Eduardo Raymundo Garrido Ramírez

Background. Chili pepper (Capsicum spp.) cultivation extends throughout Mexico, hosting a wide variety worldwide. However, crop health is reduced by the incidence of pathogenic microorganisms such as those of the Fusarium genus, which is one of the main agents causing vascular wilt and mortality of plant species. The use of molecular tools allows for rapid and reliable identification of organisms at the species level and help characterize the symptoms and pathogenicity they cause in hosts, which is important for field management and control. Objective. To identify at the molecular level fungal strains isolated from Siete Caldos chili (C. frutescens) using ITS and evaluate their pathogenicity in C. frutescens and C. chinense. Methodology. Strains of Fusarium from chile Siete Caldos plants (C. frutescens L.) were isolated and identified using traditional techniques (humid chamber and isolation in specific culture media) and molecular techniques (ITS1 and ITS4), and their pathogenicity in C. chinense Jacq. and C. frutescens was evaluated. Results. Seven strains were identified using taxonomic keys denoted as: 44hp, 45ta, 46ta, 46hp, 47hp, 45hpssc and 45hpmcsc. From the amplified regions, the phylogenetic tree was obtained using the maximum-likelihood method based on the comparison of ITS sequences. The fungal isolates were identified and grouped, which corresponded to F. oxysporum strains reported in the NCBI database. The pathogenicity test showed the presence of symptoms in C. frutescens, with strain 45ta being the most virulent (80 % incidence in inoculated plants). However, under the evaluation techniques used, C. chinense plants did not present wilting symptoms. Implications. The higher incidence of strain 45ta in C. frutescens could be due to the affinity of F. oxysporum for its host (Siete Caldos chili), while the absence of symptoms in C. chinense could be due to an asymptomatic infection. Conclusions. The isolated strains showed no variability in their molecular identification, but not all showed the same infective capacity in the pathogenicity test. Therefore, it is necessary to perform tests with greater specificity to determine whether subspecies of the studied isolates exist.

This study evaluates the mycoremediation potential of wild mushroom species from Chiapas, Mexico, specifically for high copper concentrations. Nine fungal carpophores were collected from tropical forests near coffee plantations. The morphological characteristics of the fungal strains and fruiting bodies were analyzed. Each specimen was identified through sequencing using the ITS₁ and ITS₄ primers. The ability to tolerate different concentrations of copper was evaluated by determining the fungal mycelial growth inhibition potential. Copper bioaccumulation by the fungi was quantified using biosorption assays with atomic absorption spectrophotometry. The enzymatic activity of laccase, lignin peroxidase, and manganese peroxidase from the fungal species was also determined in the presence of copper. Phylogenetic analysis identified the fungal species as Agaricus bisporus, A. subrufescens, Calvatia fragilis, Ganoderma coffeatum, G. lucidum, Pleurotus djmor, P. floridanus, Trametes elegans, and T. versicolor, all classified within the Agaromycetes class. The nine fungal species exhibited varying abilities to tolerate Cu²⁺ concentrations from 30 to 100 mg L⁻¹. At 30 and 60 mg L⁻¹ Cu²⁺, the G. lucidum H14-35 strain demonstrated the highest biosorption capacity, reaching 76.97%. Overall, the mushrooms in this study showed strong Cu²⁺ tolerance and biosorption, making them promising biomaterials for remediating copper-contaminated soils.

Mango anthracnose in mango in the tropical and subtropical regions of Mexico is a disease that induces serious economic losses, caused by Colletotrichum gloesporioides. The objective of this research was to determine the efficiency of integrated management for anthracnose control and to identify the critical moment for disease management. The work was carried out on cv. ‘Ataúlfo’, in Guerrero, Mexico, in three production cycles. The identification of the pathogen was confirmed and during a period of 11 months the abundance of spores in the canopy of the trees was examined. Three treatments were evaluated: integrated management with severe pruning (MIM-Pruning), integrated management without severe pruning (MIM) and Control treatment. The climate was conducive to the development of the disease (>80% incidence). The greatest increase in spores, with 65.9 to 84.1 spores/week, was observed during summer vegetative growth, in the phase of flowering and fruit set on the rachis, with its subsequent decrease in fruit growth. The MIM-Pruning and MIM treatment showed consistent results of less area under the disease curve progress (AUDCP), in foliage and flowering, causing a greater definitive fruit set per inflorescence and marketable fruits per tree with respect to the Control (P ≤0.05). Field pathogen population management should begin with the spraying of fungicide products in the summer vegetative growth phase and before the full flowering stage. Pruning is a practice that should be included in anthracnose management.

The essential oils of plants of the genus Piper have secondary metabolites that have antimicrobial activity related to their chemical composition. The objective of our work was to determine the chemical composition and evaluate the antifungal activity of the aerial part essential oil of P. auritum obtained by hydrodistillation on Fusarium oxysporum and Fusarium equiseti isolated from Capsicum chinense. The antifungal activity was evaluated by direct contact and poisoned food tests, and the minimum inhibitory concentration (MIC₅₀) and maximum radial growth inhibition (MGI) were determined. The identification of oil metabolites was carried out by direct analysis in real time mass spectrometry (DART-MS). By direct contact, the essential oil reached an inhibition of over 40% on Fusarium spp. The 8.4 mg/mL concentration showed the highest inhibition on F. oxysporum (40–60%) and F. equiseti (>50%). The MIC₅₀ was 6 mg/mL for F. oxysporum FCHA-T7 and 9 mg/mL for F. oxysporum FCHJ-T6 and F. equiseti FCHE-T8. DART-MS chemical analysis of the essential oil showed [2M-H]⁻ and [M-H]⁻ adducts of high relative intensity that were mainly attributed to eugenol and thymol/p-cimen-8-ol. The findings found in this study show a fungistatic effect of the essential oil of P. auritum on Fusarium spp.

La jamaica (Hibiscus sabdariffa) es afectada por severas enfermedades como tizón y manchado del cáliz (MCJ). El objetivo fue estudiar las relaciones entre fluctuación estacional de esporas de Corynespora y Coniella patógenos del manchado y tizón de cálices y hojas, las condiciones de clima y severidad (MCJ) en Ayutla, Gro., México. Las esporas fueron monitoreadas en dos ciclos, se aislaron los hongos y se realizó la identificación morfológica y molecular de Coniella el estudio se centró en patógenos reportados en México. Las pruebas de patogenicidad con C. diplodiella y C. cassiicola confirmaron la sintomatología muy similar entre ambos hongos. Coniella fue el más abundante (48%) y con menos cantidad Corynespora (8.7%). La dinámica de esporas tuvo una fluctuación mensual y relacionada con el clima. Las temperaturas máximas y medias (°C) y promedio de radiación global (W/m2) mostraron correlaciones positivas significativas con la abundancia de esporas de Coniella y el total de esporas, mientras que la precipitación (mm), temperatura mínima, velocidad del viento máxima (Km h-1) y horas de radiación solar, sus relaciones fueron negativas con las fluctuaciones de esporas de Corynespora. La severidad del manchado de hojas y cálices fue correlacionada positiva y significativa con el número de esporas capturadas.

Black Sigatoka is the main constraint to banana production worldwide, and epidemic outbreaks are continuously causing huge losses. Successful management of diseases requires a profound knowledge of the epidemiological factors that influence disease dynamics. Information regarding alternative hosts of Pseudocercospora fijiensis, the causal agent, is still very scarce. To date, only Heliconia psittacorum has been reported as an alternative plant host, and we hypothesized that other plants can house P. fijiensis. In the present report, ten plant species with suspicious leaf spots were collected inside and around commercial banana crops in Mexico. Diagnostic PCR gave positive amplification for six of these plant species, and DNA sequencing confirmed the presence of the pathogen in four. This is the first report of the presence of P. fijiensis in unrelated plants and it represents a breakthrough in the current knowledge of black Sigatoka. This finding is very important given the polycyclic nature of this disease whose successful management requires the control of initial inoculum to minimize epidemic outbreaks. The results presented herein can be used to introduce innovations in integrated black Sigatoka management programs to reduce initial inoculum, and help the international initiative to reduce the use of fungicides in banana production.

En el municipio de Arriaga Chiapas, desde el año 2009 se ha observado la muerte de plantas de piñón (Jatropha curcas L.) de 1 y 2 años de edad, con síntomas de marchitez y pudrición basal del tallo. La incidencia registrada ha sido de hasta 85%; la virulencia del patógeno es muy alta ya que ocasiona la muerte de la planta en un lapso de 20 y 30 días. El presente trabajo se realizó en los años 2011 a 2013, para la determinación del agente causal presuntivo. Se realizaron en laboratorio aislamientos en medio B de King (BK) y cloruro de trifenil tetrazolio (TTC), posteriormente los aislamientos fueron sometidas a pruebas bioquímicas y pruebas de hipersensibilidad en tabaco (Nicotiana tabacum L.) cv. Xanthi. Los resultados obtenidos dieron positivos en cinco cepas a Ralstonia solanacearum (E. F. Smith 1896) Yabuuchi et al., 1993.

The BV1 gene of the bipartite Begomovirus genome encodes a nuclear shuttle protein (NSP) that is also an avirulence determinant in common bean. The function of the NSP of two common bean-infecting bipartite begomoviruses, Bean dwarf mosaic virus (BDMV) and Bean golden yellow mosaic virus (BGYMV), was investigated using a series of hybrid DNA-B components expressing chimeric BDMV and BGYMV NSP, and genotypes of the two major common bean gene pools: Andean (cv. Topcrop) and Middle American (cvs. Alpine and UI 114). BDMV DNA-A coinoculated with HBDBG4 (BDMV DNA-B expressing the BGYMV NSP) and HBDBG9 (BDMV DNA-B expressing a chimeric NSP with the N-terminal 1 to 42 amino acids from BGYMV) overcame the BDMV resistance of UI 114. This established that the BDMV NSP is an avirulence determinant in UI 114, and mapped the domain involved in this response to the N-terminus, which is a variable surface-exposed region. BDMV DNA-A coinoculated with HBDBG10, expressing a chimeric NSP with amino acids 43 to 92 from BGYMV, was not infectious, revealing an essential virus-specific domain. In the BGYMV background, the BDMV NSP was a virulence factor in the Andean cv. Topcrop, whereas it was an avirulence factor in the Middle American cultivars, particularly in the absence of the BGYMV NSP. The capsid protein (CP) also played a gene pool–specific role in viral infectivity; it was dispensable for infectivity in the Andean cv. Topcrop, but was required for infectivity of BDMV, BGYMV, and certain hybrid viruses in the Middle American cultivars. Redundancy of the CP and NSP, which are nuclear proteins involved directly or indirectly in viral movement, provides a masking effect that may allow the virus to avoid host defense responses.

The capacities of the begomoviruses Bean dwarf mosaic virus (BDMV) and Bean golden yellow mosaic virus (BGYMV) to differentially infect certain common bean (Phaseolus vulgaris) cultivars were used to identify viral determinants of the hypersensitive response (HR) and avirulence (avr) in BDMV. A series of hybrid DNA-B components, containing BDMV and BGYMV sequences, was constructed and coinoculated with BDMV DNA-A (BDMV-A) or BDMVA-green florescent protein into seedlings of cv. Topcrop (susceptible to BDMV and BGYMV) and the BDMV-resistant cvs. Othello and Black Turtle Soup T-39 (BTS). The BDMV avr determinant, in bean hypocotyl tissue, was mapped to the BDMV BV1 open reading frame and, most likely, to the BV1 protein. The BV1 also was identified as the determinant of the HR in Othello. However, the HR was not required for resistance in Othello nor was it associated with BDMV resistance in BTS. BDMV BV1, a nuclear shuttle protein that mediates viral DNA export from the nucleus, represents a new class of viral avr determinant. These results are discussed in terms of the relationship between the HR and resistance.