Agronomy

Research

21 pages, 2299 KiB

Open AccessArticle

Metabolomic, Ionomic and Microbial Characterization of Olive Xylem Sap Reveals Differences According to Plant Age and Genotype

by Manuel Anguita-Maeso, Carmen Haro, Miguel Montes-Borrego, Leonardo De La Fuente, Juan A. Navas-Cortés and Blanca B. Landa

Agronomy 2021, 11(6), 1179; https://doi.org/10.3390/agronomy11061179 - 10 Jun 2021

Cited by 22 | Viewed by 4485

Abstract

Vascular pathogens are the causal agents of main diseases threatening the health and growth of olive crops worldwide. The use of endophytic microorganisms represents a challenging and promising strategy for management of vascular diseases in olive. Although current research has been focused on [...] Read more.

Vascular pathogens are the causal agents of main diseases threatening the health and growth of olive crops worldwide. The use of endophytic microorganisms represents a challenging and promising strategy for management of vascular diseases in olive. Although current research has been focused on analyzing the structure and diversity of the endophytic microbial communities inhabiting the olive xylem, the characterization of this ecological niche has been overlooked and to date remain unexplored, despite that the characterization of the xylem sap composition is essential to unravel the nutritional requirements of xylem-limited microorganisms. In this study, branches from plantlets and adult olive trees of cultivars Picual and Arbequina were selected to characterize the chemical and microbial composition of olive xylem sap extracted using a Scholander pressure chamber. Metabolome and ionome analyses of xylem sap were performed by proton nuclear magnetic resonance (NMR) spectroscopy-based and by inductively coupled plasma with optical emission spectroscopy (ICP-OES), respectively. Olive xylem sap metabolites included a higher relative percentage of sugars (54.35%), followed by alcohols (28.85%), amino acids (8.01%), organic acids (7.68%), and osmolytes (1.12%). Within each of these groups, the main metabolites in the olive xylem sap were mannitol, ethanol, glutamine, acetic acid, and trigonelline, whereas K and Cl⁻ were the main element and inorganic anion, respectively. Metabolomic profile varied when comparing olive plant age and genotype. The levels of glucose, fructose, sucrose and mannitol, choline, B and PO₄³⁻ were significantly higher in adult trees than in plantlets for both olive genotypes, whereas NO³⁻ and Rb content showed the opposite behavior. On the other hand, levels of aspartic acid, phenylalanine, and Na were significantly higher in ‘Picual’ than in ‘Arbequina’, whereas Fe showed the opposite behavior, but only for adult trees. Microbiome composition identified Firmicutes (67%), Proteobacteria (22%) and Actinobacteriota (11%) as the main phyla, while at the genus level Anoxybacillus (52%), Cutibacterium (7%), Massilia (6%), and Pseudomonas (3%) were the most representative. Both non-supervised hierarchical clustering analysis and supervised PLS-DA analysis differentiated xylem sap chemical and microbial composition first, according to the age of the plant and then by the olive genotype. PLS-DA analysis revealed that B, ethanol, Fe, fructose, glucose, mannitol, sucrose, and Sr, and Anoxybacillus, Cutibacterium, and Bradyrhizobium were the most significant chemical compounds and bacterial genera, respectively, in the discrimination of adult olive trees and plantlets. Knowledge of the chemical composition of xylem sap will lead to a better understanding of the complex nutritional requirements of olive xylem-inhabiting microorganisms, including vascular pathogens and their potential antagonists, and may allow the better design of artificial growing media to improve the culturing of the olive microbiome. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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14 pages, 487 KiB

Open AccessArticle

Detection and Diagnosis of Xylella fastidiosa by Specific Monoclonal Antibodies

by María Teresa Gorris, Antonio Sanz, Javier Peñalver, María M. López, Mario Colomer and Ester Marco-Noales

Agronomy 2021, 11(1), 48; https://doi.org/10.3390/agronomy11010048 - 28 Dec 2020

Cited by 7 | Viewed by 3838 | Correction

Abstract

Monoclonal antibodies (MAb) specific to Xylella fastidiosa were obtained through hybridoma technology using heat-treated somatic O antigens from LMG 17159strain. Ten stable hybrydoma clones secreting MAb were selected and their isotype was determined. The MAbs 2G1/PPD, IgG₁ showed specificity for X. fastidiosa [...] Read more.

Monoclonal antibodies (MAb) specific to Xylella fastidiosa were obtained through hybridoma technology using heat-treated somatic O antigens from LMG 17159strain. Ten stable hybrydoma clones secreting MAb were selected and their isotype was determined. The MAbs 2G1/PPD, IgG₁ showed specificity for X. fastidiosa, detecting all the analyzed strains representing different subspecies, STs and hosts. Polyclonal antibodies (PAb) against X. fastidiosa were also produced and antiserum 17159-O/IVIA was selected for the highest titre and its excellent detection capability. MAb 2G1/PPD was tested against strain IVIA 5235 in PBS and in spiked raw extract samples from almond, olive, citrus, and other hosts and its sensitivity by DAS-ELISA was 10⁴ CFU mL⁻¹. The MAb also reacted with high affinity and avidity against X. fastidiosa by DASI-ELISA and Tissue print-ELISA. The diagnostic parameters of DAS-ELISA based on MAb were calculated and compared with the gold standard real-time PCR. The diagnostic specificity of MAb2G1/PPD was 100%, the diagnostic sensitivity was 88.5% compared to Harper’s real-time PCR and 89.9% compared to Francis’ real-time PCR. The agreement between the techniques was almost perfect according to the estimated Cohen’s kappa-index, even in symptomless almond trees. The developed immunological techniques represent sustainable and low-cost analysis tools, based on specific, homogeneous, and well-characterized MAbs, which can be obtained in unlimited quantities in a reproducible way and constitute a guarantee for the standardization of commercial kits. They are a valuable option within a polyphasic strategy for the detection of X. fastidiosa. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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13 pages, 1322 KiB

Open AccessArticle

The Challenge of Environmental Samples for PCR Detection of Phytopathogenic Bacteria: A Case Study of Citrus Huanglongbing Disease

by Félix Morán, Silvia Barbé, Saskia Bastin, Inmaculada Navarro, Edson Bertolini, María M. López, Estrella Hernández-Suárez, Alberto Urbaneja, Alejandro Tena, Felipe Siverio and Ester Marco-Noales

Agronomy 2021, 11(1), 10; https://doi.org/10.3390/agronomy11010010 - 23 Dec 2020

Cited by 6 | Viewed by 4225

Abstract

Huanglongbing (HLB) is the most devastating citrus disease and is associated with three bacterial species of the genus ‘Candidatus Liberibacter’ transmitted by insect vectors. The early detection of HLB is based on PCR methods, and it is one of the cornerstones for [...] Read more.

Huanglongbing (HLB) is the most devastating citrus disease and is associated with three bacterial species of the genus ‘Candidatus Liberibacter’ transmitted by insect vectors. The early detection of HLB is based on PCR methods, and it is one of the cornerstones for preventing incursion into disease-free countries. However, the detection of phytopathogenic bacteria with PCR-based methods is problematic in surveys that include a variety of samples of different origins. Here, we first report the proportion of amplifications obtained by two standardized real-time PCR methods for the diagnosis of HLB in various environmental samples that include plants, psyllid vectors, and parasitic wasps of the psyllids. The results of 4915 samples showed that 9.3% of them were amplified by the first rapid screening test and only 0.3% by the more specific tests. Most of the amplifications were associated with parasitic wasps. We designed the primers external to the target regions of both real-time PCR protocols to determine if amplifications belonged to one of three ‘Ca. Liberibacter’ species associated with HLB. The bioinformatic analysis of the sequences obtained with these primers revealed that all these amplifications came from the presence of other prokaryotic organisms in the samples. The primers developed in this study overcome the problem of undesired amplification in environmental samples. Thus, they could be used in future survey protocols to prevent the eradication of negative trees and the generation of unjustified alarms. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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17 pages, 974 KiB

Open AccessArticle

Development of A Nested-MultiLocus Sequence Typing Approach for A Highly Sensitive and Specific Identification of Xylella fastidiosa Subspecies Directly from Plant Samples

by Sophie Cesbron, Enora Dupas, Quentin Beaurepère, Martial Briand, Miguel Montes-Borrego, Maria del Pilar Velasco-Amo, Blanca B. Landa and Marie-Agnès Jacques

Agronomy 2020, 10(8), 1099; https://doi.org/10.3390/agronomy10081099 - 29 Jul 2020

Cited by 12 | Viewed by 4640

Abstract

Identification of sequence types (ST) of Xylella fastidiosa based on direct MultiLocus Sequence Typing (MLST) of plant DNA samples is partly efficient. In order to improve the sensitivity of X. fastidiosa identification, we developed a direct nested-MLST assay on plant extracted DNA. This [...] Read more.

Identification of sequence types (ST) of Xylella fastidiosa based on direct MultiLocus Sequence Typing (MLST) of plant DNA samples is partly efficient. In order to improve the sensitivity of X. fastidiosa identification, we developed a direct nested-MLST assay on plant extracted DNA. This method was performed based on a largely used scheme targeting seven housekeeping gene (HKG) loci (cysG, gltT, holC, leuA, malF, nuoL, petC). Samples analyzed included 49 plant species and two insect species (Philaenus spumarius, Neophilaenus campestris) that were collected in 2017 (106 plant samples in France), in 2018 (162 plant samples in France, 40 plant samples and 26 insect samples in Spain), and in 2019 (30 plant samples in Spain). With the nested approach, a significant higher number of samples were amplified. The threshold was improved by 100 to 1000 times compared to conventional PCR. Using nested-MLST assay, plants that were not yet considered hosts tested positive and revealed novel alleles in France, whereas for Spanish samples it was possible to assign the subspecies or ST to samples considered as new hosts in Europe. Direct typing by nested-MLST from plant material has an increased sensitivity and may be useful for epidemiological purposes. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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Review

Jump to: Research, Other

16 pages, 1031 KiB

Open AccessReview

Unravelling the Pathogenesis and Molecular Interactions of Liberibacter Phytopathogens with Their Psyllid Vectors

by Poulami Sarkar and Murad Ghanim

Agronomy 2020, 10(8), 1132; https://doi.org/10.3390/agronomy10081132 - 4 Aug 2020

Cited by 9 | Viewed by 4514

Abstract

Insect-borne bacterial pathogens pose a global economic threat to many agricultural crops. Candidatus liberibacter species, vectored by psyllids (Hemiptera: psylloidea), are an example of devastating pathogens related to important known diseases such as Huanglongbing or the citrus greening disease, Zebra chip disease, and [...] Read more.

Insect-borne bacterial pathogens pose a global economic threat to many agricultural crops. Candidatus liberibacter species, vectored by psyllids (Hemiptera: psylloidea), are an example of devastating pathogens related to important known diseases such as Huanglongbing or the citrus greening disease, Zebra chip disease, and carrot yellowing, along with vegetative disorders in umbellifers. Studies on liberibacter–plant interactions have gained more focus in disease control over the last few decades. However, successful and sustainable disease management depends on the early disruption of insect–pathogen interactions, thereby blocking transmission. Recent knowledge on the liberibacter genomes and various omics approaches have helped us understand this host–pathogen relationship, despite the complexity associated with the inability to culture these bacteria. Here, we discuss the cellular and molecular processes involved in the response of insect-host immunity, and the liberibacter-associated pathogenesis mechanisms that involve virulence traits and effectors released to manipulate the insect–host defense mechanism for successful transmission. Understanding such mechanisms is an important milestone for developing sustainable means for preventing liberibacter transmission by psyllids. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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2 pages, 209 KiB

Open AccessCorrection

Correction: Gorris et al. Detection and Diagnosis of Xylella fastidiosa by Specific Monoclonal Antibodies. Agronomy 2021, 11, 48

by María Teresa Gorris, Antonio Sanz, Javier Peñalver, María M. López, Mario Colomer and Ester Marco-Noales

Agronomy 2023, 13(7), 1826; https://doi.org/10.3390/agronomy13071826 - 10 Jul 2023

Viewed by 811

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

23 pages, 4900 KiB

Open AccessEditor’s ChoicePerspective

Fusarium Wilt of Bananas: A Review of Agro-Environmental Factors in the Venezuelan Production System Affecting Its Development

by Barlin O. Olivares, Juan C. Rey, Deyanira Lobo, Juan A. Navas-Cortés, José A. Gómez and Blanca B. Landa

Agronomy 2021, 11(5), 986; https://doi.org/10.3390/agronomy11050986 - 15 May 2021

Cited by 63 | Viewed by 13697

Abstract

Bananas and plantains (Musa spp.) are among the main staple of millions of people in the world. Among the main Musaceae diseases that may limit its productivity, Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. cubense (Foc), has been [...] Read more.

Bananas and plantains (Musa spp.) are among the main staple of millions of people in the world. Among the main Musaceae diseases that may limit its productivity, Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. cubense (Foc), has been threatening the banana industry for many years, with devastating effects on the economy of many tropical countries, becoming the leading cause of changes in the land use on severely affected areas. In this article, an updated, reflective and practical review of the current state of knowledge concerning the main agro-environmental factors that may affect disease progression and dissemination of this dangerous pathogen has been carried out, focusing on the Venezuelan Musaceae production systems. Environmental variables together with soil management and sustainable cultural practices are important factors affecting FW incidence and severity, excluding that the widespread dissemination of Foc, especially of its highly virulent tropical race 4 (TR4), is mainly caused by human activities. Additionally, risk analysis and climatic suitability maps for Foc TR4 in Venezuela have been developed. Although currently there are no effective management solutions available for FW control, this perspective provides an overview on the influence that environmental and agricultural variables would have on FW incidence and severity, giving some insight into management factors that can contribute to reducing its detrimental effects on banana production and how climate change may affect its development. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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14 pages, 2493 KiB

Open AccessEditor’s ChoicePerspective

Landscape Epidemiology of Xylella fastidiosa in the Balearic Islands

by Diego Olmo, Alicia Nieto, David Borràs, Marina Montesinos, Francesc Adrover, Aura Pascual, Pere A. Gost, Bàrbara Quetglas, Alejandro Urbano, Juan de Dios García, María Pilar Velasco-Amo, Concepción Olivares-García, Omar Beidas, Andreu Juan, Ester Marco-Noales, Margarita Gomila, Juan Rita, Eduardo Moralejo and Blanca B. Landa

Agronomy 2021, 11(3), 473; https://doi.org/10.3390/agronomy11030473 - 4 Mar 2021

Cited by 39 | Viewed by 4946

Abstract

Xylella fastidiosa (Xf) is a vascular plant pathogen native to the Americas. In 2013, it was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This finding prompted mandatory surveys across Europe, successively revealing that [...] Read more.

Xylella fastidiosa (Xf) is a vascular plant pathogen native to the Americas. In 2013, it was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This finding prompted mandatory surveys across Europe, successively revealing that the bacterium was already established in some distant areas of the western Mediterranean. To date, the Balearic Islands (Spain) hold the major known genetic diversity of Xf in Europe. Since October 2016, four sequence types (ST) belonging to the subspecies fastidiosa (ST1), multiplex (ST7, ST81), and pauca (ST80) have been identified infecting 28 host species, including grapevines, almond, olive, and fig trees. ST1 causes Pierce’s disease (PD) and together with ST81 are responsible for almond leaf scorch disease (ALSD) in California, from where they were introduced into Mallorca in around 1993, very likely via infected almond scions brought for grafting. To date, almond leaf scorch disease affects over 81% of almond trees and Pierce’s disease is widespread in vineyards across Mallorca, although producing on average little economic impact. In this perspective, we present and analyze a large Xf-hosts database accumulated over four years of field surveys, laboratory sample analyses, and research to understand the underlying causes of Xf emergence and spread among crops and wild plants in the Balearic Islands. The impact of Xf on the landscape is discussed. Full article

(This article belongs to the Special Issue Diagnosis, Population Biology and Management of Vascular Diseases)

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