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Búsquedas previas al 2023, Núm. 3. En la sección Volúmenes 30 - 41 (2012 - 2023).
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byAbimael Rubio Sosa, Misael Martínez Bolaños, Juan Florencio Gómez Leyva, Salvador Lozano Trejo*, Ernesto Castañeda Hidalgo, Gustavo Omar Diaz Zorrilla
Received: 30/August/2024 – Published: 26/March/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2307-1
Abstract Background/Objective. The objective of the study was to isolate and characterize native isolate of Trichoderma from organic crops of Arabica coffee (Coffea arabica) in Oaxaca state, as well as to evaluate their in vitro biocontrol potential against Colletotrichum spp., causal agent of anthracnose.
Materials y Methods. Soil and vegetative material samples were collected from coffee plant plots, from which fungal strains corresponding to the genera Trichoderma and Colletotrichum were isolated. Macroscopic and microscopic characterization was performed and the growth rate of each of the isolates was evaluated. Finally, molecular characterization was performed by sequencing the ITS region of rRNA. To evaluate the biocontrol potential, antagonism tests were performed between the isolates of the two genera.
Results. Seven different species were identified: T. harzianum, T. pleuroticola, T. sulphureum, T. tomentosum, T. koningii, T. spirale and T. lentiforme. The latter were the most abundant. Of these, T. lentiforme was selected and evaluated for its in vitro inhibition capacity against three Colletotrichum spp. It was observed that the growth of the fungus was inhibited by 20 to 80%.
Conclusion. The potential of Trichoderma as a biocontrol agent for Colletotrichum spp. is highlighted, acting in different ways against this phytopathogen. This contributes to the knowledge about the diversity of native Trichoderma species, to the coffee-growing region of the state of Oaxaca. In addition, this deeper knowledge contributes to enriching knowledge and choosing these species for future studies in the biocontrol of phytopathogens, in order to promote sustainable agricultural practices.
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Figure 1. Macroscopic characterization of 12 Trichoderma isolates on PDA.
Figure 2. Macroscopic characterization of three Colletotrichum Isolates on PDA.
Figure 3. Phylogenetic tree. A) PCR amplification products of the ITS region of rDNA using the universal primers ITS1 and ITS4, yielding approximately 620 bp. B) Phylogenetic relationship of 12 Trichoderma isolates inferred from rDNA sequence analysis (ITS1, 5.8S, and ITS2). The numbers at the nodes represent the bootstrap percentage based on 1,000 replicates.
Figure 4. Phylogenetic relationship dendrogram of 10 Colletotrichum isolates.
Figure 5. Dual confrontation between Trichoderma spp. isolates (T13, T14, and T15) and Colletotrichum spp. isolates (Z1, 108, and 112). The numbers below the isolates represent the PICR (percentage of radial growth inhibition).
Table 1. Characterization and growth rate of different Trichoderma spp. Isolates.
byTabita Queren Pérez Reyes, Santos Gerardo Leyva Mir, Mario Pérez Grajales*, María Teresa Martínez Damián, Rogelio Castro Brindis
Received: 30/August/2024 – Published: 08/March/2025 – DOI: https://doi.org/10.18781/R.MEX.FIT.2408-5
Abstract Background/Objective. Phytophthora capsici causes losses of up to 100 % in Capsicum pubescens and there are no resistant commercial varieties. A viable and sustainable alternative is to use the CM-334 rootstock (Capsicum annuum), which is universally resistant to Phytophthora capsici.
Materials and Methods. The following was studied: the root biomass of CM-334 when grafting the mazano chili hybrids ‘Maruca’, ‘Jhos’, and ‘Dali’, the resistance of the graft to P. capsici in infested soil and its yield (hybrid ‘Dali’), and the root biomass of CM-334 with applications of auxins and T. harzianum.
Results. As a rootstock, CM-334 exhibited 50, 53 and 75 % less root volume, fresh weight, and dry weight, respectively, compared to non-grafted hybrids. Using the CM-334 rootstock, there was no incidence of P. capsici and the yield decreased by 2 %, and even with T. harzianum, alone or in combination with 1200 ppm of IBA, the yield increased by 8 %. The grafted ‘Dali’ hybrid had 32, 50, 50, and 76 % less root length, volume, fresh weight, and dry weight, respectively, compared to the non-grafted hybrid; therefore, it is suggested to apply 1.25 kg ha-1 of T. harzianum and 1200 ppm of IBA every 20 days to improve root biomass.
Conclusion. Grafting manzano chili onto CM-334 is a viable and sustainable control alternative to reduce P. capsici incidence since none of the grafted plants showed wilt symptoms like the non-grafted ones, and the yield was the same as in the first production cycle, with the advantage that grafted plants produce more cycles (4 years), whereas the non-grafted ones die during the first cycle because of the oomycete.
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Table 1. Root volume, fresh weight, and dry weight of manzano chili plants of the hybrids ‘Maruca,’ ‘Jhos,’ and ‘Dali’ grafted onto CM-334 vs. non-grafted plants grown in Chapingo, Mexico. 2017–2019 cycle.
Table 2. Means of fruit number, fruit weight per plant, and yield per hectare of manzano chili plants grafted onto CM-334 vs. non-grafted plants, with and without the application of IBA and T. harzianum, grown in Chapingo, Mexico. 2020 2021 cycle.
Table 3. Root biomass of non-grafted and CM-334-grafted manzano chili plants, with and without the application of IBA and T. harzianum, in Chapingo, Mexico. 2020–2022 cycle.
Figure 1. Arbitrary scale for evaluating the incidence and severity caused by P. capsici in ‘Dali’ hybrid manzano chili (Capsicum pubescens) plants grown in pots with P. capsici-infested soil. Chapingo, Mexico, 2020–2021.
Figure 2. Root of non-grafted vs. CM-334-grafted manzano chili hybrid grown in hydroponics and greenhouse conditions in Chapingo, Mexico (2017–2019). A) Maruca, B) Maruca grafted, C) Jhos, D) Jhos grafted, E) Dali, F) Dali grafted.
Figure 3. A) Bipapillate sporangium and smooth mycelium; B) Unipapillate sporangium with zoospores of P. capsici obtained from infested soil in Chapingo, Mexico.
Figure 4. Area under the disease progress curve (AUDPC) of P. capsici in manzano chili plants grown in Chapingo, Mexico, from 2020 to 2021. dat: days after transplantation. D: non-grafted ‘Dali’ hybrid, d: days (application frequency). zSame letters indicate no statistically significant differences (Fisher’s LSD, P≤0.05).
Figure 5. Morphological characterization of P. capsici in diseased plants. A) cottony growth, B y C) bipapillate sporangium of P. capsici in manzano chili in Chapingo, Mexico.
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.