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by Lorena Uribe Lorío* ,Lidieth Uribe ,César Rodríguez ,Luis Felipe Aráuz
Accepted: 05/January/2023 – Published: 26/February/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2305-5
Abstract Objetive/Background. The aim of this was to assess the diversity and antibiotic resistance of bacteria isolated from 19 crops with bacterial infection symptoms.
Materials and Methods. This collection was identified using 16S rRNA gene sequencing and the Biolog system. Susceptibility and minimum inhibitory concentration (MIC) for streptomycin, tetracycline, and gentamicin were determined using disk diffusion and E-test methods, respectively.
Results. A total of 55 species belonging to 20 bacterial genera were identified, with Pseudomonas, Serratia, Pantoea, and Stenotrophomonas being the most abundant. Approximately 27% of the isolates were categorized as pathogenic through the hypersensitivity reaction test, including phytopathogenic species like Pseudomonas syringae, P. cichorii, Pantoea anthophila, P. stewartii, Stenotrophomonas maltophilia, Dickeya oryzae, Erwinia billingiae, Pectobacterium aroidearum, and Enterobacter cloacae subsp. dissolvens. Resistance to at least one antibiotic was detected in 60% of isolates from 17 crops, with tomatoes, heart of palm, and lettuce exhibited the highest proportion of resistant bacteria (>80%). Streptomycin resistance was most common (35%), followed by tetracycline (28%) and gentamicin (9%).
Conclusion. The findings indicate the presence of antibiotic resistance in saprophytic and pathogenic bacteria associated with 17 out of 19 assessed crops, posing risks to the environment, phytosanitary conditions, and public health
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Figure 1. Symptoms of bacterial infection from which the bacterial collection were isolated. A. Leaf spot in Boston Lettuce, B. Soft rot in Iceberg Lettuce, C. Necrotic spot on Tomato. D. Soft rot in Celery. E. Soft rot in Pepper. F. Soft rot in Dracaena. G. Soft rot in Pumpkin. H. Angular necrosis in Cabbage. I. Fruit spot in Mango.
Figure 2. Cladograma construido con el método del vecino más cercano a partir de 70 secuencias parciales del gen ARNr 16S de bacterias aisladas de lesiones en plantas y secuencias de cepas de referencia. Se evaluó la topología del árbol realizando 1 000 remuestreos y se utilizó la secuencia de Bacillus subtilis como grupo externo. Los símbolos en el exterior del árbol indican los aislamientos clasificados como resistentes a Estreptomicina, Tetraciclina y Gentamicina y sus combinaciones (círculos) y aquellos con Reacción hipersensible positiva (triángulos)Cladogram constructed using the nearest neighbor method from 70 partial sequences of the 16S rRNA gene of bacteria isolated from plant lesions and sequences of reference strains. The tree topology was assessed through 1,000 resamplings, with the sequence of Bacillus subtilis used as an outgroup. Symbols on the outer part of the tree indicate isolates classified as resistant to Streptomycin, Tetracycline, and Gentamicin, as well as their combinations (circles), and those with a positive Hypersensitive Reaction (triangles).
Figure 3. A. Halos indicating sensitivity to antibiotics on Oxoid discs for gentamicin and tetracycline, and resistance to streptomycin (absence of a halo) in the Kirby Bauer disk diffusion test. B. Bacteria with a minimum inhibitory concentration (MIC) of 0.25 μg mL-1 for gentamicin, determined by the E-test method. C. Bacteria with a MIC of 32 μg mL-1 for the same antibiotic.
Figure 4. Proportion of bacteria resistant (MIC ≥ 12 μg mL-1) to the antibiotics Streptomycin (Str), Tetracycline (Tet), and Gentamicin (Gent), as well as their combinations, in the analyzed hosts that had more than one isolation
Table 3. Bacterial genera identified and the frequency of bacteria resistant to the antibiotics Streptomycin (Strept), Tetracycline (Tetra), and Gentamicin (Gent)
Table 1. Diversity and antibiotic resistance in bacteria associated with symptoms of bacterial infection in Costa Rican crops
Table 2. Molecular identification and resistance levels to streptomycin, tetracycline, and gentamicin of bacteria associated with infection symptoms in crops collected from 2006-2009 in Costa Rica.
by María José Armenta Rojas ,Norma Ávila Alistac ,María del Carmen Zúñiga Romano ,Gerardo Acevedo Sánchez ,Alfonso Muñoz Alcalá ,Rene Gómez Mercado ,Juan José Coria Contreras ,Diana Gutiérrez Esquivel ,Serafín Cruz Izquierdo ,Ivonne García González ,Oscar Bibiano Nava ,Gustavo Mora Aguilera*
Accepted: 25/December/2024 – Published: 12/February/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2310-7
Abstract Introduction/Objective. Ayocote bean (Phaseolus coccineus) has potential as a source of resistance in breeding programs because it exhibits greater tolerance to plant pathogens than P. vulgaris. However, its sanitary characterization is insipient; therefore, the purpose of this work was to carry out an etiological-epidemiological diagnosis, with emphasis on presumptive symptoms of viral and phytoplasmic organisms, and a typical fungal signs of powdery mildew.
Materials and Methods. A plot (50 x 62 m) of flowering Ayocote bean was selected. It was divided into 80 (8 x 10) quadrats (6 x 6 m) and 720 subquadrats (2 x 2 m). From 25 plants with powdery-mildew-type leaf symptoms, mycelium was collected with adhesive tape for light microscopy observation and taxonomic identification. Length-width measurements were made on 60 conidia. Pure mycelium collected in situ and ex situ from 1-5 leaflets/plant was used for genomic analysis by PCR with universal primers ITS1 and ITS4. Samples were sequenced in Macrogen Inc. Korea. A total of 63 plants and 121 trifoliate leaves with viral and phytoplasmic symptoms were collected by direct sampling. In 88/121 samples, genomic analysis was performed by PCR with universal primers for Potyvirus (1), Begomovirus (2), and Phytoplasmas (1). Sequence editing and analysis were performed in SeqAssem and BLASTn/GenBank. Phylogenetic constructions were developed in Mega 11 with MUSCLE, Maximum Likelihood (ML), and HKY substitution model (1000-Bootstrap). Putative powdery mildew severity (%), flower damage (%), Macrodactylus sp. adult density, and plant vigor (%) were evaluated in 80 quadrats (3subquadrats/quadrat) with App-Monitor®v1.1 configured with a 5-class scale. In GoldenSurfer® v10, Kriging geostatistical analysis was performed to determine the spatial interrelationship between these variables.
Results. Erysiphe vignae was identified as associated with powdery mildew of P. coccineus. The fungus, with hyaline, ovoid to ellipsoid conidia measuring 31.74 ± 0.3419 μm x 15.11 ± 0.1579 μm, without the presence of fibrosin bodies, had 100% genomic homology. This is the first report in Mexico. With average July-August temperature and relative humidity of 16.3 °C (±5.8) and 92.8 % (±10.7), respectively, powdery mildew leaf incidence and severity were 65.3 and 22.7 % (±16.9, range: 0 - 66.5 %), respectively. The most inductive focus (60- 80 % severity) had an aggregate e 4-quadrat pattern (96 m2, lag = 4 and σ2-s = 450). Inoculum dispersal was significantly associated with dominant North-South winds and plant vigor (lag = 4 and σ2-s = 470). Flower damage was inconclusive in its spatial association with powdery mildew and Macrodactylus sp. suggesting uncorrelated events. No Potyvirus, Begomovirus, or Phytoplasmas were detected associated with yellowing, leaf distortion, mosaic, internode shortening, and other symptoms observed in situ. This confirms the relative tolerance/resistance reported for P. coccineus.
Conclusion. E. vignae (Erysiphales: Erysiphaceae) associated with P. coccineus is reported for the first time in Mexico with moderate to intense epidemic level, which indicates its susceptible condition to this fungus. However, negative results for Potyvirus, Begomovirus, and Phytoplasmas, validate the apparent tolerance/ resistance of P. coccineus to these organisms.
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Figura 2. Morphological and genomic identification of powdery mildew in Ayocote bean (Phaseolus coccineus). A. hyaline, ovoid to ellipsoid conidia; B-C. cylindrical and erect conidiophores; D-F. germinating conidia; G. Amplification of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA (~500 bp) of five samples of cenicilla DNA (1-5), two positive PCR controls (+) belonging to the ITS region of Alternaria and Fusarium genera, 1 kb molecular weight marker (M) plus Invitrogen and negative PCR control (-); H. phylogenetic tree performed by Maximum Likelihood (ML) and the Hasegawa-Kishino-Yano substitution model with 1000 Bootstrap replications, based on ITS region of fungal sequences belonging to Erysiphe genus (Table 2). The study sequences are: FAC6, FAC7, FAC8 and FAC9 (red dot). Oidium sp. (accession number: EU377475) was included as outgroup
Figura 3. Presumptive field symptoms of phytoplasma infection in Ayocote bean (Phaseolus coccineus). A. Putative symptoms to phytoplasmas. Including leaf deformation, brown or violet coloration, obvious purplish coloration on veins of back young leaves, stunting, slight yellowing of leaves; B. Examples of six trifoliate leaves showing presumptive symptoms of phytoplasmas, included in PCR diagnosis; C. Agarose gel electrophoresis of 24 samples processed by nested PCR. PCR-amplified positive controls only.
Figura 4. Geostatistical Kriging contour maps and variograms of phytosanitary variables and vigor in Ayocote bean. A. Powdery mildew severity, B. Flower damage, C. Density of Macrodactylus sp. adults and D. Plant canopy. For adult analysis, cumulative of three subquadrants per quadrant was calculated. For the analysis of powdery mildew severity, flower damage, and plant canopy, the maximum damage obtained per quadrant was calculated. Omnidirectional variograms were obtained by the Spherical method. X-axis = distance-lag in quadrants and Y-axis = variance (σ2)
Figure 1. Sampling methodology to identify and assess severity of fungal, presumtive viral/phytoplasmal symptoms, and entomological signs on Phaseolus coccineus. A. 13mpx image at 50m using DJI® Phantom-3 drone, showing quadrantization of experimental plot. Yellow-lines correspond to 6x6 m quadrants, and white-lines to 2x2 m subquadrants. Asterisks indicate randomly selected subquadrants/quadrants; B. Field quadrant marking with wooden-stakes and a slat-net; C. Selection of subquadrant by placing wooden frame 1x1 m for assessment guidance; D. Dotted mosaic symptoms (left) and vein clearing (right), putative to virosis. Plants marked with stakes for traceability samples; E. Generalized yellowing with growth reduction (left), mosaic with leaf deformation (right) presumptive viral; F. Leaf symptom with white fungal mycelial growth putative to powdery mildew; G. Front leaflet showing white mycelial growth. H. Macrodactylus sp. adults, and flowering color morphology of P. coccineus. Note some petals showing small white-spots (see arrows).
Table 1. Primers, sequences, and amplicon size for genomic identification of Potyvirus, Begomovirus, Phytoplasmas and eukaryotic microorganisms in P. coccineus plants exhibiting signs of powdery mildew and putative virus and phytoplasma symptoms.
Table 2. Sequences obtained from the NCBI Genebank used to construct the phylogenetic tree for comparison with amplicon sequences obtained from four samples of powdery mildew fungus present in P. coccineus plants.
by Mauricio Montero Astúa* ,Izayana Sandoval Carvajal ,Lisela Moreira Carmona ,William Villalobos Muller ,Laura Garita Salazar ,Sofía Carvajal Rojas
Accepted: 15/December/2023 – Published: 30/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-3
Abstract Background/Objective. Leaves of the shrub chaya (Cnidoscolus aconitifolius), spinach tree or ‘chicasquil’ (in Costa Rica), are consumed in the Mesoamerican culinary tradition, having its origin in South Mexico and Guatemala. The objective of this work was to verify the viral nature of the observed in a chaya plant disease and to identify the species of the virus.
Materials and Methods. Plant virus detection and identification was achieved by TEM, RT-PCR using degenerated primers to potexviruses, and sequencing. Pathogenicity tests were done by mechanical inoculation using chaya symptomatic tissue, on Nicotiana benthamiana and chaya plants.
Results. We report CsCMV detection in a chaya plant in Costa Rica with mosaic symptoms. Pathogenicity and association of virus and symptoms were demonstrated by mechanical inoculation in Nicotiana benthamiana and chaya plants. We hypothesize this infection corresponds to a recent introduction and discussed how cultural traditions impact the distribution of plant viruses.
Conclusion. The findings confirm the presence of a CsCMV-related virus, previously unreported for Costa Rica, in Cnidoscolus aconitifolius. The results herein highlighted the need to study its distribution and diversity throughout Latin America
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Figure 1. Chaya (Cnidoscolus aconitifolius) sample 20.222, tentative var. ‘Estrella’, with mosaic symptoms and positive for Cassava common mosaic virus (CsCMV) (A). Mechanical inoculation of sample 20.222 on Nicotiana benthamina (B) and chaya, tentatively var. ‘Chayamansa’ (C) showing mosaic symptoms. Stablished cuttings from sample 21.030 in LaFOV-CIBCM greenhouse (D). Leaf morphology of var. ‘Picuda’ (E).
Figure 2. Transmission electron microscope observations of leaf tissue of chaya (Cnidoscolus aconitifolius)
Figure 3. Transmission electron microscope observations of leaf tissue of chaya (Cnidoscolus aconitifolius)
Table 1. Chaya (Cnidoscolus aconitifolius) samples evaluated for viral symptoms and sources of stem cuttings for transmission assays.
Comparison of molecular protocols to detect Tomato brown rugose fruit virus in solanaceae hosts
by Erika J. Zamora Macorra ,Katia Aviña Padilla* ,Rosemarie W Hammond ,Daniel L. Ochoa Martínez
Accepted: 24/November/2023 – Published: 23/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-5
Abstract Background/Objective. The Tomato brown rugose fruit virus (ToBRFV) has emerged as a significant threat to Solanaceae crops, including tomato and pepper. Its presence in Mexico since 2018 has raised concerns about its impact on agricultural production. Early and accurate detection of this pathogen is essential to prevent its spread and mitigate its effects. In Mexico, several molecular techniques are employed for its diagnosis, including endpoint RT-PCR, RT-qPCR, and multiplex RT-qPCR.
Materials and Methods. This research aimed to assess the efficiency of different RNA extraction methods in combination with specific PCR primers for detecting ToBRFV.
Results. Among the methods tested, the CTAB-Trizol RNA extraction protocol combined with nested PCR using primers reported by Dovas et al. (2004) was identified as the most sensitive molecular method for detecting the virus.
Conclusion. This finding highlights the importance of selecting the appropriate combination of extraction and amplification protocols to achieve optimal sensitivity and accuracy in ToBRFV detection.
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Figure 1. A-C) Symptoms of mosaic, leaf deformation, and leaf narrowing were evident in tomato saladette plants gathered from greenhouse settings. These plants tested positive for Tomato brown rugose fruit virus (ToBRFV); D-E) visual observations on inoculated Nicotiana leaves revealed the presence of localized chlorotic and necrotic lesions caused by ToBRFV infection. The virus-positive plants utilized for the study were sourced from Tecoman, Colima, Mexico.
Figure 2. The evaluation of total RNA extraction methods involved comparing their effectiveness and yield, as measured by absorbance readings on a Nanodrop 2000® spectrophotometer. Among the methods tested, including Trizol®, CTAB 2%, and CTAB 2%-Trizol®, the CTAB 2%-Trizol® protocol yielded the highest concentration of total RNA, while the RNA isolation Kit produced the lowest concentration. This data was recorded through absorbance measurements at wavelengths of 260/280 and 260/230. The Nanodrop 2000® was used to quantify the extracted RNA’s concentration and assess its quality by these absorbance ratios. The results indicated that the CTAB 2%-Trizol® protocol was particularly effective in extracting high-quality RNA from the plant samples, making it a suitable choice for subsequent molecular analyses.
Figure 3. Evaluation and sensitivity of PCR primers. 1.5% agarose gels electrophoretic analysis of RT-PCR and Nested RT-PCR products (Ling´s primers expected size 842 pb; Rodríguez-Mendoza´s primers expected size 475 bp and Dovas´s primers expected size 400 pb). (-): sterilized water instead RNA. 100 bp = 100bp DNA Ladder (Invitrogen®). 1Kb= 1000 bp DNA ladder (Promega®). 10-3 and 10-4 = 0.001 and 0.0001 ng μL-1.
Table 1. Primers tested in this study for ToBRFV detection in tomato, tomatillo, and eggplant
Table 2. Comparison of Primer References, Plant Sources, and RNA Detection Limits in source of infected plant material
by Carlos D. Ramos Villanueva ,Guadalupe Carrillo Benitez ,Erika J. Zamora Macorra* ,Eduardo Santiago Elena ,Samuel Ramírez Alarcón ,Jezrael Jimenez Vidals ,Ricardo Ricardo López
Accepted: 30/November/2023 – Published: 19/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-1
Abstract Background and objective: The Tomato brown rugose fruit virus (ToBRFV) is one of the main pathogens affecting tomato crops in Mexico. Despite efforts to prevent its spread, it is nearly impossible due to its low transmission percentage through seeds and its high susceptibility to being transmitted through cultural practices. Therefore, alternative management strategies are being sought. This research aimed to determine the effect of endophytic microorganisms applied to the soil on tomato plants infected with ToBRFV.
Materials and Methods. A tomato plant was used as an experimental unit, with 13 repetitions per treatment. The treatments on tomato plants infected with ToBRFV were Beauveria peruviencis, Trichoderma longibrachiatum, Pseudomonas sp. and water as a sick witness; a treatment of healthy plants treated with water was also included as an absolute control. The response variables were plant height, fresh weight of the aerial part and root and severity (two evaluations). Measurements were analyzed using Tukey-Kramer HSD tests for each pair. Results and conclusion: Significant differences were found Beauveria peruviencis, Trichoderma longibrachiatum, Pseudomonas sp. and water as a sick witness. The treatment that most favored the development of infected plants (79% taller and 15% heavier than infected mock) and reduced its severity was B. peruviensis, followed by Pseudomonas sp. On the other hand, the treatment that resulted in the least plant development (31% smaller than infected mock) and even increased the severity of the infection was T. longibrachiatum.
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Figure 1. A: Infected plants with Tomato brown rugose fruit virus (ToBRFV), treated with various microorganisms, and the diseased mock control. B: Healthy mock plants. C: Comparison among ToBRFV-infected plants treated with different microorganisms. D: Representative symptoms induced by ToBRFV, illustrating leaf mosaic at 20 days after inoculation (dai) and shoot deformation at 35 dai.
Figure 2. Mean of the response variables, obtained at the end of the experiment, for each treatment applied to ToBRFV- infected (diseased) and healthy tomato plants.
Figure 1. Comparison of mean values for response variables (height, severity, and weight of tomato plants) assessed under each treatment, accompanied by Tukey-Kramer HSD test-generated grouping letters.
by Erika Janet Zamora Macorra ,Norma Ávila Alistac* ,Erika Lagunes Fortiz ,Sergio de los Santos Villalobos
Accepted: 12/December/2023 – Published: 28/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-7
Abstract Viruses and viroids cause several diseases in tomato (Solanum lycopersicum) worldwide, generating important economic losses. About 312 viruses and seven viroids have been associated, of which more than 28 are present in Mexico. Therefore, the use of Plant Growth-Promoting Rhizobacteria (PGPR) can be an effective alternative for the management of viruses and viroids. The genera Pseudomonas, Bacillus, Azospirillum, Anabena and Stenotrophomonas have been implemented against main viruses reported in tomato: Cucumber mosaic virus (CMV), Tobacco mosaic virus (TMV), Tomato chlorotic spot virus (TCSV), Tomato mottle virus (ToMoV), Tomato spotted wilt virus (TSWV), Tomato yellow leaf curl virus (TYLCV), Potato virus Y (PVY), Groundnut bud necrosis virus (GBNV), with benefits in decreased incidence and severity up to 80 % and yield increase over 40 %. In Mexico, only Bacillus has been used. The use of PGPR is a strategy that could mitigate the impact of viral and viroid diseases and can be integrated into integrated management.
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Figure 1. States of the Mexican Republic where viruses and viroids were detected in tomato (See Table 1)
Figure 2. Main forms of transmission of viruses and viroids in tomato. A) Transmission by seed; B) Mechanical transmission, due to the use of work tools, manipulation of plants; C) Transmission by insect vectors.
Figure 3. Symptoms associated with viruses and viroids in tomatoes. A and B) Mosaic, leaf reduction, and mild to severe leaf distortion associated with Tomato brown rugose fruit virus; C and D) Stunting, fruit deformation, and purple discoloration in leaves caused by Mexican papita viroid; E) Yellow mosaic symptom associated with Pepino mosaic virus; F) Symptoms of stunting, deformation, and severe mosaic associated with Begomovirus; G and H) Symptoms of concentric rings and slight fruit deformation associated with Tomato spotted wilt virus; I) Mosaic in leaves caused by Tobacco mosaic virus
Figure 4. Forms of application and mechanisms of action of Plant Growth-Promoting Rhizobacteria (PGPR) used to protect tomatoes from viral infections.
Table 1. Main viruses reported in tomato (Solanum lycopersicum) in Mexico and the world
Table 2. Viroids that affect tomato (Solanum lycopersicum) in the world
Table 3. Plant growth-promoting rhizobacteria species used for virus management in tomato.
Weeds and ruderal plants as potential sources of inoculum for vegetable diseases in northern Sinaloa
by Rubén Félix Gastélum ,Gabriel Herrera Rodríguez ,Karla Yeriana Leyva Madrigal ,Guadalupe Arlene Mora Romero
Accepted: 15/December/2023 – Published: 28/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2023-4
Abstract Weeds and ruderal plants of the families Cucurbitaceae and Solanaceae are addressed as potential sources of inoculum for the development of viral diseases such as Tomato apex necrosis virus (ToANV), zucchini (Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Papaya ring spot virus (PRSV-W) and Cucumber mosaic virus (CMV). Reference is made to weeds and ruderal plants as potential sources of inoculum, including wild sunflower for powdery mildew (Golovinomyces spadiceus), wild tobacco for foliar blight (Alternaria spp.), black nightshade for leaf spot (Curvularia moehlemvekiae), Johnson grass for foliar blight (Alternaria sp.), and wild castor bean for foliar blight (Alternaria ricini) and wild melon for downy mildew (Pseudoperonospora cubensis). Future lines of multidisciplinary research focusing on the determination of pathogenicity in cultivated plants of viruses and fungi associated with wild plants and vice versa are proposed; the spatial-temporal distribution of wild plants that may serve as sources of inoculum, as well as the of potential insect vectors of viral diseases, should also be studied. The implementation of modern molecular techniques, such as High Throughput Sequencing, for the detection of phytopathogens is important. All this will contribute to the implementation of environmentally friendly strategies for disease control in agricultural crops in Sinaloa, for the benefit of the vegetable growers
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Figure 1. Symptoms induced by Tomato apex necrosis virus (ToANV). A) Necrosis in young growth of tomato; B) Necrosis in tomato fruit; C) interveinal chlorosis in leaves of husk tomato; D) Yellowing in wild husk tomato (Physallis sp.); E) Slight yellowing and deformation of initial leaves in black nightshade (Solanum nigrum); F) Initial symptoms of interveinal chlorosis; G) Intense chlorosis and vein greening of wild tobacco (Nicotiana glauca) leaves; H) General yellowing in black nightshade (Solanum asureum).
Figure 2. Symptoms induced by the virus Zucchini yellows mosaic virus (ZYMV). A) Yellowing in Zucchini squash var. Grey leaf; B) Symptoms of deformation of the fruit of the same host caused by the same virus.
Figure 3. Symptoms induced by the virus Zucchini yellows mosaic virus (ZYMV). A) Yellowing in Zucchini squash var. Grey leaf; B) Symptoms of deformation of the fruit of the same host caused by the same virus.
Table 1. Viruses causing diseases in cucurbits and tomato in Sinaloa and other parts of the world
Cellulase and chitinase production by Fusarium oxysporum f.sp. cubense race 1 in submerged culture
by Dulce Jazmín Hernández Melchor ,Ronald Ferrera Cerrato ,Clemente de Jesús García Ávila ,Alejandro Alarcón*
Accepted: 21/December/2023 – Published: 29/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2307-2
Abstract Background/Objective. Fusarium has the capability to produce hydrolytic enzymes that can be used in the food and alcohol industries to break down natural organic compounds. This work studied the ability of Fusarium oxysporum f. sp. cubense race 1 (FocR1) to produce cellulases and chitinases enzymes in submerged culture using different carbon sources.
Materials and Methods. Five strains of FocR1 (CNRF-MIC17188, CNRF-MIC17189, CNRF-MIC17190, CNRF-MIC17191, and CNRF-MIC17192) were used in submerged culture for the degradation of three substrates [filter paper, newspaper, and chitin (Sigma®)], from where the radial growth rate (RGr) and the quantitative analysis of enzyme activities (FPase, CMCase and chitinase) were evaluated.
Results. The RGr of the five FocR1 strains oscillated in a range of 0.043 to 0.051 cm h-1. At 7 and 14 days, the five FocR1 strains produced cellulases and chitinases using the three substrates. Based on the statistical analysis, the strains CNRF-MIC17191 and CNRF-MIC17192 showed best results about enzymatic activities.
Conclusion. The five strains of FocR1 can be exploited as a commercial source of cellulases and chitinases, as well as potential candidates for bioconverting complex C-sources for further utilization in industrial processes
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Figure 1. Radial growth rate (RGr) of Fusarium oxysporum f.sp. cubense Race 1 (FocR1) strains in PDA medium, at 192 h. Different letters on bars are significantly different (Tukey; p≤0.05). Means ± standard error, n=3.
Figure 2. Quantitative enzymatic activity of five strains of Fusarium oxysporum f.sp. cubense Race 1 (FocR1) using newspaper as substrate, at 7 and 14 days. A) Cellulase activity (FPase). B) Carboxymethyl cellulase (CMCase). C) Chitinase activity. Different letters over the bars in the three graphs are significantly different (Tukey; p≤0.05). Means ± standard error, n=3.
Figure 3. Quantitative enzymatic activity of five strains of Fusarium oxysporum f.sp. cubense Race 1 (FocR1) using filter paper as substrate, at 7 and 14 days. A) Cellulase activity (FPase). B) Carboxymethyl cellulase (CMCase). C) Chitinase activity. Different letters over the bars in the three graphs are significantly different (Tukey; p≤0.05). Means ± standard error, n=3.
Figure 4. Quantitative enzymatic activity of five strains of Fusarium oxysporum f.sp. cubense Race 1 (FocR1) using chitin as substrate, at 7 and 14 days. A) Cellulase activity (FPase). B) Carboxymethyl cellulase (CMCase). C) Chitinase activity. Different letters over the bars in the three graphs are significantly different (Tukey; p≤0.05). Means ± standard error, n=3.
Diagrammatic scale to quantify the severity of Ascochyta blight in broad bean crops
by Ernesto Alonso López Reyes ,Álvaro Castañeda Vildózola* ,Jesús Ricardo Sánchez Pale ,Alejandra Contreras Rendón ,Juyma Mayvé Fragoso Benhumea ,Rómulo García Velasco
Accepted: 10/December/2023 – Published: 26/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2209-4
Abstract Background/Objective. The objective of this study was to design and validate a diagrammatic severity scale of brown spot on broad bean.
Materials and Methods. We collected 120 leaflets with different level of brown spot damage from commercial crops in the Toluca Valley, which were visually selected based on the expressed symptomology. Sixty leaflets were scanned for evaluation with the software APS PRESS ©Assess 2.0 to determine the real severity value for each leaflet.
Results. The damage values allowed us to generate a diagrammatic scale consisting of six different classes: 0(0.0), 1(0.1-6.0), 2(6.1-10.0), 3(10.1-15.0), 4(15.1-40.0), 5(> 40.1-100). The leaflets were visually examined by evaluators who had no prior experience. The results from each evaluator were analyzed with a simple linear regression, obtaining r2 values from 0.0042 to 0.8748, β0 de 0.51 a 9.11, y β1 de 0.132 a 0.925. Using a scale, r2 values were obtained 0.9143 to 0.985, β0 de 0.001 a 0.911 y β1<0.001.
Conclusion. The generated diagrammatic severity scale was validated and reproducible, showing high reliability.
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Figure 1. Diagrammatic scale of brown spot severity (Ascochyta fabae) in broad bean. zLower limit-average-upper limit.
Figure 2. Distribution of residuals (estimated severity-real severity) of the brown spot evaluations (Ascochyta fabae) in broad bean leaflets. A) Scaled evaluation. B) Unscaled evaluation.
Table 1. Values of the Intercept (β0), slope of the line (β1), coefficient of determination (r²) and margin of error (1-r²) of the simple linear regression equation in visual estimations of the severity in of brown spot in broad bean (Ascochyta fabae), with 20 unscaled evaluators and 10 scaled evaluators
Biostimulant effect of native Trichoderma strains on the germination of four varieties of basil
by Juanita Guadalupe Hollman Aragón ,Mirella Romero Bastidas* ,Pablo Misael Arce Amezquita ,Alejandro Palacios Espinosa
Accepted: 09/December/2023 – Published: 19/December/2023 – DOI: https://doi.org/10.18781/R.MEX.FIT.2303-1
Abstract Objetive/antecedents. Trichoderma is an efficient tool as biostimulant in basil crop. However, only few species have been studied in specific cultivars. Therefore, the objective of this research was to evaluate the biostimulant efficacy of native Trichoderma strains on the germination and growth of four varieties of basil.
Materials and Methods. Seven strains of Trichoderma (T. asperellum, atroviride, viride, longibrachiatum, harzianum, koningii and Trichoderma sp.), a commercial Trichoderma (T. harzianum), synthetic fertilizer (T17) and the control were used in the study. 30 seeds of the Purple Ruffles, Lemon, Siam Queen and Nufar varieties were treated with a spore suspension of each Trichoderma. 48 h later, the seeds were sown and incubated at 28 °C with a 12 h light/dark photoperiod. The variables evaluated were; Rate and percentage of germination, biomass and length of seedlings.
Results. T. atroviride presented the greatest biostimulant effect on germination (95%). While T. asperellum registered an increased efficiency in biomass (≥ 0.120 g) and length (≥ 1.0 cm) of the plant in the four varieties. The action of commercial T. was lower in all cases.
Conclusion. This study demonstrated that the native strains of Trichoderma have a biostimulant effect on plants and are more effective than commercial species.
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Figure 1. Biostimulating action of native Trichodermas in the percentage of germinated seeds of four varieties of basil
Figure 2. Main Trichoderma treatments with the highest positive (1st. and 2nd. photo from the left) or negative response (3rd. photo on the right) in the growth of four basil cultivars
Table 1. Morphometric parameters of basil Var. Purple Ruffles seedlings against the effect of different Trichoderma isolates
Table 2. Morphometric parameters of basil Var. Lemon against the effect of different Trichoderma isolates.
Table 3. Morphometric parameters of basil Var. Siam Queen against the effect of different Trichoderma isolates
Table 4. Morphometric parameters of basil Var. Nufar against the effect of different Trichoderma isolates