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Búsquedas previas al 2023, Núm. 3. En la sección Volúmenes 30 - 41 (2012 - 2023).
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byGermán Ramírez Jiménez, Omar G. Alvarado Gómez, Magdiel Torres de la Cruz*, Miguel Ángel Mayo Hernández, Ángel F. Huamán Pilco, Jorge R. Díaz Valderrama
Received: 07/June/2024 – Published: 21/February/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2406-2
Abstract Background/Objective. Garlic (Allium sativum) is a crop of economic relevance in Mexico. Nuevo León stands out in production; however, in the municipality of Aramberri, post-harvest losses have been reported due to diseases of unknown etiology. The objective of this work was to identify the fungi associated with the postharvest deterioration of A. sativum bulbs in Aramberri, Nuevo León, Mexico and to evaluate their in vitro sensitivity to fungicides.
Materials and Methods. From bulbs with evidence of deterioration and necrosis, fungi were isolated in PDA medium. Four isolates were identified by morphological analysis and one isolate from each morphological species was identified by molecular analysis. The pathogenicity of the four isolates on symptom-free bulbil was evaluated. In addition, in vitro susceptibility tests of the isolates to protective and systemic fungicides were performed. Fungicides were evaluated at three concentrations and mycelial growth reduction (MGR) and conidial germination inhibition (CGI) was estimated.
Results. The fungi Alternaria embellisia and Penicillium allii were identified in association with A. sativum bulbs with postharvest deterioration. P. allii showed the ability to develop internal infections from wounds; A. embellisia only showed growth on wounds. There were significant differences (p <0.0001) in the effectiveness of fungicides on the two species. Propiconazole and copper hydroxide inhibited 100% MGR and CGI in both fungi, at all doses evaluated.
Conclusion. P. allii is first reported as a causative agent of green garlic rot in Mexico. This study will serve as a basis for choosing control strategies and will contribute significantly to reducing economic losses in garlic production in this region.
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Table 1. Systemic and protectant fungicides evaluated against Alternaria embellisia and Penicillium allii.
Table 2. Effectiveness of systemic and protectant fungicides on mycelial growth and spore germination of Alternaria embellisia and Penicillium allii in vitro.
Figure 1. A. Allium sativum bulbs of the “Don Fermín“ variety showing postharvest deterioration. B. A. sativum bulbils with cankers and green mold.
Figure 2. Alternaria embellisia (syn. Embellisia allii), isolates AL1D2B and AL1D3B. A. Seven-day-old colony growing on PDA medium at 25 °C. B, C. Simple conidiophore and solitary conidium. D, E. Branched conidiophore. F. Septate conidia. G, H. Chlamydospores.
Figure 3. Penicillium allii, isolates AL1D4B and AL1D5B. A. Seven-day-old colony growing on PDA medium at 25 °C. B. Conidiophore showing stipe and metula with rough walls. C. Conidiophore. D. Conidiophore with phialides and conidiation forming chains. E. Conidia. F, G. Terminal and intercalary chlamydospores.
Figure 4. A. Maximum likelihood phylogenetic tree constructed from partial sequences of the internal transcribed spacer 1 and 2 regions within the 5.8S rDNA subunit for the isolation of Alternaria embellisia (GenBank accession number: PP869831). B. Maximum likelihood phylogenetic tree constructed from partial sequences of the β-tubulin gene for the isolation of Penicillium allii (GenBank accession number: PP920512); both obtained from garlic bulb samples with postharvest rot in Aramberri, Nuevo León. Data for other Alternaria strains and species were obtained from Pryor and Bigelow (2003), while data for other Penicillium strains and species were sourced from Samson et al. (2004). The numbers next to the nodes indicate bootstrap support values in percentage.
Figure 5. Pathogenicity test of (A) Penicillium allii (AL1D4B) and (B) Alternaria embellisia (AL1D2B) on Allium sativum bulbils, 14 days after inoculation. (C) Control. Each bulbil in the same column represents repetitions of the isolate.
byOscar Guillermo Rebolledo Prudencio, Wilberth Chan Cupul*, Guadalupe Moreno Zúñiga, Carlos Adrián Cruz Jiménez, Juan Carlos Sánchez Rangel
Received: 15/November/2024 – Published: 21/February/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2024-09
Abstract Background/objective. In Tecoman, Colima, Mexico, a leaf spot (LS) disease was detected with an incidence of 92.0% in Cocos nucifera hybrid Brazilian Green Dwarf (BGD). The objective was to characterize morphologically, molecularly and biochemically the fungus associated with LS in BGD coconut palm and evaluate its susceptibility to commercial biological fungicides.
Materials and methods. The isolate was characterized morphologically and molecularly. Their growth, sporulation and laccase production were evaluated using different culture media. The in vitro mycelial inhibition and mean lethal doses (LD50) of commercial biological fungicides based on antagonistic fungi (Trichoderma harzianum and T. viride), bacteria (Bacillus subtilis and B. amyloliquefaciens) and actinobacteria (Streptomyces lydicus and S. jofer) were determined.
Results. Bipolaris oryzae was the associated agent of LS, it produces 25.54 and 22.17 U mg of protein-1 of laccase activity in the Sivakumar and wheat bran (WB) media. The WB medium allowed the greatest sporulation. Trichoderma harzianum inhibited B. oryzae at 100% in the four evaluated doses. B. subtilis and B. amyloliquefaciens inhibited B. oryzae at 100% at the highest tested doses (20 mL L-1).
Conclusion. Bipolaris oryzae is the associated agent of LS, it produced the highest laccase activity in Sivakumar and WB culture media. The highest sporulation and daily growth rate were in WB. T. harzianum stood out over T. viride by inhibiting B. oryzae growth by 100%. B. subtilis, S. lydicus and B. amyloliquefaciens were more effective against B. oryzae in vitro compared to S. jofer.
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Table 1. Sequences used to generate the phylogenetic tree for Bipolaris oryzae, an agent associated to the coconut tree leaf spot.
Table 2. Laccase activity, daily growth rate (DGR) and sporulation of Bipolaris oryzae in semi-solid media.
Table 3. Inhibition of the mycelial growth (%MGI) of Bipolaris oryzae by different doses of commercial biological fungicides.
Table 4. Ninety lethal dose (LD90) of six commercial biological fungicides on Bipolaris oryzae.
Figure 1. Leaves with symptoms of leaf spot in hybrid coconut tree “Brazilian Green Dwarf”. A) Brown oval spots and yellow halo, B) palm leaves with multiple oval spots and C) view of the nursery with plants with leaf spot.
Figure 2. Cultural and morphological characteristics of Bipolaris oryzae. A and B) Conidiophores; C to F) conidiospores; G) cluster of conidiophores; H) septated hyphae; I) young mycelium, aged 5 days in medium; J) mature mycelium after 20-day growth in PDA medium.
Figure 3. Phylogenetic analysis based on the maximum likelihood method using the 2 parameter Kimura method (G+I). Tree created with the highest probability logarithm (-5759.36) of the sequence of rDNA 28S of the Bipolaris strains, similar to those of the agent associated to LS in the BGD coconut tree (Bipolaris oryzae ACMFCnhEVB_1) using MEGA11. This tree was rooted using Fusarium oxysporum and was used as an external group.
Figure 4. Growth of Bipolaris oryzae five days after inoculation in PDA modified with different doses of commercial biological fungicides.
Figure 5. Linear regression between the inhibition (%) in the growth of Bipolaris oryzae and the doses of each commercial biological fungicide used.
byMaría del Sol Cuellar Espejel, Evangelina Esmeralda Quiñones Aguilar, Gabriel Rincón Enríquez*, Rodolfo Hernández Gutiérrez, Juan Carlos Mateos Díaz, Sergio David Valerio Landa
Received: 15/November/2024 – Published: 13/February/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2024-25
Abstract Background/Objective. Diseases such as bacterial spot in tomato (Solanum lycopersicum) and bacterial spot in chili pepper (Capsicum annuum) cause significant global economic losses. A sustainable alternative for their control is the use of protein inducers (Harpin proteins = Hrp) that activate plant defense responses by being recognized by the plant immune system, inducing defense mechanisms against pathogens. The objective of this research was to evaluate the biological effectiveness and optimal application dose of the biological inducer BioFensa (based on Hrp proteins), produced in a pilot plant, to control these diseases.
Materials and Methods. Three greenhouse experiments were conducted to evaluate the biological effectiveness of BioFensa (1 μg mL⁻¹). The protein inducer was tested for controlling bacterial spot (X. euvesicatoria strain BV865 [1] and BV801 [2]), as well as bacterial speck (P. syringae pv. tomato, strain DC3000 [3]). Each experiment included 5 treatments and 11 replicates. Additionally, an experiment was conducted to determine the optimal dose of BioFensa (0.01, 0.1, and 1.0 μg mL⁻¹) against X. euvesicatoria strain BV801, with 7 treatments and 8 replicates [4]. In the four experiments in total, plants were sprayed with BioFensa (3 mL per plant) 24 hours before infection, and symptoms were evaluated after 30 days by counting spots on the foliar tissue.
Results. BioFensa was effective in significantly reducing damage in chili and tomato plants (LSD, p≤0.05). At a high concentration (1 μg mL⁻¹), it prevented the appearance of spots on tomato plants by 53%, while for chili plants against strain BV865, it prevented spots by 60%. On the other hand, for chili plants against strain BV801, at low concentrations (0.01 and 0.1 μg mL⁻¹), symptoms were significantly reduced by 38-41%, whereas at a higher concentration (1 μg mL⁻¹), this effect was not maintained, suggesting a limit in the perception of inducers by the plants.
Conclusion. The results suggest that BioFensa has the potential to be an effective alternative to control diseases in horticultural crops such as tomatoes and chili peppers.
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Table 1. Composition of the treatments of Experiment 4 to determine the effect of different doses of the protein inducers under greenhouse conditions for chili pepper plants.
Figure 1. Biological effectiveness of different biological treatments for the control of P. syringae pv. tomato, strain DC3000 (bacterial speck) in tomato plants under greenhouse conditions, depending on the amount of necrotic, chlorotic and total spots per plant. PS=Healthy plant; PE=Diseased plant; AG=Actigard® (0.003 g mL−1); MG= Messenger Gold® (0.003 g mL−1); BF= BioFensa (1 μg mL−1). Different letters in each response variable indicate significant differences according to the LSD test (p≤0.05). Bars in the rectangle indicate ± the standard error.
Figure 2. Biological effectiveness of different biological treatments for the control of X. euvesicatoria, strain BV865 in ancho chili pepper plants, San Luis variety, under greenhouse conditions, depending on the amount of necrotic, chlorotic and total spots per plant. PS=Healthy plant; PE=Diseased plant; AG=Actigard® (0.003 g mL−1); MG= Messenger Gold® (0.003 g mL−1); BF= BioFensa (1 μg mL−1). Different letters in each response variable indicate significant differences according to the LSD test (p≤0.05). Bars in the rectangle indicate ± the standard error.
Figure 3. Biological effectiveness of different biological treatments for the control of X. euvesicatoria, BV801, in ancho chili peppers San Luis variety under greenhouse conditions, according to the number of necrotic, chlorotic and total spots per plant. PS=Healthy plant; PE=Diseased plant; AG=Actigard® (0.003 g mL−1); MG= Messenger Gold® (0.003 g mL−1); BF= BioFensa (1 μg mL−1). Different letters in each response variable indicate significant differences according to the LSD test (p≤0.05). Bars in the rectangle indicate ± the standard error.
Figure 4. Effect of different doses of BioFensa (0.01, 0.1 and 1 μg mL−1) on the control of X. euvesicatoria, strain BV801 on ancho chili plants, San Luis variety, under greenhouse conditions. PS=Healthy plant; PE=Diseased plant. Different letters indicate, within each response variable, significant differences according to the LSD test (p≤0.05). Bars in the rectangle indicate ± the standard error.
byWilberth Chan Cupul*, Osvaldo Villegas Guerrero, Juan C. Sánchez Rangel, Gilberto Manzo Sánchez, Marco T. Buenrostro Nava
Received: 15/November/2024 – Published: 13/February/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2024-05
Abstract Background/Objective. Black Sigatoka (BS) is one of the main phytopathologies that reduces banana production in Mexico. Developing biological products based on antagonists is a predominant study activity. The production of conidiospores of Trichoderma spp. strains was evaluated in solid state fermentation using whole rice grains and cracked corn, and the effect of foliar applications of conidiospores against the BS epidemiology in banana cv. Great dwarf.
Materials and methods. In solid state fermentation, the yield of four strains of Trichoderma spp. (T-82, T-85, T-94 and T-99) in whole rice (WR) and cracked corn (CC) was evaluated, an A×B factorial design was used (A=strains and B=substrate). The two strains with the best yield (T-99 and T-85) and a Streptomyces spp. based product was applied in the field to evaluate the epidemiology of BS through the severity, weighted average of infection (WAI) and area under the disease progress curve (AUDPC), through a randomized block design.
Results. CC increased the yield of Trichoderma spp. in 71%, strains T-94 (1.41×108 conidiospores g-1) and T-85 (1.20×108 conidiospores g-1) achieved the highest yields. The T-85 strain reduced the severity, WAI and AUDPC of BS compared to applications of the chemical control “Mancozeb”.
Conclusion. CC was the best substrate to obtain greater yield in Trichoderma spp. T-94 and T-85. The weekly application of conidiosporas of Trichoderma T-85 reduces the severity, WAI and AUDPC of the SN in banana cv. Great dwarf.
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Table 1. Yield of Trichoderma spp. strains on solid substrates.
Table 2. Severity of black Sigatoka in “Gran Enano” banana through applications of Trichoderma spp.
Table 3. Weighted infection average (WIA) of black Sigatoka in “Gran Enano” banana through applications of Trichoderma spp.
Figure 1. Total area under the disease progress curve (AUDPC) of black Sigatoka in “Gran Enano” banana through applications of Trichoderma spp.
Figure 2. Behavior of the area under the disease progress curve (AUDPC) of black Sigatoka in Gran Enano banana through applications of Trichoderma spp.
byJeny Michua Cedillo, Gustavo Mora Aguilera*, Gerardo Acevedo Sánchez
Received: 30/July/2024 – Published: 31/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2406-7
Abstract Background/Objective. Nectriaceae members increased regional occurrence in Michoacán since 2019. However, root species identity, geographic distribution, and association to other families are unknown. The objective was to characterize biological and molecularly species of Nectria associated with Persea americana.
Materials and Methods. Seventy samples of wilt trees from 13 municipalities in Michoacán were processed. Thirty isolates selected based on epidemiological criteria were cultured in malt-agar, PDA, and oat-agar extracts to determine cultural and morphological characterization. Five morphotypes of Nectria with varying radial growth and brown coloration were obtained. From mycelial DNA, TEF 1-a and RPB2 genes were amplified, sequences were cleaned and aligned with SeqAssem and MAFFT, respectively. Bayesian inference and maximum parsimony phylogenetic algorithms were performed using PAUP 4.0 and MrBayes 3.2 complemented with 66 and 65 sequences from GenBank for TEF 1-a and RPB2, respectively. S. chartarum was used as the external species and four other Hypocreales.
Results. Bayesian inference revealed greater phylogenetic consistency. Three genera and three species were identified with TEF 1-a (>94 % homology) and three genera and five species with RPB2 (>97 % homology) belonging to Ilyonectria (56 %), Dactylonectria (33 %), Mariannaea (6 %), and Thelonectria (3 %). Associations of Nectria were observed mainly to Armillaria (97.1 %), Fusarium (92.9 %), Paecilomyces (56.4 %), and Morthierella (47.3 %).
Conclusion. A decline syndrome in avocado trees associated with a fungal complex characterized by descending defoliation, wilt, reduced fruit size, and root necrosis is postulated. This is the first report of Nectria associated fungi in avocado trees in Mexico.
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Figure 1. A. Healthy tree and longitudinal and transversal section of 1.5 cm diameter root and association of Ilyonectria liriodendri; B. Apical defoliation, longitudinal and transverse root section with restricted necrosis associated to I. liriodendri; C. Fruit size reduction, longitudinal and transverse root cutting showing invasive necrosis associated to I. liriodendri; D. Defoliation and small leaves associated with Armillaria + I. liriodendri and root with medullary necrosis; E. Moderate wilt associated with Phytophthora + I. liriodendri and longitudinal root cutting showing restricted necrosis; F. Yellow canopy, small leaves and canopy reduction associated to Fusarium + Dactylonectria macrodidyma and root with medullary invasive necrosis. G. Progressive wilt and root necrosis, and invasive mycelia in root tissue associated with Armillaria sp.; H. Wilt, yellowing of canopy and root with subcortical necrosis associated with Phytophthora cinnamomi; I. Total wilt, necrotic foliage adhering to branches, root with lines of necrosis in vascular tissue associated to Verticillium sp.
Figure 2. Nominal scale of six classes of vigor and damage in secondary roots of avocado trees associated with four genera and five species of Nectria. 0. Healthy tree with 100% vigor and root without lesions; 1. Apical defoliation in upper branches, root with reddish lesions <1 cm in central tissue (80 % canopy tree); 2. Progressive apical defoliation in upper branches, yellowing in lower stratum of leaves, root with reddish lines in medullary parenchyma (75 %); 3. Defoliation, wilt, and root with invasive necrosis in subcortical and medullary tissue (50 %); 4. Partial defoliation, small leaves and root with necrosis in xylem and primary and secondary phloem (35 %); 5. Defoliated tree and root with invasive necrosis (15 %).
Figure 3. Cultural morphotypes of avocado tree’s root isolates with Nectria-associated symptoms molecularly identified with 97 and 64% homologies for RPB2 y TEF 1-α genes. A-D. Dactylonectria macrodydima; F-I. Dactylonectria novozelandica; J-M. Ilyonectria liriodendri; N-Q. Mariannaea samuelsii; R-T. Thelonectria lucida.
Figure 4. Cultural morphotypes in EMA at 2 % (A, B) and PDA (C, D) isolated from symptomatic avocado tree roots associated with Nectria and other organisms and identified morphologically. A. Armillaria sp; B. Armillaria gallica; C. Phytophthora cinnamomi; D. Fusarium sp.
Figure 5. Phylogenetic tree obtained by Bayesian inference analysis of sequences associated with RPB2 gene of Nectria isolates collected in commercial avocado trees. Nectria species from this study are indicated with the MICH prefix. The tree had S. chartarum (KM231994.1) as external reference. The scale-bar represents the expected number of nucleotide changes per site.
Figure 6. Phylogenetic tree obtained by Bayesian inference analysis of sequences associated with TEF 1-α gene of Nectria isolates collected in commercial avocado trees. Nectria species from this study are indicated with the MICH prefix. The tree had S. chartarum (KM231994.1) as external reference. The scale-bar represents the expected number of nucleotide changes per site.
Figure 7. Distribution and regional prevalence of soil and root communities of organisms putatively associated with avocado tree decline and wilt syndrome in 13 municipalities of Michoacán. A. Phylogeographic distribution of four Nectria genera. B. Phylogeographic distribution for six Nectria species. Armillaria spp. and Fusarium spp. are included as species of high regional prevalence (comparative purposes). Green-Yellow-Brown shows the epidemic intensity (low, moderate, and high) assessed by severity scale per tree sampled
Figure 8. Associativity plots of organisms isolated from avocado tree roots with symptoms of decline syndrome. A. Pearson's correlation (r) showing association between Nectria and other soil-root organisms; y B. Cross-correlation in pairs and ordered by level of associativity for the top 25 significant correlations.
Table 1. Characteristics of orchards from Nectria isolates selected for DNA extraction and amplification.
Table 2. Physicochemical characteristics of orchards sampled for Nectria isolates in avocado trees.
byGabriela Olivares Rodriguez, Juan Gabriel Angeles Núñez, Francisco Mondragón Rojas, Patricia Rivas Valencia, José Luis Zárate Castrejón, Luis Antonio Mariscal Amaro, Luis Febronio Díaz Espino, Talina Olivia Martínez Martínez*
Received: 10/July/2024 – Published: 31/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2024-28
Abstract Background/Objective. The fungi Neopestalotiopsis sp. is an emerging pathogen that can cause losses of more than 70 % of production in strawberry crops. Due to this situation, is necessary to evaluate and implement control methods with low ecological impact. The objective of this work was evaluated the inhibitory growth of Neopestalotiopsis sp. using antagonist strains of Trichoderma sp. and fungicides used locally in the Bajio of Guanajuato, México.
Materials and Methods. The pathogen was isolated in strawberry symptomatic plants. The morphological and pathogenicity characterization of the isolate was carried out. The Trichoderma strains were obtained from the biological collection of the National Forestry, Agricultural and Livestock Institute (INIFAP), Bajio Experimental Field (CEBAJ), and were confront in dual cultures with the pathogen, the percentage of radial growth inhibition (PRGI) was calculated at 120 h. In addition, five commercial fungicides were added to the growth medium and was calculated the growth diameter of the fungus.
Results. The PRGI by Trichoderma were observed in a range of 63 to 70 %. The mechanisms of parasitism for Trichoderma were curling, adhesion and lysis to the pathogen hypha. The T1 strain was the greatest potential for controlling the pathogen, followed by T5 and T7. Three fungicides, Tecobenazole (100 mL 100 L-1), Cinnamon and Neem extract (500 mL 100 L-1), and Peracetic Acid (25 mL 100 L-1) had 100 % inhibited of fungal growth.
Conclusion. These results contribute to the knowledge on the control of Neopestalotiopsis sp. with the application of Trichoderma and the authorized products in Mexico
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Figure 1. Symptoms in strawberry plants infected by Neopestaloptiosis sp. A) Stunting of plants, B) Blight in leaves, C and D) Deformation in mature and immature fruits.
Figure 2. Growth of Neopestalotiopsis sp. in a PDA medium after two weeks of inoculation. A) Development of colonies in a culture medium with black acervuli, B and C) Fungal conidia.
Figure 3. Symptoms on strawberry plants caused by Neopestalotiopsis sp. A) Blight on leaves, B) Necrosis on the stem and C) Necrosis in neck and leaves.
Figure 4. Percentage of inhibition of root growth for Neopestalotiopsis sp. obtained from the confrontation with Trichoderma strains (p≤0.05).
Figure 5. Confrontations of Trichoderma strains against Neopestalotiopsis sp. where T = Trichoderma and P = pathogen. The
number found on the top right corner corresponds to the identification of the Trichoderma strain. T1, T5 and T7 are
observed to maintain a level II antagonism, while T4, T8 and T10 maintain a level III.
number found on the top right corner corresponds to the identification of the Trichoderma strain. T1, T5 and T7 are
observed to maintain a level II antagonism, while T4, T8 and T10 maintain a level III.
Figure 6. Mechanisms of parasitism in Trichoderma sp against Neopestaloptiopsis sp. A) Curling, B) Formation of hooks and C) Adhesion and lysis.
Figure 7. Growth of Neopestalotiopsis sp in a PDA medium with commercial fungicides. Test: control with no product; A-C: Captan 200, 300 and 400 g 100 L-1; D-F: Tebuconazole 100, 250 and 375 mL 100 L-1; G-I: Carbendazim 400, 500 and 600 mL 100 L-1; J-L: Extract of Cinnamon and Neem 500, 1000 and 1500 mL 100 L-1; M-O: Peracetic Acid 25, 50 and 75 mL 100 L-1; P-R: Citrus-based organic fungicide 500, 750 and 1000 mL 100 L 1 . 400 g and 600 mL 100 L-1 (p≤0.05).
Table 1. Identification data, isolation substrate and origin of the Trichoderma sp. strains used in the biological control of Neopestalotiopsis sp.
Table 2. Fungicides evaluated in Neopestalotiopsis sp. growth inhibition.
Table 3. Level of antagonism according to Bell et al. (1982) and mycoparasitim mechanisms.
byAna Patricia Ibarra Valenzuela, Rosalba Troncoso Rojas, Alma Rosa Islas Rubio, Elizabeth Peralta, Herlinda Soto Valdez*, Hayati Samsudin
Received: 09/April/2024 – Published: 31/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2404-4
Abstract Objective/Background. Corn tortillas are a staple food in México that have a shelf life of 1-2 days at 25 °C due to fungal growth. A natural alternative for controlling fungal growth is clove essential oil (AEC) and its major components: eugenol (E), isoeugenol (I), and eugenyl acetate (AE). Objective: to evaluate the antifungal effect of AEC on the identified fungi present in corn tortillas.
Materials and Methods. One kg samples of corn tortillas were obtained from the capitals of five states of Mexico (Sonora, Nuevo León, Michoacán, Oaxaca y Yucatán). Fungi were identified by their morphology and molecular biology. Moreover, the minimum inhibitory concentration (MIC) against AEC was determined. The effect of E, I, and AE on Aspergillus niger was evaluated with the Gompertz model.
Results. Two fungi were isolated from corn tortillas purchased in Nuevo León, Sonora, Yucatán, and Michoacán, and one fungus from those purchased in Oaxaca. The following fungi were identified by molecular biology in corn tortillas: Aspergillus longivesica and Curvularia spicifera from Nuevo León; Aspergillus niger and Penicillium brevicompactum from Sonora; Aspergillus sp. from Oaxaca; Mucor sp. and Aspergillus flavus from Yucatán; Penicillium herquei and Curvularia racemosus from Michoacán. The MICs were 200, 400, 800, 400, 800, 400, 800, 800, and 400 µg mL-1, respectively. AEC, E, and I at a concentration of 800 µg mL-1 delayed the growth exponential phase of Aspergillus niger, while AE did not show any effect.
Conclusion. AEC could be a natural alternative for prolonging the corn tortillas′ shelf life.
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Figure 1. Fungal structure by optic microscopy (40X), isolated from corn tortillas from Morelia, Mich (A: Penicillium sp. and F: Mucor sp.), Monterrey, N.L. (B: Aspergillus sp. and G: Curvularia sp.), Oaxaca, Oax (C: Aspergillus sp.), Hermosillo, Son (D: Penicillium sp. and H: Aspergillus sp.) and Mérida, Yuc (E: Aspergillus sp. and I: Mucor sp.).
Figure 2. Growth of fungi in PDA isolated from corn tortillas from Morelia, Mich (A, Penicillium sp. and F, Mucor sp.), Monterrey, N.L. (B, Aspergillus sp. and G, Curvularia sp.), Oaxaca, Oax (C, Aspergillus sp.), Hermosillo, Son (D, Penicillium sp. and H, Aspergillus sp.) and Mérida, Yuc (E, Aspergillus sp. and I, Mucor sp.).
Figure 3. Antifungal effect of AEC, E and I on the growth of Aspergillus niger on PDA 96 h after de incubation at 25 ± 1 °C.
Figure 4. Kinetics of mycelial growth of Aspergillus niger on PDA for 96 h of incubation at 25 ± 1 °C. yVal= y values; Fit 1=curve with adjusted data.
Table 1. Minimum inhibiting concentration (MIC) of clove essential oil on fungi (250 conidia) isolated from corn tortillas.
Table 2. Kinetic parameters of the effect of the clove essential oil (AEC), eugenol (E) and isoeugenol (I) on the mycelial growth of Aspergillus niger incubated at 25 ± 1 °C for 96 h, obtained with Excel DMFit 3.5.
byAugusto Gil Ceballos Ceballos, Yisa María Ochoa Fuentes*, Ernesto Cerna Chávez, Arely Cano García
Received: 18/April/2024 – Published: 31/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2404-5
Abstract Background/Objective. Seed extracts from Canavalia ensiformis have shown both antiparasitic and repellent effects against pests. To evaluate the effectiveness of the extract combined with silicon dioxide nanoparticles (NPs) against Meloidogyne incognita eggs.
Materials and Methods. In vitro experiments were conducted to assess the effects of C. ensiformis seed extracts, alone and combined with silicon dioxide NPs, on M. incognita juveniles hatching. 150 eggs were used, and concentrations of 0, 2, 4, 6, 8, and 10 % of the extract were applied. Additionally, concentrations of the extract at 0, 1.5, 2.0, 2.5, and 3.0 %, each combined with NP concentrations at 0.06, 0.08, 0.10, 0.12, and 0.14 %, were evaluated.
Results. None of the treatments prevented more than 30 % of juveniles hatching. It was concluded that modifying the technique for obtaining C. ensiformis seed extract could have a complementary ovicidal effect; however, increasing the extract concentrations could serve as a medium for the proliferation of saprophytic fungi and other microorganisms.
Conclusion. The treatments did not show significant ovicidal effects.
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Figure 1. A: egg corresponding to the non-inoculated control and fixed with cotton blue (100). B: egg inoculated with Canavalia ensiformis extract and NPs (100X). C: amplified image of egg inoculated with C. ensiformis and NPs (100X). D: egg inoculated with C. ensiformis extract (100X).
Table 1. Means comparison of the effect of the treatments of the extract of Canavalia ensiformis seeds and silicon dioxide NPs on Meloidogyne incognita eggs.
Estimation of losses caused by Potato virus Y in potato crop in Coahuila
byJoel De Santiago Meza*, Gustavo Alberto Frías Treviño, Luis Alberto Aguirre Uribe, Alberto Flores Olivas
Received: 05/April/2024 – Published: 30/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2404-2
Abstract Background/Objective. The objective was to experimentally evaluate the losses caused by PVY in the Fianna variety potato crop and, consequently, estimate the losses caused by this virus in the potato-producing area of Coahuila.
Materials and Methods. Furrows of an experimental plot planted with potato seedling and seed-tuber, were mechanically inoculated with PVY at 20, 40, 60 and 80 days after emergence. The tubers produced were harvested and losses in each treatment were evaluated. Additionally, in four commercial potato fields in this same state, leaflet samples were taken at 20, 40, 60 and 80 days after the emergence, and the percentage of plants infected with PVY was evaluated by ELISA tests. Loss data from the experimental plot and incidence data from the farms were used to develop a statistical model to estimate losses caused by PVY in the Coahuila region.
Results. Yield losses due to PVY in the experimental plot were 9.4% to 53%. The percentage of incidence of infected plants in commercial properties varied from 0% to 100%. The model that best fit the data obtained was Berger's Y=1/[1+e (-{ln[yo/(1-y0)]+r*dae})]. The estimated losses in the Coahuila region in the 2022 cycle were 18%, equivalent to $19 068500.
Conclusión: This information highlights the importance of using certified PVY-free seed and protecting the crop from emergence until 60 DAE.
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Figure 1. Yield per hectare of Fianna potato plants in Assay 1.
Figure 2. Left: plants grown from tuber seed infected with PVY; right: plants grown from PVY-free tuber seed.
Figure 3. Yield per hectare of plants grown from infected tuber seed (0), plants inoculated at 20, 40, 60, and 80 DAE, and healthy plants (remained healthy throughout the 120-day cycle).
Figure 4. Fit of the Berger model explaining 98% of the variation in losses relative to the date of PVY infection (days after emergence - DAE).
Figure 5. Quantity and quality of tubers produced by plants grown from infected tuber seed (0), plants inoculated at 20, 40, 60, and 80 days after emergence (DAE), and healthy plants.
Figure 6. Tubers produced by: A) plants grown from infected tuber seed; B) plants inoculated at 20 DAE; C) plants inoculated at 40 DAE; D) plants inoculated at 60 DAE; E) plants inoculated at 80 DAE; F) healthy plants (no inoculation).
Table 1. Percentage of infected plants in commercial fields; ha = hectares, No. Samples = number of samples per field, DAE = days after emergence, No. Leaflets = number of leaflets.
Table 2. Estimated yield and economic losses in the potato-producing region of Coahuila.
Molecular aspects of phaseolotoxin biosynthesis produced by Pseudomonas syringae pv. phaseolicola
byAlejandra Chacón López, José Luis Hernández Flores, Efigenia Montalvo González, Selene Aguilera Aguirre*
Received: 20/August/2024 – Published: 30/December/2024 – DOI: https://doi.org/10.18781/R.MEX.FIT.2308-2
Abstract Background/Objective. Phaseolotoxin is produced by one of the most important and studied phytopathogens in the agricultural area: Pseudomonas syringae pv. phaseolicola. This bacterium causes halo blight, a disease that devastates the bean crop. The success of P. syringae pv. phaseolicola is related to its genetic information, which allows it to synthesize deleterious metabolites for its host, such as phaseolotoxin. This research aimed to analyze the molecular basis of the mechanism of action, immunity, genetics involved in the biosynthesis of phaseolotoxin, molecular diagnostic strategies, and molecular techniques developed in Mexico to manage bean halo blight.
Materials and Methods. The search and analysis of the most relevant scientific information regarding the biosynthesis of phaseolotoxin and the molecular studies of the pathogenicity and virulence factors of P. syringae pv. phaseolicola has contributed to the development of molecular strategies focused on the diagnosis and management of halo blight in beans.
Results. P. syringae pv. phaseolicola produce phaseolotoxin, responsible for forming the chlorotic halo characteristic of halo blight, this toxin is an inhibitor of OCTase, an enzyme that participates in the arginine synthesis pathway in beans. The Pht and Pbo chromosomal regions contain genes involved in the synthesis and immunity of phaseolotoxin, and the expression of these genes is regulated by the GacS/GacA system and temperature. The identification of genes involved in the synthesis of pathogenicity and virulence factors, such as phaseolotoxin, has allowed the development of strategies for diagnosis and management of the disease based on DNA amplification and the use of molecular markers that facilitate the identification of bean cultivars resistant to the pathogen.
Conclusion. Molecular studies have contributed to understanding how the phaseolicola pathovar produces phaseolotoxin. This information has been essential to understanding how bacteria have evolved from non-pathogenic to pathogenic variants. In addition, they provide information that allows the development of new strategies for timely diagnosis and contributes to strategies for managing halo blight.
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Figure 1. Symptoms produced BY P. syringae pv. phaseolicola ON bean. A Y B, Symptoms ON leaves. C Y D, Symptoms ON pods. Source: Adapted FROM Schwartz, (2008); Harveson, (2009).
Figure 2. Phaseolotoxin structure and PSOrn, product of phaseolotoxin degradation by plant peptidases.
Figure 3. Graphic representation of the Pht and Pbo Regions on P. syringae pv. phaseolicola chromosome. A, Pht Region operons. B, Pbo Region operons. Each arrow represents one gene, the direction of the arrow indicates the direction of transcription.
Figure 4. Model of signaling and regulation of phaseolotoxin biosynthesis in P. syringae pv. phaseolicola NPS3121. Temperature is sensed by the GacS membrane sensor, which autophosphorylates therefore (1). Phosphorylated GacS transfers phosphate to the response regulator GacA (2). GacA controls the expression of pht genes, mediated by the IHF regulator. GacA also controls the transcription of the pbo genes (3). Finally, phaseolotoxin is synthesized, which inhibits bean OCTase and prevents the synthesis of arginine. Consequently, the chlorotic halo develops.
Figure 5. Representative map of the distribution of P. syringae pv. phaseolicola in Mexico. The states marked with yellow color indicate the presence of this bacteria.
Table 1. Function of pht genes involved in phaseolotoxin synthesis.
Table 2. Prediction of the function of pbo genes involved in the phaseolotoxin synthesis.
Table 3. Oligonucleotides used to identify strains of P. syringae pv. phaseolicola producing phaseolotoxin.