Backgrounds/Objective. Coffee cultivation is at risk due to the effects of climate change, which has created favorable conditions for the proliferation of diseases such as coffee leaf rust (Hemileia vastatrix). One of the most cost-effective and efficient control measures has been the use of materials that are tolerant or resistant to this fungus. The objective of this study was to analyze the response of 32 promising Coffea arabica accessions to coffee leaf rust and to describe their morphological characteristics, relating them to disease severity, under conditions prevailing in the municipality of Amatlán de los Reyes, Veracruz. Experimental development. A total of 32 C. arabica accessions were evaluated in a completely randomized block design with three replications, compiling a descriptive profile of the visible, identifiable, and measurable morphological traits of each evaluated accession. The incidence of coffee leaf rust (Hemileia vastatrix) was assessed on a five-level severity scale on a monthly basis over a two-year period. An ordinal mixed-effects model and post hoc tests were computed to identify significant differences in rust incidence. Hierarchical cluster analysis was carried out to group the materials according to susceptibility or severity level, and the relationship between morphological traits and infestation level was analyzed using multiple correspondence analysis. Results. The materials showed significant differences in tolerance to coffee leaf rust. Tukey's test (α = 0.05) identified three groups based on the severity of rust damage; the Pacamara variety was the most affected, while the H1 Centroamericano, Parainema, Catigua MG2, Col 1, EC 15, IPR 103, Kartila 1, Lempira, Paraíso, S795, and the Arabusta SLN 5B varieties were the least affected. The remaining varieties showed an intermediate severity of infestation. Conclusion. Under the conditions prevailing at the experimental site of the Colegio de Postgraduados Campus Córdoba, 11 C. arabica materials showed a favorable response to the severity of Hemileia vastatrix (H1 Centroamericano, Parainema, Catigua MG2, Col 1, EC 15, IPR 103, Kartila 1, Lempira, Paraíso, S795, and the Arabusta SLN 5B). This contributes to the options available to coffee growers in terms of production and plant health management against coffee leaf rust.
Background/Objective. Cucurbits are an economic pillar of global and national agriculture. However, their productivity is threatened by the increasing incidence of viral plant diseases. Consequently, coinfections with members of the Begomovirus and Crinivirus genera have been associated with exacerbated symptoms and high incidence rates in crops, leading to emerging disease patterns. The aim of this study was to identify and molecularly characterize the begomoviruses and criniviruses associated with an emerging disease in melon crops in a municipality of the Comarca Lagunera region, Mexico. Materials and Methods. A targeted sampling of nine melon plants exhibiting symptoms such as severe interveinal chlorosis, mottling, yellow mosaic patterns, and fruit deformation was carried out. For viral detection, DNA extraction was performed using 3% CTAB and RNA extraction using the TRIzol reagent. Begomoviruses and criniviruses were detected using PCR and RT-PCR with specific primers. Complete begomovirus genomes were enriched by rolling circle amplification (RCA). Amplicons derived from Open Reading Frame (ORF) of the capsid protein (CP) of criniviruses were generated using RT-PCR. Subsequently, the genomes and CP amplicons were cloned and sequenced for phylogenetic and evolutionary analysis. Results. Molecular identification revealed the prevalence of mixed infections in seven of nine samples, comprised of two begomovirus species, cucurbit leaf crumple virus (CuLCrV, Begomovirus cucurbitae) and watermelon chlorotic stunt virus (WmCSV, Begomovirus citrulli), and the crinivirus cucurbit yellow stunting disorder virus (CYSDV, Crinivirus cucurbitae). Genomic analyses confirmed that CuLCrV and WmCSV possess genomic structure typical of begomoviruses. Significant divergence was observed at specific loci (CuLCrV C4 gene, WmCSV NSP gene, and DNA-B intergenic regions of both species), suggesting their potential involvement in evolutionary adaptation processes. Phylogenetically, although the CuLCrV isolate showed close relationship to isolates from Arizona and Sonora, it was placed in a clade distinct from those previously reported in the region, indicating an independent evolutionary course. Furthermore, phylogenetic analysis based on the nucleotide sequence of the CYSDV capsid protein (CP) gene revealed a close relationship with isolates previously reported in Jordan and Mexico. Conclusions. This study represents the first report in Mexico of a disease associated with WmCSV, CuLCrV, and CYSDV coinfection in cucurbits. The findings amphasize the complexity of emerging diseases and highlight the importance of strengthening molecular epidemiological surveillance to mitigate the impact of these mixed infections on Mexican agriculture.
Background/Objective. Blueberry powdery mildew, associated with Erysiphe vaccinii, is a foliar disease that may cause defoliation and affect crop performance. In Peru, information on the foliar use of peracetic acid for its field management is limited. The objective of this study was to evaluate the effect of foliar applications of 15% peracetic acid on powdery mildew incidence in blueberry under field conditions in Ica, Peru. Experimental development. The trial was conducted in a commercial field of blueberry cv. Biloxi in Ica, Peru, using a randomized complete block design with five treatments: an untreated control and 15% peracetic acid at 2, 4, 6, and 8 mL L-1, with four replicates. Treatments were applied as foliar sprays twice, seven days apart, at a spray volume of 600 L ha-1. The response variable was the incidence of leaves with powdery mildew symptoms (under natural infection), assessed on seven dates from the first application onward. The presence of phytotoxicity symptoms was also visually recorded. Results. Before the first application, no differences were detected among treatments. After the first application, peracetic acid reduced powdery mildew incidence compared with the control, with initial efficacy of up to 67.7%. After the second application, the 4, 6, and 8 mL L-1 doses showed the best response, with maximum efficacies of 69.3, 78.0, and 79.7%, respectively. The 2 mL L-1 dose showed a lower effect. No visible phytotoxicity symptoms were observed at any of the evaluated doses. Conclusion. Under the conditions of this trial, 15% peracetic acid reduced foliar powdery mildew incidence in blueberry, with the best response at 4, 6, and 8 mL L-1 (69.3, 78.0, and 79.7%). These results indicate a favorable effect of the product under field conditions, although further evaluation in additional locations or growing seasons is needed for validation.
Background/Objective. Grapevine red blotch virus, GRBV (Grablovirus vitis) affects grapevine plants (Vitis vinifera) causing significant economic losses in vineyards. In Mexico, where GRBV has been reported in wine-producing regions such as Baja California, information on potential GRBV vectors remains limited. Although the three-cornered alfalfa hopper (Spissistilus festinus) is a confirmed vector in the USA, the role of other membracids in vineyards around the globe is still unclear. Recently, the Nearctic treehopper (Tortistilus wickhami) has been reported in Baja California, prompting this study to evaluate its potential for GRBV acquisition and transmission. Experimental development. Adult Nearctic treehoppers were collected from February to November 2023 in 20 vineyards in Valle de Guadalupe, Baja California. A total of 30 individuals were screened to detect GRBV by real-time PCR. In May 2024, 17 additional individuals were collected and used in transmission assays, with an acquisition access period of up to 4 days on GRBV-infected grapevine cv. Cabernet Sauvignon leaves, followed by an inoculation access period of up to 9 days on virus-free leaves. Both insects and recipient leaves were tested for GRBV by real-time PCR. Results. GRBV was detected in 6.7% (2/30) of the individuals collected in 2023, with positive insects only originating from vineyards confirmed as GRBV-positive. In the transmission assays, 53% (9/17) of the insects acquired viral particles after feeding on infected leaves; however, none of the recipient leaves showed detectable infection. Conclusion. This study demonstrates that the Nearctic treehopper, an insect phylogenetically close to, and morphologically resemblant of the three-cornered alfalfa treehopper (a confirmed GRBV vector), was able to acquire the virus in the field and in laboratory settings, but no transmission to recipient plants was proved under the tested experimental conditions in the laboratory.
Background/Objective. Plant species of the genus Eryngium are native to Mexico; their cultivation as ornamental cut flowers is a recent development, so the pathogens that affect them are largely unknown. In this context, a grower set out to innovate by using this plant as a cut flower but encountered a rot disease that decimated his field; therefore, the objective of this study was to isolate, identify, and characterize the causal agent of soft rot in the stems of Eryngium spp. Experimental development. Plants exhibiting rot symptoms were collected from a cultivated plot in the municipality of Ixtapan de la Sal, State of Mexico. From ten symptomatic plants kept in a humid chamber, a bacterium was isolated and identified using biochemical analysis. For molecular identification, DNA was extracted, and the 16S ribosomal gene was amplified with primers 27F and 1492R. PCR products were sent to the Advanced Genomics Laboratory at LANGEBIO, CINVESTAV Irapuato, Guanajuato. Koch’s postulates were also performed on twenty asymptomatic Eryngium spp. seedlings, which were inoculated by introducing a bacterial mass at the leaf base, the distal petiole, and the basal vein region. Results. Based on biochemical analysis, the bacterium was identified as belonging to the genus Pseudomonas; molecular analysis revealed that the bacterium was Pseudomonas putida. According to Koch’s postulates, 100% of the symptoms associated with soft rot were observed. Conclusion. Pseudomonas putida was confirmed as the causal agent of soft rot in Eryngium spp. Its pathogenicity was confirmed in Eryngium spp. seedlings according to Koch's postulates. This is the first report of P. putida causing this disease in these plants.
Background/Objective. Foliar chlorosis, short internodes, and curved petioles with purple streaks were observed in papaya (Carica papaya) crops (North and Atlantic regions) in Costa Rica since 2014. Identification of a putative plant virus associated with these symptoms was the aim of this research. Experimental development. Plant material was tested by ELISA (four plant viruses and potyviruses group), transmission electron microscopy (TEM), RT-PCR (degenerate primers for plant viruses), sequencing and phylogenetics. Results. All ELISA tests resulted negative. Bullet-shaped particles inside nuclei, and reticulum endoplasmic were only observed by TEM in symptomatic plants. Amplicons of 900 bp were consistently obtained from symptomatic samples using degenerate primers for plant rhabdoviruses. Nucleotide sequences showed 95.6 and 96.8% similarity to a putative papaya alphanucleorhabdovirus (Alphanucleorhabdovirus, Rhabdoviridae). Conclusion. This is the first report of a putative alphanucleorhabdovirus associated with symptomatic papaya plants showing streaked petiole (“pecíolo rayado”) disease in Costa Rica, but Koch’s postulates must be fulfilled and vector identified.
Background/Objective. Bioactive substances such as phosphites and silicon present a promising alternative for management of vascular wilt of tomato, due to their potential to inhibit pathogen growth and to induce plant defense mechanisms. The objective of this study was to evaluate the effect of three phosphite sources and a source of silicon on isolate Fol59 of Fusarium oxysporum f. sp. lycopersici race 2 via in vitro and in planta assays. Materials and Methods. In in vitro conditions, percentage of radial growth inhibition (PRGI) of isolate Fol59 was determined in PDA medium supplemented with each bioactive substance in concentrations between 10 and 20 000 ppm following a completely randomized design (4 × 9) with four treatments and nine different concentrations; five technical replicates and three biological replicates. In in planta conditions, the area under the disease progress curve (AUDPC) and efficacy percentage were evaluated with a completely randomized design (4 × 2) with four treatments and two different concentrations under four experimental conditions: control, inoculated control, treatments without inoculation and inoculated treatments. 20 experimental units and three biological replicates were used per treatment. Results. After seven days, the bioactive substances reduced radial growth of the fungus between 70 and 100% with significant differences among the concentrations. The largest inhibition was registered with silicon at 10 000 ppm (100%) followed by calcium phosphite at 2 000 ppm (99%). Fourteen days post inoculation, in in planta assays, the control showed 100% incidence and 98% severity. However, the potassium phosphite treatment (KPhi1) at 2 000 ppm reduced severity to 56%, which represents a 42% efficacy against the control. Conclusion. Phosphites and silicon showed inhibitory effect on mycelial growth of the fungus under in vitro conditions. In in planta assays, potassium phosphite at 2 000 ppm was the most effective treatment, reducing the severity of vascular wilt of tomato caused by Fol59.
Background/Objective. The genus Fusarium comprises some of the most important phytopathogenic fungi affecting maize crops. Fusarium cause diseases such as root, stalk, and ear rot, which negatively impact the crop's agricultural productivity. In the search for agrobiotechnological alternatives for controlling this fungus, this study was aimed to evaluate the antagonistic potential of Parkinsonia aculeata rhizobacteria against Fusarium spp. strains associated with native maize varieties from the Bajío region of Mexico. Experimental development. Two strains of Fusarium spp. (MC-03 and MC-05), isolated from roots of native maize varieties from the Bajío region of Mexico, exhibiting Fusarium wilt symptoms, were used. These fungi were tested in vitro against nine rhizobacteria of P. aculeata: Enterobacter cloacae (BA1), Priestia megaterium (BA4 and BA-7B), Sinomonas halotolerans (BA10-B), Staphylococcus warneri (BP5), P. endophytica (BP6), Bacillus subtilis (TP1 and TP2), and S. hominis (TM6). Microscopic and macroscopic characterization of the fungal strains and biochemical analysis of the rhizobacteria were performed. Radial growth inhibition of the fungal isolates was determined by triplicate dual fungus-rhizobacteria confrontations. A completely randomized design was used, analyzing the data obtained in the STATISTICA software using an ANOVA based on a linear model of fixed effects and a mean comparison test by DMS (p>0.05). Results. With the exception of P. endophytica (BP6), all rhizobacteria exhibited enzymatic activity related to fungal antagonism mechanisms. B. subtilis (TP1) produced glucanases, lipases, and proteases. Microscopic and macroscopic characterization of the fungal strains indicated that they belong to Fusarium spp. In the rhizobacteria-MC-03 confrontation, the B. subtilis bacterial strains (TP1 and TP2) were statistically similar and achieved the greatest inhibition of mycelial growth (23%). With the fungal strain MC-05, P. endophytica (BP6) and S. hominis (TM6) were statistically superior to the other rhizobacteria in inhibiting mycelial growth (17%), followed by the two B. subtilis strains (TP1 and TP2), which inhibited 10% and 17%, respectively. Conclusion. There was a significant variability in the mycelial growth response of the fungi to rhizobacteria. B. subtilis (TP1 and TP2), S. hominis (TM6), and P. endophytica (BP6) exhibited an antagonistic effect, inhibiting the mycelial growth of Fusarium spp. strains by up to 23% compared to the absolute and commercial controls. This study establishes the preliminary scientific basis for obtaining a biofungicide with specific inhibitory capabilities against the fungi studied.
Background/Objective. Citrus (Citrus spp.) production is affected annually by anthracnose, associated with Colletotrichum spp. This disease can occur preharvest and postharvest and is generally controlled with synthetic fungicides, which pose health problems for farmers and consumers, negatively impact the environment, and lead to the emergence of resistant phytopathogen populations. An alternative to these problems is the application of plant extracts with antifungal properties, which could contribute to the production of safe food. Therefore, the objective of this study was to evaluate the effect of plant extracts under in vitro conditions against Colletotrichum gloeosporioides, causal agent of anthracnose on grapefruit (Citrus paradisi). Materials and Methods. Extracts were obtained from 17 plant species. The effectiveness of the extracts was evaluated using the poisoned PDA culture technique (PDA + 10% plant extract), in which 5 mm diameter discs of the fungus were inoculated onto Petri dishes. The fungicide Benomyl (10%) was used as a positive control, and pure PDA as a negative control. A completely randomized experimental design with 19 treatments and three replicates was used. The percentage of inhibition of C. gloeosporioides mycelial growth was recorded when the negative control completely covered the surface of the Petri dish. Data were analyzed using the statistical software SAS version 9.0. Results. The best extracts were zopilote seed (Swietenia macrophylla), bull blood tree bark (Bocconia arborea), and bull blood tree leaf and stem (B. arborea), and moringa seed (Moringa oleifera), inhibiting the growth of C. gloeosporioides by 69.2, 67.5, 44.1, and 35.6%, respectively. The positive control, Benomyl, inhibited C. gloeosporioides growth by 100%. Conclusion: The best in vitro inhibitory effect on Colletotrichum gloeosporioides was obtained with Swietenia macrophylla seed extracts (69.2%), followed by Bocconia arborea bark (67.5%), B. arborea leaf and stem (44.1%), and Moringa oleifera (35.6%).
Background/Objective. Nematophagous mites represent a potentially effective tool in integrated management programs for plant-parasitic nematodes. The objective of this study was to evaluate the predatory capacity of the nematophagous mite Sancassania mycophaga against the plant-parasitic nematode Nacobbus aberrans under laboratory conditions. Experimental development. Two independent experiments were conducted. For this purpose, the experimental unit consisted of a pot with a pepper plant (Capsicum annuum), in which 500 or 1000 J2 juveniles of N. aberrans were inoculated. Four treatments were evaluated: (1) control (nematodes only), (2) simultaneous inoculation of mites and nematodes, (3) inoculation of nematodes five days after mites, and (4) inoculation of nematodes 10 days after mites. In all treatments, five mites were introduced per pot. The variables were: percentage of J2 penetration in roots, number of galls, eggs, and abundance of mites. The data were subjected to ANOVA and comparison of means (LSD, p < 0.05). Results. Twenty-one days after the establishment of the trials, a significant reduction in nematode penetration was observed in all treatments with mites, compared to the control. In the experiment with 500 J2, the percentages of root penetration were 1.0, 3.4, and 2.5% for treatments 2, 3, and 4, respectively. In the experiment with 1000 J2, the penetration percentage was 21.3 and 23.8% for treatments 2 and 3. From day 14 onwards, the mite population showed sustained growth, increasing from an initial five individuals to more than 25 at 21 days (>400%) and more than 35 at 45 days (>600%). No significant differences in the number of galls or eggs were detected at 45 days. Conclusions. S. mycophaga reduced the penetration of N. aberrans into pepper roots. With 500 J2, the relative reduction ranged from 42 to 83%, while with 1 000 J2 it varied between 42 and 49% compared to the control. In addition, the mite managed to establish itself and multiply in the experimental system. These results support its potential as a biocontrol agent for N. aberrans.
Justification. The use of chemical pesticides has been widespread for several decades, proving effective in controlling pests that reduce crop quality and productivity. However, due to their chemical nature, they present side effects that affect the health of the applicator, the consumer, and the environment. Therefore, the use of natural products is currently emerging as an alternative for controlling phytopathogenic diseases and pests. The objective of this research was to review and analyze the bactericidal and fungicidal effects of phytochemical-rich extracts obtained from agricultural and agro-industrial byproducts and waste. Theoretical and experimental framework. A literature review was conducted using Scopus and Web of Science, focusing on English- and Spanish-language publications from the last 10 years. Only publications related to the extraction of phytochemicals from agricultural and/or agro-industrial byproducts and that investigated their effect against phytopathogenic organisms were considered. In this regard, the main phytochemicals with antibacterial and antifungal activity are phenolic compounds such as flavonoids and other derivatives. Likewise, hydrophobic compounds such as terpenes (essential oils) have demonstrated biocidal potential at concentrations similar to those currently marketed. The main modes and mechanisms of action are multi-target, meaning they affect more than one metabolic pathway and organelle. For example, they affect the cell membrane by inserting into the lipid bilayer, reduce biofilm formation, reduce ergosterol synthesis, and attenuate chitin synthesis in the cell wall. Conclusions and Perspectives. Phytochemicals with potent bactericidal and fungicidal activity were identified, primarily phenolic compounds and essential oils (terpenes). These phytochemicals exhibited IC50 values and reduction percentages even higher than those of the chemical controls. Agricultural byproducts and biomass, which are undervalued resources, represent an important alternative for extracting value-added phytochemicals that can be used across multiple industries, including agriculture, to develop sustainable, non-toxic biopesticides.
Background/Objective. The cultivation of pitahaya (Selenicereus undatus) has expanded in recent years in Mexico. In 2023, symptoms of stem rot were observed in commercial pitahaya orchards in the state of Puebla. The objective was to characterize and identify the causal agent of stem rot, evaluate the pathogenicity of the causal agent in different pitahaya species as well as other plant species, and assess its in vitro sensitivity to commercial bactericide formulations. Materials and Methods. Ten rotten stems from Huitziltepec, Puebla, were analyzed. Tissue samples from each stem were disinfected and macerated in 500 µL of sterile distilled water; from there, 100 µL were seeded in Wilbrink's and King's B culture media. From the bacterial growth, strain CPHU23 was biochemically characterized and identified by multilocus sequence analysis (MLSA) and phylogenetic analysis of the rpoB, gyrB, leuS, and fusA genes. The pathogenicity of CPHU23 was evaluated by infiltration of 3 × 10⁸ CFU mL⁻¹ in five species of the genus Selenicereus: S. ocamponis, S. purpusi, Selenicereus sp. “Golden,” Selenicereus sp. “Solferina” and S. undatus, as well as in Agave cupreata, A. angustifolia, Aloe vera, Allium cepa, Solanum lycopersicum, and Capsicum annuum. In vitro sensitivity was determined by the disk diffusion method with 10 commercial bactericide formulations. Results. Three bacterial morphotypes were isolated from the 10 stems. The CPHU23 morphotype was the most common, with yellow, round colonies with smooth edges and a mucoid appearance. Biochemical characterization of the CPHU23 strain showed 93% similarity to Pantoea vagans. MLSA analysis phylogenetically grouped the CPHU23 isolate within the Pantoea vagans clade, phylogenetically related to the type strains of P. vagans LMG 24199, YI-1, and MA I6050 with bootstrap support greater than 85%. Inoculation with P. vagans CPHU23 caused stem rot in the five species of the genus Selenicereus, in leaves of A. cupreata and A. vera, but not in bulbs of A. cepa and fruits of S. lycopersicum and C. annuum. Pantoea vagans CPHU23 was sensitive in vitro to copper oxychloride, gentamicin sulfate, oxytetracycline hydrochloride, and streptomycin, but resistant to kasugamycin. Conclusion. Pantoea vagans is the causal agent of stem rot in pitahaya in Puebla. All five pitahaya varieties are susceptible to stem rot. Agave cupreata and Aloe vera could be potential hosts for P. vagans. The use of copper oxychloride may be an efficient management strategy for P. vagans in pitahaya cultivation in Mexico.
Background/Objective. Phytophthora capsici represents one of the most significant threats to pepper production worldwide, and its control relies predominantly on fungicide applications, which entail considerable environmental concerns. Therefore, exploring biological control strategies has become a relevant alternative. This study aimed to assess the potential of a bacterial isolate as a biocontrol agent against six P. capsici and one P. cinnamomi isolates. Materials and Methods. Biocontrol effects were assessed in vitro using dual-culture assays between the bacterial isolate JJR198 and Phytophthora isolates to evaluate inhibition of mycelial growth, sporangia formation, and zoospore release, with additional observations by scanning electron microscopy. The efficacy of JJR198 in suppressing Phytophthora root rot was evaluated in pepper plants under greenhouse conditions by measuring disease severity in inoculated plants. In addition, salt tolerance and persistence of the bacterium in the rhizosphere and rhizoplane were determined. All data were subjected to ANOVA followed by Tukey’s test (p ≤ 0.05). Results. Identified as Bacillus zhangzhouensis through 16S rRNA sequencing, the bacterial isolate JJR198, exhibited antagonistic activity. In vitro assays showed that strain JJR198 reduced mycelial growth by 42.0 to 52.7% across six tested Phytophthora isolates. The biocontrol activity depended on the initial bacterial concentration, as sporangia formation and zoospore release in the tested Phytophthora capsici isolates were completely suppressed at 1.0 × 10⁸ CFU mL-1, whereas no effect was observed at lower concentrations (1.0 × 10⁴ and 1.0 × 10⁶ CFU mL-1). Using optical and electron microscopy, it was observed that the hyphae and mycelia were covered by bacterial cells. However, in the in vivo evaluation, pretreatment of pepper plants with JJR198 (1.0 × 10⁸ CFU mL-1) at 7, 3, or 0 days before oomycete inoculation did not reduce disease severity caused by Phytophthora capsici. JJR198 also showed the ability to grow under high-salinity conditions, as it developed on NA medium containing 7.5% NaCl after 48 h of incubation at 30 °C. Additionally, the presence of the bacterial inoculum was confirmed in pepper roots: colonies with morphological characteristics identical to JJR198 were recovered from rhizosphere and rhizoplane samples, with counts of 1.6 × 10⁶ and 0.19 × 10⁶ CFU mL-1, respectively. Conclusion. The results indicate that Bacillus zhangzhouensis JJR198 exhibits in vitro antagonistic activity against multiple Phytophthora isolates, achieving mycelial growth inhibition ranging from 42.0 to 52.7%, as well as inhibition of sporangia formation and zoospore release at a concentration of 1.0 × 10⁸ CFU mL⁻¹. However, its effectiveness in planta remained limited under the conditions tested.
Background/Objective. Metabolites of castor bean (Ricinus communis), such as the alkaloid ricinine, have antibacterial properties with the potential to combat phytopathogenic bacteria such as Xanthomonas perforans, Acidovorax citrulli, Clavibacter michiganensis, and Ralstonia solanacearum, making it a natural alternative to conventional chemicals. Therefore, the objective of this study was to evaluate the antimicrobial activity of methanolic extracts from castor bean leaf accessions and quantify ricinine using HPTLC to determine its effectiveness as a bactericidal agent. Experimental development. The leaves of nine castor bean accessions were ground and sieved to prepare methanolic extracts coded as: 1+, 2+, 4+, 5+, 6+, 7+, 8+, 9+, and 10+. Ricinine in the extracts was quantified by HPTLC. To determine antibacterial activity, the phytopathogenic bacteria Xanthomonas perforans, Acidovorax citrulli, Clavibacter michiganensis subsp. michiganensis, and Ralstonia solanacearum were reactivated and cultured in selective medium with concentrations of the extracts at 100, 75, 50, and 25% and a chemical control Finalbacter® (Gentamicin Sulfate and Oxytetracycline Hydrochloride). The analysis was performed in triplicate. Results. The extracts identified as 2+ and 5+ proved to be the most effective, with inhibition halos of 18.94 mm and 17.23 mm, respectively. Ralstonia solanacearum showed the greatest inhibition (21.6 mm), followed by A. citrulli and X. perforans (19.26 mm each) and C. michiganensis subsp. michiganensis (12.21 mm). The 100% and 75% concentrations showed the largest inhibition halos (20.6 mm and 19.8 mm), compared to the lower concentrations and the chemical control. Ricinine concentrations ranging from 0.88 to 2.14 mg g⁻¹ were quantified. Conclusion. Accessions 2+ and 5+ of Ricinus communis showed potential as a natural option for controlling phytopathogenic bacteria, with an average inhibition zone of 19.31 mm and 17.92 mm, respectively.
Justification. Within the genus Alternaria, several phytopathogenic species stand out for causing diseases such as leaf spot and blight in hosts including fruit trees, cereals, vegetables, and ornamental plants, resulting in significant economic losses. Despite this issue, information on the genus Alternaria in Mexico is limited and scattered. Therefore, the objective of this review was to describe the current status of the genus Alternaria in Mexico through a compilation of published studies on the characterization of reported pathogenic species, the diseases they cause in plants, and the various control strategies employed. Theoretical and experimental framework. Traditional identification of the genus Alternaria is based on morphological characteristics observed in culture; however, intra- and interspecific variability limits its accuracy. Consequently, molecular tools such as PCR, sequencing, and phylogenetic analysis are used to distinguish species and establish more precise evolutionary relationships. In Mexico, this genus affects more than 20 agricultural and ornamental hosts across 15 states, causing diseases in chrysanthemum, papaya, cacti, broccoli, pepper, and tomato, with incidences exceeding 40% in some crops. Its management requires an integrated approach combining accurate diagnosis, rational use of fungicides, strategies based on crop phenology and inoculum density, and sustainable alternatives such as biological control, plant extracts, microalgae, and nanoparticles, which have shown high efficacy and reduced environmental impact. Conclusions and Perspectives. In Mexico, nine species have been reported affecting 23 cultivated hosts, although information gaps remain for ornamental, forest, and native species. The main challenges for their control stem from incorrect disease diagnosis, which limits the application of effective strategies.
Background/Objective. This study analyzed for the first time the asymptomatic condition induced by CLas in Citrus sinensis / C. aurantium based on initial reports in the Central Gulf region of Mexico. The objective was to analyze with a mechanistic approach the spatial-temporal concentration of CLas at the plant level in commercial orchards to demonstrate the possible implication of a prolonged incubation period in the asymptomatic expression of HLB. Materials and Methods. Two out of three trees (A1-A3) (>30 years old) of asymptomatic Valencia sweet orange trees positive for CLas, identified through official diagnostic protocols in San José Acateno, Puebla, were confined. On trees A2 and A3, 13 and 16 secondary branches were marked, with a total of 112 and 108 foliage/samples per month, respectively (total 646 samples), obtained from the distal and proximal parts of each branch. Seven monthly samplings of plant material were carried out between May and December. At the root level, three categories were sampled by diameter/function and by a combination of six distal trunk sectors (0 - 280 cm) by 4 in depth (0 x 110 cm) with a total of 111 samples. DNA extraction was performed with 2% CTAB and quantification by RT-qPCR (oligos, HLBp/HLBas). Results. In canopy, the incidence/branches in A3 was 52.2% (Ct = 22.7 – 34.9), and in A2 47.8% (Ct = 23.4 –35), with no statistical difference (p = 0.48). The inoculum load was 1.6 (±1.3) log-CLas, equivalent to 109 copies/reaction in 100 mL (range in number of copies 6.3 to 68,870.7). CLas did not differ between distal (1.6 log) and proximal (1.5 log) samples (p = 0.33). Significative temporal fluctuation was found between June and October in positive samples (37 – 87, p < 0.0001), but not in CLas concentration (1.6 – 3.5 log-CLas, p > 0.72). The distribution of CLas by branch had a temporal effect (p = 0.0001) and by sector (p = 0.07), showing high mobility and seasonality. The maximum concentration (Ymax) was associated with the middle-upper sector of the canopy, and high mobility towards the lower and upper sectors in Yinitial and Yfinal. In roots, 38.7% positivity was found. The detectability of CLas was homogeneous among root types (p < 0.0001) but variable in concentration (p = 0.04). The 47.6%, 15.4%, and 38.7% incidence was associated with 38.3, 43.4, and 9.5 average CLas copies for support, conduction, and absorption roots, respectively (p = 0.0001). Two sections with higher CLas intensity-concentration (80 – 144 copies) were associated with roots in the middle drip zone (160 – 240 cm) and medium depth strata (50 – 80 cm). Conclusion. CLas was significantly and consistently detected in plant and root tissue throughout the experimental period, but at fluctuating, non-incremental concentration, analogous between trees A2 and A3. The wide canopy-root distribution suggests a chronic systemic effect. Consequently, the incubation period does not determine the asymptomatic condition in the sweet orange/sour orange productive system investigated. Other factors, e.g. inherent to pathogen variability, could be involved. These results contribute to optimizing a surveillance-monitoring system considering seasonality, zone-branch, sector-canopy and type of tissue, with a greater probability of detection of CLas even in an eventual asymptomatic condition and generate new insights for Clas management.
Background/Objective. In strawberry (Fragaria x ananassa), the main commercial rosaceous fruit in Mexico, the occurrence of Neopestalotiopsis rosae (Ascomycota: Sporocadaceae) was recently reported in Michoacán. The objective was to analyze, using an etiological-epidemiological approach, the implication of two N. rosae ITS-haplotypes, associated to five isolates from strawberry and blackberry (Rubus sp.) selected for regional prevalence, in the pathogenesis, aggressivity, and inoculum load in strawberry cv. San Andreas. Materials and Methods. Three isolates of Haplotype 1 / Strawberry (H1): F142P40S, F6P35R, F17P34R, and two of Haplotype 2 (H2) / Blackberry: F142D93R and Z13P27R were cultured in V8 / 25° / 14 d until conidiomata formation, and in PDA / 25° / 7 d to obtain liquid and solid inoculum, respectively. Eight three-month-old strawberry plants cv. San Andreas were evaluated per isolate; two trifoliate leaves / 4 plants were inoculated with 4 mL spray 1 x 106 conidia mL-1, and 4 plants with 5 x 5 mm mycelium PDA-blocks per crown wound. Sterile water was sprayed on 8 control plants. Plants were kept in a semi-covered greenhouse. Starting at 72 hai, every 3 d / 3 months, the following variables were measured: Number of lesions (LN), Lesion diameter (LD), Number of sporulating lesions (EL), Plant height, Crown diameter, and Chlorophyll units SPAD 502 (CU). The incubation period (Pi), latency period (Pl), and generation period (Pg) were estimated for each haplotype. Temperature and RH were recorded every 30 min with HOBO U23. Pathogenicity was validated using Koch's postulates. Isolates H1 and H2 were confirmed culturally by ITS1 / ITS4. ANOVA, in split plots design, and Tukey (p = 0.05) were conducted in RStudio. Results. The five isolates of N. rosae were more infectious on leaves (p = 0.0001) but exhibited variable and significant aggressivity (p = 0.0001) on LN, EL, and LD, with expression of circular leaf lesions, light brown color, dark edge, and reddish halo on the upper and lower surface. H1 isolates were more pathogenic than H2 (e.g., 3504 vs. 270 LN / plant), with H1 - F142P40S being more aggressive (p = 0.05), with an average LN = 187.5 and EL = 8.45 at 2 and 26 days after inoculation (dai), respectively. In contrast, H2 - F142D93R and H2 – Z13P27R had LN = 20 and 25 at 87 and 95 dai, respectively, with a maximum average range of 0.19 - 0.37 EL > 73 dai. Similarly, in crown, all isolates were pathogenic, but with less aggressivity and no statistical difference. A reddish-dark discoloration and internal necrotic rot was observed in crown and low root density. H1 - F17P34R was conspicuous with a maximum NL = 20 and LE < 0.1 at 85 dai. In leaf, the speed of symptoms expression and sporulation rate, although variable, was higher in isolates H1 vs. H2, determined, respectively, by 2 vs. 4 dai Pi, 14 - 16 (3 d) vs. 33 - 40 (7 d) dai Pl, and 14 - 73 (59 d) vs. 33 - 56 (23 d) dai Pg. The crown infection was slower with 28 d Pi in both haplotypes. Contrasting aggressivity among isolates had no significant effect on plant height and crown diameter, but did have an effect on CU reduction, with a maximum of 14.5 in H1 - F142P40S compared to control. ITS of 33 isolates confirmed the H1 and H2 pathogenicity. Conclusion. Through significantly contrasting LN, EL, CU, Pi, Pl, and Pg, it was demonstrated the pathogenic variability of two N. rosae ITS-haplotypes, prevalent in Michoacán, obtained from strawberries and blackberries commercial cultivars. A novel mechanistic understanding of pathogenesis was addressed. It is reported for the first time that N. rosae isolates, associated with blackberries, were pathogenic to strawberries but with less aggressivity. Sustainable regional management must consider the variable capacity of the fungus and its interaction with other pathogens with vascular capacity.
Background/Objective. Papaya meleira disease in Mexico is associated to Papaya meleira virus Mexican variant (PMeV-Mx) and is characterized by the spontaneous exudation of latex in fruits. PMeV-Mx ORF2 encodes a protein with RNA-dependent RNA polymerase (RdRp) motifs, which is essential for viral replication. This study aimed to develop a method for producing and purifying recombinant PMeV-Mx ORF2 encoded protein (pORF2) in E. coli and generate specific antibodies for its detection. Materials and Methods. The PMeV-Mx genome was analyzed using UGENE to predict ORFs and identify the putative slippery site. ORF1 and ORF2 were amplified by PCR from cDNA obtained from infected papaya latex, cloned into pGEM-T Easy, and subsequently transferred into pDONR221 and pDEST17 for expression in E. coli. Recombinant 6xHis-pORF2 was expressed in E. coli BL21 strain, induced with IPTG, and purified under denaturing conditions. The purified protein was used to generate polyclonal antibodies, with immunizations conducted at different time points. Antisera specificity and optimal working dilutions were evaluated by immunodetection assays, using recombinant 6xHis-pORF2 as the target and His-tagged proteins as negative controls. Additionally, papaya plants were inoculated with latex from symptomatic fruits as virus reservoir and PMeV-Mx infection was confirmed by RT-PCR. Results. The recombinant 6xHis-pORF2 protein of PMeV-Mx was expressed in E. coli and purified. A ~46.5 kDa band was detected, consistent with its estimated molecular weight. The protein expression increased between 2- and 6-hours post-induction with IPTG. Western blot analysis confirmed the presence of the His-tag and the integrity of the recombinant protein. Purification using Ni-NTA resin resulted in a strong ~46.5 kDa band along with light bands ranging from 15 to 150 kDa. Polyclonal antibodies against pORF2 were generated and specifically recognized the purified protein in immunoassays, with detection observed at dilutions from 1:500 to 1:3000. No cross-reactivity was observed with negative controls, but a non-specific ~75 kDa band was detected in E. coli extracts. Conclusion. A protocol for expressing, detecting, and purifying the recombinant 6xHis-pORF2 protein from PMeV-Mx in E. coli was established. Rabbit polyclonal antibodies recognized the target protein in bacterial fractions, though further optimization is needed to enhance specificity. These antibodies will support future diagnostic development and protein characterization in plants.
Background/Objective. In the roselle (Hibiscus sabdariffa) producing area of the state of Guerrero, Mexico, plantations with a high incidence of calyx blight were detected. The aim of this study was to know the causal agent of this disease. Materials and Methods. Calyces with and without symptoms of the “Criolla de Guerrero”, “Sudán” and “China Negra” cultivars were gathered from the municipal areas of Ayutla and Tecoanapa, Guerrero. Out of the calyces with symptoms, different fungal strains were isolated, out of which two were selected to perform pathogenicity tests under greenhouse conditions and identified with the amplification and sequencing of the elongation factor -1α (EF-1α) with the primers EF1-728F/EF1-986R. Results and discussion. The sequences obtained were compared with the ones in the NCBI and Fusarium MLST databases and they corresponded with the Fusarium incarnatum-equiseti (FIESC) 16 and 17 species complexes, currently known as Fusarium sulawesiensis and Fusarium pernambucanum, respectively. In the pathogenicity tests, the inoculated strains induced similar symptoms to those observed in the field. The FIESC complex has been proven to produce the mycotoxin trichothecene. Therefore, studies to determine the presence of this toxin in roselle are required, considering that its main use is the preparation of refreshing beverages, which may be a health risk. Conclusion. This is the first report of Fusarium sulawesiensis and Fusarium pernambucanum as causal agents of the roselle calyx blight in Mexico and in the world.
Background/Objective. The production of tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) is affected by the nematodes Rotylenchulus reniformis and Meloidogyne enterolobii; however, the interaction between these two nematodes on these plant species is unknown. The aim of this study was to determine the interaction of R. reniformis and M. enterolobii in tomato and cucumber plants through artificial inoculations under greenhouse conditions. Materials and Methods. Twenty-one-day-old seedlings were inoculated with 2000 juveniles (J2) of each nematode per plant. The experiment followed a completely randomized three-factor design with six treatments: T1= R. reniformis; T2= M. enterolobii; T3= R. reniformis was inoculated and 15 days later M. enterolobii was added; T4 = M. enterolobii was inoculated and 15 days later R. reniformis was added; T5 = both species were inoculated on the same day; T6 = uninoculated control. The reproduction factor (RF) of both nematodes, galling index for M. enterolobii, and root necrosis percentage for R. reniformis were recorded at 30 and 50 days after inoculation. Results. In cucumber plants, M. enterolobii reduced its reproduction by up to 73% in the presence of R. reniformis, while in tomato plants, its reproduction decreased by 52%, with a reduction in the galling index of 72 and 60% in cucumber and tomato plants, respectively, compared to T1 and T2. On the other hand, R. reniformis reduced its reproduction by 72% in cucumber plants and 67% in tomato plants in the presence of M. enterolobii, and a reduction in symptom severity was observed by 78 and 77% in cucumber and tomato plants, respectively, compared to T1 and T2. Conclusion. In treatments where one species was inoculated before the other, the species inoculated first showed a higher RF and caused greater disease severity. In simultaneous co-inoculations, both nematodes reduced their RF and caused lower symptom severity in tomato and cucumber plants.
