In a 2017 survey, witches’ broom disease (WBD) of Mexican lime (WBDL), Bakraee (WBDB), grapefruit (WBDGF), Kinnow (WBDK), Orlando tangelo (WBDOT), Minneola tangelo (WBDMT), sweet oranges varieties Valencia (WBDVSO) and a local (WBDLoSO) were observed in the Hormozgan province of Iran. The agents of citrus WBD were graft transmitted to lime seedlings and from lime seedlings to periwinkle plants via dodder. The work revealed that disease symptoms in lime seedlings and periwinkle plants are biological features for differentiating 16SrII-B and 16SrII-C strains. Phylogenetic and Tsp509I enzyme virtual RFLP analyses and presence of the ‘Candidatus Phytoplasma aurantifolia’ (16SrII-B) signature revealed that phytoplasmas detected in the present study and those from WBDVSO, WBDOT and WBD of citron (Kerman province, Iran) previously reported as 16SrII-C phytoplasma strains, are members of 16SrII-B subgroup. WBDK, WBDOT, WBDMT, WBDVSO and WBDLo association with 16SrII-B phytoplasmas is reported for the first time in the world.

First report of ‘Candidatus Phytoplasma phoenicium’ (16SrIX-B) and ‘Candidatus Phytoplasma aurantifolia’ (16SrII-C) related strains on greengage trees

During 2021 surveys, greengage witches’-broom (GWB) and decline (GD) diseases were respectively observed in Fars and Yazd provinces of Iran. Presence of phytoplasma in the symptomatic plants was confirmed by PCR amplifications of 16S rRNA gene. Sequence analyses showed affiliation of the GWB and GD phytoplasmas to‘Candidatus Phytoplasma phoenicium’ (16SrIX-B) and‘Ca. P. aurantifolia’ (16SrII-C) related strains, respectively. This is the first report of phytoplasma diseases of greengage in Iran and probably in the world.

Cacao agroforestry systems beyond the stigmas: Biotic and abiotic stress incidence impact.

Low technological knowledge in production chains, global climate change, and misinformation are concrete threats to food security. In addition, these combined threats also trigger ecological instability in megadiverse areas of the world, especially in some cacao-producing countries in South America, where this crop plays an important socio-economic role, even being used to replace illicit crops. Accordingly, the use of agroforestry systems approaches has emerged as a good alternative to maintain productivity, add high-value commodities to producers, and provide important ecosystem services for sustainable agriculture. However, limitations associated with the competition for resources between the species composing the system, and the higher incidence of some diseases, have led many producers to abandon this strategy, opting for monoculture. In this review, we seek to gather the main information available in the literature, aiming to answer the question: what is the real scientific evidence that supports the benefits and harms of adopting agroforestry systems in cacao production? We seek to make critical scrutiny of the possible negative effects of certain associations of the agroforestry system with biotic and abiotic stress in cacao. Here, we review the possible competition for light and nutrients and discuss the main characteristics to be sought in cacao genotypes to optimize these inter-specific relationships. In addition, we review the research advances that show the behavior of the main cacao diseases (Witch’s broom disease, frosty pod rot, black pod rot) in models of agroforestry systems contrasted with monoculture, as well as the optimization of agronomic practices to reduce some of these stresses. This compendium, therefore, sheds light on a major gap in establishing truly sustainable agriculture, which has been treated much more from the perspective of negative stigma than from the real technological advantages that can be combined to the benefit of a balanced ecosystem with generating income for farmers.

Study of the Pathogenicity of Moniliophthora spp. Isolates from Branches of Kola Trees (Cola nitida (Vent) Scott and Endl.) Infected with witches Broom Disease

Study of the Pathogenicity of Moniliophthora spp. Isolates from Branches of Kola Trees (Cola nitida (Vent) Scott and Endl.) Infected with witches Broom Disease

Combined transcriptome and metabolome analysis of Nerium indicum L. elaborates the key pathways that are activated in response to witches’ broom disease

BackgroundNerium indicum Mill. is an ornamental plant that is found in parks, riversides, lakesides, and scenic areas in China and other parts of the world. Our recent survey indicated the prevalence of witches’ broom disease (WBD) in Guangdong, China. To find out the possible defense strategies against WBD, we performed a MiSeq based ITS sequencing to identify the possible casual organism, then did a de novo transcriptome sequencing and metabolome profiling in the phloem and stem tip of N. indicum plants suffering from WBD compared to healthy ones.ResultsThe survey showed that Wengyuen county and Zengcheng district had the highest disease incidence rates. The most prevalent microbial species in the diseased tissues was Cophinforma mamane. The transcriptome sequencing resulted in the identification of 191,224 unigenes of which 142,396 could be annotated. There were 19,031 and 13,284 differentially expressed genes (DEGs) between diseased phloem (NOWP) and healthy phloem (NOHP), and diseased stem (NOWS) and healthy stem (NOHS), respectively. The DEGs were enriched in MAPK-signaling (plant), plant-pathogen interaction, plant-hormone signal transduction, phenylpropanoid and flavonoid biosynthesis, linoleic acid and α-linoleic acid metabolism pathways. Particularly, we found that N. indicum plants activated the phytohormone signaling, MAPK-signaling cascade, defense related proteins, and the biosynthesis of phenylpropanoids and flavonoids as defense responses to the pathogenic infection. The metabolome profiling identified 586 metabolites of which 386 and 324 metabolites were differentially accumulated in NOHP vs NOWP and NOHS and NOWS, respectively. The differential accumulation of metabolites related to phytohormone signaling, linoleic acid metabolism, phenylpropanoid and flavonoid biosynthesis, nicotinate and nicotinamide metabolism, and citrate cycle was observed, indicating the role of these pathways in defense responses against the pathogenic infection.ConclusionOur results showed that Guangdong province has a high incidence of WBD in most of the surveyed areas. C. mamane is suspected to be the causing pathogen of WBD in N. indicum. N. indicum initiated the MAPK-signaling cascade and phytohormone signaling, leading to the activation of pathogen-associated molecular patterns and hypersensitive response. Furthermore, N. indicum accumulated high concentrations of phenolic acids, coumarins and lignans, and flavonoids under WBD. These results provide scientific tools for the formulation of control strategies of WBD in N. indicum.

A high-density genetic map from a cacao F2 progeny and QTL detection for resistance to witches’ broom disease

A high-density genetic map from a cacao F2 progeny and QTL detection for resistance to witches’ broom disease

Development of loop-mediated isothermal amplification (LAMP) assay for the detection of clover proliferation phytoplasma-associated with sweet cherry witches’ broom disease

Development of loop-mediated isothermal amplification (LAMP) assay for the detection of clover proliferation phytoplasma-associated with sweet cherry witches’ broom disease

Distinct Taphrina strains from the phyllosphere of birch exhibiting a range of witches' broom disease symptoms.

SummaryThe phyllosphere is an important microbial habitat and reservoir of organisms that modify plant health. Taphrina betulina is the causal agent of birch witches' broom disease. Taphrina species are dimorphic, infecting hosts in the filamentous form and residing in the host phyllosphere as non‐infectious yeast. As such, they are expected to be found as resident yeasts on their hosts, even on healthy tissues; however, there is little experimental data supporting this supposition. With the aim of exploring the local infection ecology of T. betulina, we isolated yeasts from the phyllosphere of birch leaves, using three sample classes; infected leaves inside symptom‐bearing branches, healthy leaves from symptom‐free branches on symptom‐bearing trees and leaves from symptom‐free branches on symptom‐free trees. Isolations yielded 224 yeast strains, representing 11 taxa, including T. betulina, which was the most common isolate and was found in all sample classes, including symptom‐free samples. Genotyping revealed genetic diversity among these T. betulina isolates, with seven distinct genotypes differentiated by the markers used. Twenty‐two representative T. betulina strains were selected for further study, revealing further phenotypic differences. These findings support that T. betulina is ubiquitous on birch and that individual trees host a diversity of T. betulina strains.

The Jujube TCP Transcription Factor ZjTCP16 Regulates Plant Growth and Cell Size by Affecting the Expression of Genes Involved in Plant Morphogenesis

Jujube production is threatened by jujube witches’ broom (JWB) disease, which is caused by JWB phytoplasma. The jujube TCP transcription factor (TF) ZjTCP16 may be involved in the interaction of jujube plants with JWB phytoplasma. In this study, qRT-PCR proved that the expression pattern of ZjTCP16 was altered by JWB phytoplasma. The gene functions of ZjTCP16 were analyzed by its overexpression in Arabidopsis and jujube, as well as knock-down in. The overexpression of ZjTCP16 in Arabidopsis and jujube resulted in dwarfism and small leaves, while the zjtcp16 CRISPR mutants were higher than the WT. Microscopic observation of paraffin sections of jujube stems showed that ZjTCP16 affected the size of cells. The interactions of ZjTCP16 with ZjAS2 and ZjLOB in both the cytoplasm and nucleus were demonstrated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Yeast one-hybrid (Y1H) assays and qRT-PCR further confirmed that ZjTCP16 affected the expression of genes involved in leaf morphogenesis and cell proliferation (ZjAS1, ZjKNAT1, ZjKNAT2 and ZjKNAT6) at the mRNA level through the ZjAS2 and ZjLOB pathways. In conclusion, ZjTCP16 regulates plant growth and cell size by altering the expression pattern of morphogenesis-related genes in jujube.

A molecular diagnostic for Moniliophthora perniciosa, the causal agent of witches' broom disease of cacao, that differentiates it from its sister taxon Moniliophthora roreri

Moniliophthora perniciosa is a hemibiotrophic plant pathogen that causes witches' broom disease (WBD) in Theobroma, Herrania, and other plant species. This disease is one of the primary threats that reduce the yield of cacao and cupuaçu plantations in Tropical America. Thereby, there is a growing concern that the pathogen may spread to other areas. The fungus can infect flowers, pods, and stems, causing various symptoms, including stem swellings and dark brown necrotic pods. In some cases, these symptomatologies are very similar to other cacao diseases, such as the black pod (Phytophthora spp.) and frosty pod rot (M. roreri) of cacao. Pathogens isolation and identification from diseased samples need expertise. Thus, the objective of this work was to develop a diagnostic guide with standard procedures with the aid of a molecular marker for M. perniciosa identification that is specific, sensitive, and cost-effective. A genomics-based approach was used to identify unique primer pairs to M. perniciosa. The specificity of 24 primer pairs in identifying M. perniciosa from pure culture gDNA was evaluated by conventional polymerase chain reaction (PCR) with approximately 400 isolates from ten fungal species of common occurrence in cacao plantations, including M. roreri. No amplicon was detected from other fungal species, confirming the high specificity and sensibility of the M. perniciosa specific markers Mp44 and Mp47 for molecular identification of M. perniciosa from pure culture. Finally, the present study provides a set of standardized WBD diagnosis procedures that associate a classical with a molecular approach by PCR-based identification of M. perniciosa.

The Crosstalk of the Salicylic Acid and Jasmonic Acid Signaling Pathways Contributed to Different Resistance to Phytoplasma Infection Between the Two Genotypes in Chinese Jujube

Jujube witches’ broom disease (JWB), one of the most serious phytoplasma diseases, usually results in the destruction of Chinese jujube (Ziziphus jujuba Mill.). Although most jujube cultivars are sensitive to JWB, we found a few genotypes that are highly resistant to JWB. However, the molecular mechanism of phytoplasma resistance has seldom been studied. Here, we used Chinese jujube “T13,” which has strong resistance to JWB, and a typical susceptible cultivar, “Pozao” (“PZ”), as materials to perform comparative transcriptome, hormone, and regulation analyses. After phytoplasma infection, the differential expression genes (DEGs) were detected at all three growth phases (S1, S2, and S3) in “PZ,” but DEGs were detected only at the first growth phase in “T13.” Meanwhile, no phytoplasma was detected, and the symptoms especially witches’ broom caused by JWB were not observed at the last two growth phases (S2 and S3) in “T13.” Protein–protein interaction analysis also showed that the key genes were mainly involved in hormone and reactive oxygen species (ROS) signaling. In addition, during the recovered growth phase in “T13” from S1 to S2, the level of hydrogen peroxide (H2O2) was significantly increased and then decreased from S2 to S3. Moreover, jasmonic acid (JA) was significantly accumulated in “PZ” diseased plants, especially at the S2 phase and at the S2 phase in “T13,” while the content of salicylic acid (SA) decreased significantly at the S2 phase of “T13” compared to that in “PZ.” The changes in H2O2 and JA or SA were consistent with the changes in their key synthesis genes in the transcriptome data. Finally, exogenous application of an SA inhibitor [1-aminobenzotriazole (ABT)] rescued witches’ broom symptoms, while the contents of both JA and MeJA increased after ABT treatment compared to the control, demonstrating that exogenous application of an SA inhibitor rescued the symptoms of jujube after phytoplasma infection by decreasing the contents of SA and increasing the contents of JA and MeJA. Collectively, our study provides a new perspective on the transcriptional changes of Chinese jujube in response to JWB and novel insights that the crosstalk of JA and SA signaling communicated together to contribute to “T13” JWB resistance.

Transgenic tomato expressing an oxalate decarboxylase gene from Flammulina sp. shows increased survival to Moniliophthora perniciosa

Witches’ broom disease which affects cacao tree (Theobroma cacao L.) is caused by the hemibiotrophic fungus Moniliophthora perniciosa. Studies of the cacao-M. perniciosa interaction showed that the pathogenicity of M. perniciosa is associated to the presence of oxalic acid (OA). In some organisms, OA can be degraded into formate and CO2 by the oxalate decarboxylase (OXDC) enzyme. Here, we used the oxdc gene from Flammulina velutipes to generate transgenic tomato plants as a potential strategy to control M. perniciosa infection. Three transgenic T1 lines expressing the oxdc gene were obtained and two of them (P4 and P16) presented a significant delay in symptom development and higher survival percentage when inoculated with M. perniciosa in comparison to the non-transformed wild-type (WT) plants. Moreover, the P16 line test showed a decreased production of H2O2 in the presence of OA in comparison to the WT, as evidenced by the 3,3′-diaminobenzidine test. These results indicate that the P16 transgenic line is able to break down OA leading to normal plant development with few symptoms even when infected by M. perniciosa. Phenotypic and histological analysis showed differences between WT and transgenic plants. The amount of fungus hyphae was lower with thinner thickness in the transgenic plants. This study evidences of the reduction of witches’ broom disease progression by the presence of the oxdc gene leading to the plant survival.