Mexican Journal
of Phytopathology

• Open access
• Scientific Article

Morphological characterization, phylogeny and pathogenesis of Setophoma terrestris causing corky and pink roots of tomato (Solanum lycopersicum) in Sinaloa, Mexico

byAna María López López, Juan Manuel Tovar Pedraza, Josefina León Félix, Raúl Allende Molar, Nelson Bernardi Lima, Isidro Márquez Zequera, Raymundo Saúl García Estrada*

Received: 27/September/2023 – Published: 13/February/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2309-5

Abstract Background/Objective. Tomato (Solanum lycopersicum) is one of Mexico’s main crops. In the years 2017 and 2018, symptoms of corky and pink roots were observed with an incidence of 10 to 20% in Culiacan, Sinaloa, Mexico. In the foliage, plants presented a generalized chlorosis, with stunted growth and senescence in the leaves. In the roots, brown and pink lesions were formed, as well as a corky texture. The objective of this study was to morphologically and molecularly characterize fungal isolates associated to corky and pink root in tomato orchards in Culiacan, Sinaloa, as well as to evaluate their pathogenicity.

Materials and Methods. Monoconidial isolates were obtained and they were identified as Setophoma terrestris, based on their morphological characteristics. To confirm the identity, the area of the internal transcribed spacers (ITS) of the rDNA was amplified and sequenced, along with a fragment of the gene 28S of the rRNA (LSU).

Results. Using the sequences obtained, a phylogenetic tree was created using the Bayesian Inference and it was found that the sequences were grouped with the ex–type sequences of Setophoma terrestris. The pathogenicity of the isolates was verified by inoculating mycelial discs into the root of 10 one-month-old tomato seedlings. The roots of the seedlings inoculated with PDA discs without mycelium served as a control. Thirty days after inoculation, corky and pink root symptoms appeared, whereas the roots of control plants remained healthy

Conclusion. According to the morphological characterization, the molecular identification and the pathogenicity tests, Setophoma terrestris was confirmed to be the causal agent of corky and pink root in agricultural tomato orchards in Culiacan, Sinaloa.

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Figure 1. Location of the sites of recollection of plants with corky root symptoms in agricultural systems with tomato production in the valley of Culiacan, Sinaloa. Site 1 (24°42’56.58”N, 107°26’42.86”W), Site 2 (24°35’21.67”N, 107°24’56.50”W), Site 3 (24°46’2.77”N, 107°32’51.30”W), Site 4 (24°48’47.44”N, 107°39’26.19”W) and Site 5 24°32’34.07”N, 107°26’44.93”W)

Figure 2. Symptoms of corky and pink roots in tomato. A–C) Chlorosis, deficient growth and senescence in plants. D–F) Dark brown lesions on the root, with swelling, a corky texture and a pink color

Figure 3. Colonies and asexual reproductive structures of Setophoma terrestris. A) Colony of S. terrestris in a V8A medium with 7 days of growth. B) Colony growth on the reverse of the dish. D) Pycnidium. D) Setae. E–F) Biguttulate conidia.

Figure 4. Bayesian Tree obtained with combined data from sequences ITS and LSU. The tree shows the phylogenetic relations of the Setophoma species. The Bayesian posterior probability values of over 0.70 are shown in the nodes. The species Pseudopyrenochaeta lycopersici was used as an external group and the scale bar indicates the number of expected changes per site.

Figure 5. Pathogenicity tests in tomato plants. A–B) Tomato plants of the 8444 variety inoculated with S. terrestris and showing symptoms of yellowing. C) Corky root symptom 30 days after inoculation with S. terrestris. D) Colony obtained from the in vitro reisolation of S. terrestris.

Table 1. Information of fungal isolates and GenBank accession numbers of Setophoma species used in the phylogeneti analysis.

Table 2. Measurements of asexual structures in Setophoma terrestres isolates obtained from tomato plants.

• Open access
• Scientific Article

Genus Orthotospovirus in Costa Rica: A Central American case

byMauricio Montero Astúa*, Natasha Dejuk Protti, David Bermúdez Gómez, Elena Vásquez Céspedes, Laura Garita Salazar, Federico J. Albertazzi, Scott Adkins, Lisela Moreira Carmona

Received: 23/August/2023 – Published: 28/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-6

Abstract Background/Objective. The Orthotospovirus genus encompasses a range of economically significant and emerging plant viruses that affect a variety of crops globally. While the prevalence and characteristics of these phytopathogenic viruses are extensively documented in North and South America, their presence in Central America remains comparatively underexplored. This study focuses on Costa Rica, strategically positioned at the nexus of North and South America, to enhance our understanding of Orthotospovirus in this region.

Materials and Methods. We analyzed 295 plant samples using enzyme-linked immunosorbent assay (ELISA) to test for the presence of INSV, IYSV, TSWV, and the GRSV/TCSV serogroup. Additionally, a subset (20 samples) underwent further scrutiny through reverse transcription-polymerase chain reaction (RT-PCR) employing both universal and species-specific primers.

Results. Our ELISA results indicated the absence of TSWV and the GRSV/TCSV serogroup. However, the presence of INSV in Costa Rica was substantiated through ELISA, RT-PCR, and partial sequencing, revealing its prevalence in both open-field and greenhouse environments. Despite previous diagnostic reports suggesting the presence of TSWV in Costa Rica, our study did not detect this virus. RT-PCR analysis with degenerate primers also found no evidence of other Orthotospovirus species in our samples. The identification of a dominant INSV haplotype, along with three additional variants, suggests the likelihood of at least two independent virus introductions into the region.

Conclusion. These findings underscore the necessity for more comprehensive surveys and research on Orthotospoviruses in Central America to better understand their epidemiology and impact on agriculture.

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Figure 1. Representation of primer pairs annealing positions in reference to the complete genome of Impatiens necrotic spot virus; accession numbers in parenthesis for each genome segment. Overlapping among primers and the final partial sequences (gray rectangles) obtained herein with corresponding expected size (bp). Base pair values under each primer represent the positions of the first and last nucleotide of the corresponding amplicon in the reference genome

Figure 2. Diverse Symptoms of Impatiens necrotic spot virus (INSV) in Multiple Hosts Confirmed by ELISA and RT-PCR/Sequencing. A: Necrotic concentric rings on Impatiens (Impatiens sp.) T031. B, C: Chlorotic rings and spots on Snapdragons (Antirrhinum majus) T057. D: Chlorotic and necrotic striate on orchid leaves T024. E, F: Chlorotic mosaic on Amaryllis (Hippeastrum sp.) T161 and Iris (Iris sp.) T184. G: Necrotic concentric rings on Coleus (Plectranthus scuttellarioides) T157. H: Chlorotic patterns on Basil (Ocimum basilicum) T156. I, M: Chlorotic concentric ring patterns on Sweet Pepper (Capsicum annuum) leaves T250 and T092. J, K, L: Uneven ripening, ring patterns, and deformation on Sweet Pepper fruits T092, T107, T094. N, O: Chlorotic patterns, rings, and uneven surface on Tomato (Solanum lycopersicum) fruits T263 and T303.

Figure 3. Long-Term Detection of impatiens necrotic spot and tomato spotted wilt viruses by ELISA. This graph presents the frequency of detection for both Impatiens necrotic spot virus and Tomato spotted wilt virus over a 23.5-year period (2000 to July 2023). The data, derived from samples submitted to the diagnostic services at the Cellular and Molecular Biology Research Center, University of Costa Rica, illustrate the temporal trends and occurrence patterns of these viruses in Costa Rica.

Figure 4. Haplotype Network Graph of Impatiens Necrotic Spot Virus. This graph is a haplotype network inferred using the TCS method, based on a 261 bp sequence alignment of the nucleocapsid protein ORF (S[N] segment) of Impatiens necrotic spot virus. The network includes data from 81 isolates, visually representing the genetic relationships and diversity among the different haplotypes of the virus.

Figure 5. Comprehensive phylogenetic analysis of impatiens necrotic spot virus isolates. This figure illustrates a phylogenetic tree constructed from an alignment of concatenated sequences (2945 positions) encompassing regions of the nucleocapsid [S(N)], glycoprotein precursor [M(G)], movement protein [M(NSM)], and viral polymerase [L(L)] ORFs. The tree includes isolates from various countries, identified by ISO 3166-1 three- letter codes: CHN (China), ITA (Italy), KOR (South Korea), and USA (United States of America). For Costa Rican isolates, additional distinct letter codes in parenthesis signify separate geographic locations. The analysis, executed in MEGA X, utilized the Maximum Likelihood method with a Tamura-3-parameter model and a gamma-distributed rate of variation in nucleotides (+G), involving 2000 permutations. The scale bar indicates the number of nucleotide substitutions per site.

Table 4. Partial nucleotide sequences and virus identity determined for a subset of INSV ELISA-positive samples

Table 1. Samples collected from five provinces of Costa Rica to analyze the presence of species of Orthotospvirus

Table 2. Primer pairs and thermocycle profiles used for the detection of Orthotospoviruses

Table 3. Number of total and positive samples per plant species tested by ELISA to detect three Orthotospoviruses in Costa Rica.

• Open access
• Scientific Article

Virome of the vegetable prickly pear cactus in the central zone of Mexico

byCandelario Ortega Acosta, Daniel L. Ochoa Martínez*, Reyna I. Rojas Martínez, Cristian Nava Díaz, Rodrigo A. Valverde

Received: 31/July/2023 – Published: 27/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-2

Abstract Background/Objective. In this study, the ability of high-throughput sequencing (HTS) to detect viruses in vegetable prickly pear cactus was exploited.

Materials and Methods. Samples from State of Mexico (EDMX), Hidalgo, and Morelos, as well as Mexico City (CDMX), were analyzed.

Results. In the sample from EDMX, the genomes of Opuntia virus 2 (OV2, genus Tobamovirus) and Cactus carlavirus 1 (CCV-1, genus Carlavirus) were detected and recovered. In the sample from CDMX, in addition to OV2 and CCV-1, a new viroid and potexvirus were detected. The former has a circular RNA genome with a length of 412 nt for which the name “Opuntia viroid I” (OVd-I) is proposed. The primary structure of this viroid showed a nucleotide sequence identity of less than 80% with any of the currently known viroids and a phylogenetic relationship with the genus Apscaviroid (Family Pospiviroidae) with which it shares conserved structural motifs.

Conclusion. The new potexvirus was named Opuntia potexvirus A (OPV-A), whose viral replicase sequence has a 77.7 % amino acid identity with Schlumbergera virus X. Finally, CCV-1 was detected in 93 (72 %) of 129 vegetable prickly pear cactus samples collected in the four entities.

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Figure 1. Symptoms associated with virosis in vegetable prickly pear cactus cladodes. (A-D) Samples of prickly pear cactus collected in Mexico City, Milpa Alta Borough, (E) Prickly pear cactus sample collected in the State of Mexico, Otumba Municipality, (F) Healthy prickly pear cactus sample from the State of Mexico.

Figure 10. Maximum Likelihood phylogenetic tree of the Alphaflexiviridae family based on amino acid se- quences of the coat protein; the Opuntia potexvirus A sequence is highlighted in bold. Tree colors represent different genera within this family. Circles on branches indicate UFBoot support values >70%.

Figure 11. Predicted secondary structure using the UNAFold web server (UNAFold tool available online: www. mfold.org) for OVd-I. Highlighted are the sites forming the terminal conserved region (TCR) at positions 16 to 26 and the central conserved region (CCR) at positions 84 to 100 and 313 to 329

Figure 12. Maximum Likelihood phylogenetic tree of the Pospiviroidae and Avsunviroidae families based on nucleotide sequences of complete genomes from representative species of different genera. The sequence obtained from OVd-I is highlighted in bold. Various colors represent viroid genera. Circles on branches indicate UFBoot support values >50%.

Figure 13. Pairwise identity frequency distribution obtained using the Sequence Demarcation Tool (SDT) (Muhire et al., 2014) from complete genome sequences of Pospiviroidae family species to support the demarcation of Opuntia viroid I as a new species

Figure 14. Viral particles in the form of rigid rods (®) and flexible filaments (®) of varying lengths were observed through transmission electron microscopy in vegetable prickly pear cactus exhibiting irregular yellow patterns, yellow rings, mosaic patterns, and chlorotic spots around the spines, employing the “leaf dip” technique

Figure 2. (A) Read coverage across the genome of the OV2-Edo-Mex isolate and the percentage of guanine-cytosine content, (B) Genomic map of OV2-Edo-Mex. The arrow indicates the termination codon site of the complete 128 kDa protein, with readthroughs

Figure 3. (A) Read coverage across the genome of the OV2-CDMX isolate and the percentage of guanine-cytosine content. (B) Genomic map of OV2-CDMX. The arrow indicates the termination codon site of the complete 128 kDa protein, with readthroughs.

Figure 4. Maximum Likelihood phylogenetic tree of the Tobamovirus genus showing the relationships between genomes obtained in this study (in bold) for OV2 and those of previously reported isolates. Different colors represent botanical families as natural hosts where each virus has been reported. Circles on branches indicate UFBoot support values > 70%.

Figure 5. (A) Read coverage across the genome of the CCV-1-Edo-Mex isolate and the percentage of guanine-cytosine content. (B) Genome organization of CCV1-Edo-Mex, depicting six open reading frames and their corresponding products. RNA-dependent RNA polymerase (RdRp); coat protein (CP); nucleic acid-binding protein (NB); triple gene block (TGB)

Figure 6. Maximum Likelihood phylogenetic tree of complete nucleotide sequences of CCV-1 genomes from this study (in bold), along with other isolates, and various species within the Carlavirus genus. Apricot vein clearing associated virus, Prunevirus genus, was used as an outgroup. Circles on branches indicate UFBoot support values > 50%.

Figure 7. (A) Read coverage across the genome of Opuntia potexvirus A (OPV-A) and guanine/ cytosine percentage. (B) Genome organization of OPV-A, displaying five open reading frames and their corresponding products: RdRp, viral replicase; TGB, triple gene block; CP, coat protein.

Figure 8. Matrix of amino acid identity percentage for the coat protein (A) and viral replicase (B) of species within the Potexvirus genus closest to Opuntia potexvirus A (in bold)

Figure 9. Maximum Likelihood phylogenetic tree of the Alphaflexiviridae family based on viral replicase amino acid sequences; the Opuntia potexvirus A sequence is highlighted in bold. Tree colors rep- resent different genera within this family. Circles on branches indicate UFBoot support values >70%

Table 1. Primers used in RT-PCR assays for the validation of viruses/viroids detected in the HTS data from two vegetable prickly pear cactus libraries

Table 2. Comparison of the complete or partial genome of the viruses identified through HTS in the two vegetable prickly pear cactus libraries with the most closely related reference sequence from GenBank.

Table 3. Result of Blastx analysis for potentially present viruses in the CDMX-1 library, confirmed through RT-PCR and sequencing

Table 4. Detection of CCV-1 in four vegetable prickly pear cactus producing states in Mexico

• Open access
• Review Article

Aspergillus oryzae: An opportunity for agriculture

byKaren Berenice García Conde, Ernesto Cerna Chávez, Yisa María Ochoa Fuentes*, Jazmín Janet Velázquez Guerrero

Received: 23/February/2023 – Published: 14/November/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2302-2

Abstract Aspergillus oryzae is a filamentous fungus capable of degrading various substances employing enzymes, which is why it is widely used in the biotechnological industry, pharmaceutical products, enzymes for industrial use, bleaching agents, anti-pollution textile treatments. However, few works focus on these microorganism’s field applications. This manuscript reviews the potentially beneficial applications of A. oryzae and some by-products in agriculture as biological control, growth inducer, and bioremediation for soils contaminated with heavy metals.

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Figure 1. Morphology of A. oryzae; A) Parts and structures of the fungus (Adapted from “Structure of Aspergillus spp.”, 2023), B) A. oryzae planted in a PDA medium and C) Growth of A. oryzae in steamed rice (köji)

Figure 2. Areas of application of Aspergillus oryzae

Figure 3. Characteristics and basics of kojic acid based on reports by Phasha et al. (2022) and Siddiquee (2018)

Table 1. Use of A. oryzae as a growth enhancer, pest control agent and bioremediator od contaminated soils

Table 2. Activity of bioactive substances produced by A. oryzae against plant pathogens.

• Open access
• Phytopathological note

Etiology of rhizome rot of asparagus (Asparagus officinalis) in Atenco, Mexico State

byJuan Agustin Gonzalez Cruces*, José Sergio Sandoval Islas, Cristian Nava Díaz, Maricarmen Sandoval Sánchez

Received: 30/November/2023 – Published: 16/November/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2211-1

Abstract Background/Objective. The objective of this research was to identify the causal agent of asparagus rhizome rot, as well as evaluate different inoculation methods and the severity of the isolates.

Materials and Methods. Sampling was carried out in five producing plots Atenco, Edo. from Mexico. Five isolates of Fusarium spp. were selected. (one per plot) to perform pathogenicity tests. Three isolates were selected for their colonization characteristics for severity tests with different inoculation methods: Immersion for 12 h, immersion for 30 min and inoculation by contact with absorbent paper soaked in 1 mL of inoculum. Concentrations of 1x106 conidia mL-1 were used. 10 rhizomes were used per treatment and 10 rhizomes without inoculation. To determine the severity, photographs (in GIMP®) of the rhizome were analyzed seven days after inoculation. The isolates were molecularly identified with ITS4/ ITS5, EF688/EF1521 and TUBT1/BT2B.

Results. Fusarium prolifetatum was morphologically and molecularly identified in the three isolates. The P3DR isolate was the most severe (14.6%), followed by P5DR (13.9%) and P1SIR (11.6%).

Conclusion. The most effective inoculation method was immersion for 30 min. They were registered in the NCBI Gene Bank with accessions ON738484 (P3DR), ON973801 (P5DR) and ON738483 (P1SIR). This is the first report of F. prolifetatum in the Edo. from Mexico.

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Figure 1. Symptoms of wilting in 6-year-old asparagus crop. A) Asparagus crop with symptoms of generalized decline; B) Plant with symptoms of generalized wilting; C) Plant with symptoms of initial wilting; D) Rotting of the rhizome caused by Fusarium proliferatum; E) Basal part of the stem with symptoms of F) Basal part of the stem with vascular bundle blockage.

Figure 2. F. proliferatum isolations used for the pathogenicity tests via different inoculation methods. A) Concatenated phylogenetic tree of isolates ON738483 (PISIR), ON738484 (P3DR) and ON973801 (P5DR) with the primers ITS 4-ITS5, EF688-EF1521, TUB T1-BT2B. B) Rhizome colonization by isolate P1SIR, C) Mycelial growth of Fusarium on the front and back of PDA medium after 7 days of growth, D) Macro and microconidia at 40X. E) Rhizome colonization by isolation P3DR, F) Mycelial growth of Fusarium on the front and back of PDA medium after 7 days of growth, G) Macro and microconidia at 40X. H) Rhizome colonization by isolate P5DR, I) Mycelial growth of Fusarium on the front and back of PDA medium after 7 days of growth, J) Macro and microconidia at 40X

Figure 3. Inoculation methods with Fusarium isolations in asparagus rhizomes. A) Immersion of rhizome for 12 h; B) Inoculation with filter paper; C) Immersion of rhizome for 30 min, showing the rhizome suspended by disinfected mesh and moist filter paper inside a sterile square box; D) Rhizome by the immersion method for 12 h E) Rhizome by the inoculation method with filter paper F) Rhizome by the immersion method for 30 minutes

Figure 4. Percentage of severity of three F. proliferatum isolates in asparagus under three inoculation methods, and a control, not inoculated.

Table 1. Asparagus plots sampled with symptoms of decline and wilting with low technology (gravity irrigation and without mulching) inorganic agronomic management and the phenological stage of flowering-fruiting, in Atenco, State of Mexico.

Table 2. Primers used, sequence, region of the amplified gene, amplicon size, and PCR conditions for the genomic

• Open access
• Phytopathological note

Diagrammatic scale to evaluate the severity of gray mold (Botrytis cinerea) in pomegranate

byAlberto Patricio Hernández, Yuridia Mercado Flores*, Alejandro Téllez Jurado, María del Rocío Ramírez Vargas, Andrés Quezada Salinas

Received: 30/October/2022 – Published: 15/June/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2302-9

Abstract The aim of this study was to design and validate a diagrammatic scale to estimate the severity of gray mold induced by Botrytis cinerea in pomegranate cultivation. A total of 120 healthy and diseased fruits with varying degrees of affliction were collected from orchards with active production located in the municipalities of Chilcuahutla and Taxquillo in the state of Hidalgo, Mexico (20° 18’ 11’’ N, 99° 14’ 23’’ W, 20° 32’ 01’’ N, 99° 20’ 03’’ W, respectively). From these, 60 were selected to determine the severity percentage, according to a 6-class scale (Class 0 = 0%, Class 1 = >0% - 5% - 10%, Class 2 = >10% - 25% - 50%, Class 3 = >50% - 75% - 85%, Class 4 = >85% - 90% - 95%, and Class 5 = >95% - 100%), using the 2LOG software. With the obtained data, representative images were selected to build the diagrammatic scale using Adobe Photoshop. The accuracy (r2), precision (β0), and reproducibility (β1) were verified by simple linear regression applied to the data obtained by 12 evaluators with and without experience in the observation of plant diseases. As a result, values of r2 of 0.42 and 0.85 were obtained, without and with the use of the scale, respectively, which confirmed that this tool is suitable to evaluate the severity of the disease accurately and reproducibly.

• Open access
• Phytopathological note

In vitro antagonism of Trichoderma against Rhizoctonia solani

byJesús Orlando Pérez González, Sergio Gavino Ramírez Rojas, Ramiro Rocha Rodríguez, Katya Ornelas Ocampo, Jorge Miguel Vázquez Alvarado, Filogonio Jesús Hernández Guzmán, Mariel Garduño Audelo*

Received: 30/October/2022 – Published: 15/June/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2304-2

Abstract Trichoderma spp., is a highly efficient antagonist of root pathogens, such as Rhizoctonia solani, which causes loss in many crops. The aim of this research was to evaluate in vitro the antagonistic capacity of T. viride, T. koningii, T. harzianum and Trichoderma spp. isolates against R. solani from a potato crop. In confrontation tests, all Trichoderma isolates were classified as antagonists class 2 according to Bell scale, where T. harzianum and T. koningii showed more than 60% inhibition of the radial growth of R. solani at 120 h. In the interaction between T. harzianum and Trichoderma spp. with R. solani, as mycoparasitism strategy, vacuolization, lysis, coiling, and penetration were demonstrated, the last two were present in all Trichoderma isolates evaluated.

• Open access
• Review Article

Considerations about interference RNA for the control of fungal diseases in Mexican and Latin American agriculture

byOsvaldo Jhosimar Couoh Dzul, Karla Gisel Carreón Anguiano, Blondy Canto Canché*

Received: 30/October/2022 – Published: 15/June/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2210-5

Abstract The control of phytopathogens is key for food security. In the last decade, the use of interference RNA (iRNA) has been proposed as a technological tool for controlling diseases and pests in agriculture. Although different approaches have been described, such as the use of “Host-Induce Gene Silencing” (HIGS) and “Virus-Induce Gene Silencing” (VIGS), more recently a non-transgenic and environmentally friendly approach has emerged, called “Spray -Induce Gene Silencing” (SIGS), which uses double-stranded “naked” RNA (dsRNA). This review discusses recent reports on the use of dsRNA, especially SIGS, to control phytopathogenic fungi; emphasizing factors such as efficacy, safety in terms of human health and its stability in the environment. It also focuses on important phytosanitary problems in Mexico and Latin America that can be addressed with SIGS. This review concludes that SIGS technology has real potential to be used to control phytopathogenic fungi on plants in the field and on postharvest fruits. At the end, the critical tasks and the lines of research that must be carried out to promote the SIGS to make it a reality are considered.

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• Scientific Article

Pathogenicity, virulence and in vitro sensitivity of Elsinoe perseae (= Sphaceloma perseae) isolates to different fungicides

byEdna Esquivel Miguel, José Luciano Morales García*, Martha Elena Pedraza Santos, Ana Tztzqui Chávez Bárcenas, Soledad García Morales, Samuel Pineda Guillermo

Received: 01/May/2023 – Published: 24/August/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2302-3

Abstract Elsinoe perseae (= Sphaceloma perseae) is the causal agent of the Mancha purpura or scab in avocado (Persea americana). In this study, the pathogenicity and virulence of E. perseae isolates from different agroecologicalproducing areas of Michoacán, Mexico will be reduced. For this, nursery plants with avocado fruits of Flor de María and Méndez varieties were used. On the other hand, the in vitro sensitivity of chemical fungicides (Azoxystrobin, thiabendazole, Pyraclostrobin, Cyprodinil + Fludioxonil and Azoxystrobin + Propiconazole) and authorized for use in orchards with organic management (copper sulfate, copper gluconate, copper oxychloride and the plant extract Larrea tridentata). The observed symptoms of Mancha purpura in the inoculated fruits were corroborated with those described for E. perseae in avocado. Inoculated fruits Flor de María variety shows the highest susceptibility to the pathogen. The isolates of E. perseae presented different degrees of virulence. The isolates showed different in vitro sensitivity values to the fungicides evaluated in the experiment. The pathogen showed the most sensitivity in vitro to chemical fungicides: thiabendazole and Azoxystrobin + Propiconazole (100% inhibition), and to those authorized in orchards with organic management: L. tridentata and copper oxychloride (on average 58% inhibition).

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• Scientific Article

Effect of adjuvants, fungicides and insecticides on the growth of Trichoderma koningiopsis Th003

byYimmy Alexander Zapata Narváez*, Blanca Lucia Botina Azain

Received: 01/May/2023 – Published: 24/August/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2305-1

Abstract The effect of 44 agrochemicals (fungicides, insecticides and adjuvants) on the mycelial growth and germination conidia of Trichoderma koningiopsis Th003 was determined by seeding of 5 mm discs of fungal mycelium in Sabouraud agar supplemented with each agrochemical and seeding of conidia suspended in solutions of agrochemicals in water agar. For the adjuvants, their effect on the phyllospheric establishment of T. koningiopsis Th003 was determined by following their population in cape gooseberry leaflets inoculated with the fungus suspended in them. Eight fungicides did not inhibit the fungus mycelial growth or the conidia germination. Fenhexamid - Tebuconazole, Flutriafol and Kasugamicina inhibited it between 34 and 48% without affecting germination, Thiram - Pyrimethanil, Prochloraz, Tiabendazol, Spiroxamina and Triadimenol - Tebuconazole inhibited the growth and Thiram - Pyrimethanil and Dodine did not allow conidia germination. Insecticides and adjuvants presented an inhibition of up to 70% but did not affect the conidia germination. No negative effects of the adjuvants on the phyllosphere establishment of T. koningiopsis Th003 were observed, recovering from the treatments approximately 1x103 CFU g-1.