RESUMEN: El arbolado urbano es un elemento esencial en la infraestructura de toda urbe. El Bosque San Juan de Aragón (BSJA) en la Ciudad de México está catalogado como un área verde de valor ambiental pero su condición respecto a la diversidad y estructura arbórea se ha estudiado poco. El propósito del presente trabajo fue aplicar los procedimientos del Indicador Diversidad y Estructura, en el área verde urbana, Bosque San Juan de Aragón de la Ciudad de México, y contribuir en el diagnóstico sobre el estado actual de salud en esta materia.

Las áreas verdes urbanas aportan diversos servicios a la sociedad y al ambiente. El Bosque San Juan de Aragón, es una de las pocas áreas verdes al noreste de la Ciudad de México y la condición actual de su arbolado en materia de salud no se conoce con precisión. En el presente estudio se implementó y adaptó el protocolo del indicador condición de copa en 28 parcelas circulares de 0.1 ha, establecidas aleatoriamente en el bosque mencionado. A todos los árboles dentro de cada parcela, se les midió el diámetro normal (DN) y altura total (At), se determinó su clasificación taxonómica, condición de copa y densidad de plantación. Para condición de copa, seis variables fueron medidas: proporción de copa viva (Pcv), densidad de copa (Dnc), transparencia de copa (Trc), muerte regresiva (Mrg), posición de copa (Pco) y exposición a la luz (Exl). Las primeras cuatro se midieron en clases de 5% y las dos restantes a través de una escala ordinal. Se evaluaron 760 árboles, agrupados en 10 familias, 11 géneros y 12 especies. Los valores promedio para las variables de copa fueron, 56.37% Pcv, 44.38% Dnc, 4.04% Mrg y 38.4% Trc. Solo la Pcv alcanzó los estándares establecidos de salud arbórea encontrados en otros estudios, mientras que las Dnc fueron bajas y los valores de TrC y Mrg altos.

No abstract

Nanche (Byrsonima crassifolia) has great economic importance in the dry and humid tropics in Mexico, where is used for the elaboration of different drinks, foods, and candies; also in the traditional medicine to treat fever and stomach disorders. Since 2021, a high incidence of disease-causing scabby fruit in young nanche fruits has been detected in Las Choapas, Veracruz, Mexico. Disease symptoms were visible on the skin of fruits which progressed as fruits matured. Therefore, the objectives of this study were to identify the causal agent of this scab disease based on morphology and molecular techniques and to determine their pathogenicity. Fifteen isolates were recovered from diseased fruits. Because the isolates presented similar morphology, two of them were selected to determine their identity and pathogenicity. On the basis of colony characteristics, conidial morphology, and phylogenetic analyses of the internal transcribed spacers, partial translation elongation factor 1-α gene, and partial β-tubulin gene sequence the isolates were identified as Neopestalotiopsis australis. Koch's postulates demonstrated the pathogenicity of N. australis on nanche. This is the first report implicating N. australis as a causal agent of Scab Disease on B. crassifolia in Mexico and in the world.

Resumen:La presencia de contaminantes fotoquímicos en la Cuenca de México es una realidad, y el daño que causan a la salud humana y a la vegetación es evidente. La falta de datos sobre concentraciones de ozono en los bosques de la Cuenca fue la principal razón para realizar el presente estudio en tres áreas boscosas: El Ajusco (AJU), Desierto de los Leones (DDL) e Izta-Popocatépetl (IZP). Se utilizaron monitores pasivos CanOxy Plate TM con períodos de exposición de tres semanas,

Xanthomonas fragariae es el agente causal de la mancha angular de la hoja en el cultivo de fresa (Fragaria × ananassa Duch) en México. El objetivo de este estudio fue caracterizar e identificar las bacterias aisladas basadas en la caracterización fisiológica, bioquímica, morfológica y en pruebas de patogenicidad y genética por PCR. Se aislaron colonias de bacterias con morfología similar a la descrita para X. fragariae a partir de tejido foliar de diferentes genotipos de fresa en Cd. Guzmán, Jalisco, México con síntomas de manchas angulares acuosas en el área adaxial, exudado en nervaduras primarias y secundarias y manchas necróticas. Los resultados de la caracterización de los aislamientos bacterianos los identificaron como X. fragariae, lo cual fue confirmado por el análisis genético con la amplificación del gen hrp y la amplificación y secuenciación del gen 16S rADN. La inoculación de la cepa X. fragariae-22 produjo lesiones angulares y necrosis adyacentes a la nervadura de las hojas en plantas susceptibles de fresa var. Jacona.

In Mexico City, the Canary Island date palm (Phoenix canariensis Chabaud) is an important plant forming part of its landscape identity. In February 2022, pink rot disease symptoms were observed on 16 P. canariensis plants in Mexico City (19°25'43.98"N, 99° 9'49.41"W). The incidence was 27%, while the severity 12%. External symptoms included necrotic lesions that advanced from the petiole towards the rachis. Internal symptoms were rotted, dark brown discoloration in bud, petiole, and rachis. Abundant conidial masses were developed on the infected tissues. Pieces of diseased tissues (5-mm cubes) were surface sterilized for 2 min in 3% sodium hypochlorite, rinsed with sterilized distilled water, plated onto potato dextrose agar (PDA), and incubated at 24°C and 12-h photoperiod, 20 pink fungal colonies were developed with sparse aerial mycelia on PDA. Conidiophores were hyaline, dimorphic, penicillate, and Acremonium-like. Conidia were dimorphic, typically with somewhat truncated ends, 4.5 to 5.7 × 1.9 to 2.3 μm (mean 4.99 × 2.15, n = 100), borne in long chains on penicillate conidiophores; on Acremonium-like conidiophores conidia were cylindrical, straight, and slightly curved, 4.55 to 10.1 × 1.2 to 2.35 μm (mean 8.2 × 1.7, n = 100). These morphological characteristics resembled those of Nalanthamala vermoesenii (Biourge) Schroers (Schroers et al. 2005). Genomic DNA was extracted from the mycelia of a representative isolate CP-SP53. The internal transcribed spacer (ITS) region and the large subunit of ribosomal ribonucleic acid (LSU) were amplified and sequenced. The sequences were deposited in GenBank with accession numbers OQ581472 (ITS) and OQ581465 (LSU). Phylogenetic trees based on ITS and LSU sequences of Nalanthamala species were reconstructed using maximum likelihood and Bayesian inference methods. Isolate CP-SP53 was placed in the clade of Nalanthamala vermoesenii. The pathogenicity test was carried out twice with isolate CP-SP53 on five 3-year-old P. canariensis plants. Four petioles per plant were surface disinfected with 75% ethanol, and wounded with a sterilized scalpel (shallow cuts 0.5 cm wide). A mycelial plug (5 mm in diam.) of a 1-week-old PDA culture was placed on each wounded site. Sterile PDA plugs were used for five non-inoculated control plants. All plants were maintained at 22 ± 2°C and a 12-h photoperiod. Twenty-five days after inoculation (dai), wounded petioles showed the same symptoms observed in the field, whereas control plants remained healthy. Forty-five dai, all inoculated plants died. Pink conidial masses developed on symptomatic tissues. To fulfill Koch’s postulates, the pathogen was reisolated by placing the pink conidial masses onto PDA. The colony characteristics and morphometric measurements were identical to those of isolate CP-SP53. Nalanthamala vermoesenii has been reported on P. canariensis in Greece and United States (Feather et al. 1979; Ligoxigakis et al. 2013) and Syagrus romanzoffiana in Egypt (Mohamed et al. 2016). To our knowledge, this is the first report of Nalanthamala vermoesenii as the causal agent of pink rot on P. canariensis in Mexico. This plant is the most commonly planted ornamental palm in Mexico City. The spread of N. vermoesenii could be a threat for the estimated 15 thousand palms, therefore dramatically change the urban landscape.

No abstract