Abstract Influenza is a costly disease for the population. It is a cause of seasonal morbidity and mortality, epidemics and pandemics or syndemics. Given the variability of the virus, surveillance systems are implemented in order to update the strains and include them in the annual influenza vaccine. This vaccine is currently recommended in some high-risk groups. However, universal vaccination remains controversial. Objective: To evaluate the evidence and describe the position of a panel of experts on the relevance of universal vaccination against influenza virus. Material and methods: Five clinical questions were asked, whereby a systematic search of the literature in electronic sources and a Delphi panel was carried out. The evidence was analyzed and recommendations were issued by the experts. Results: The group of experts recommends vaccinating the population starting at six months of age include people who live with egg protein allergy; with comorbidities (diabetes, obesity, cancer) health workers and pregnant women. Conclusions: Vaccination, starting with vulnerable groups, is a necessary, ethical and cost-effective strategy. However, extending coverage to achieve universal vaccination could reduce the transmission of the disease and its consequences in the population.

Resumen La influenza es una enfermedad costosa para la población. Es causa de morbimortalidad estacional, epidemias y pandemias o sindemias. Debido a la variabilidad del virus, se implementan sistemas de vigilancia para actualizar las cepas e incluirlas en la vacuna antiinfluenza anual. Actualmente se recomienda esta vacuna en algunos grupos de alto riesgo. Sin embargo, la vacunación universal es aún controvertida. Objetivo: Evaluar la evidencia y describir la posición de un panel de expertos sobre la pertinencia de la vacunación universal contra el virus de influenza. Material y métodos: Se realizaron cinco preguntas clínicas, con las que se realizó una búsqueda sistemática de la literatura en fuentes electrónicas y un panel Delphi. Se analizó la evidencia y se emitieron recomendaciones por los expertos. Resultados: El grupo de expertos recomienda vacunar a la población desde los seis meses de edad e incluir a personas que viven con alergia a la proteína del huevo, con comorbilidades (diabetes, obesidad, cáncer), trabajadores de la salud y embarazadas. Conclusiones: La vacunación, iniciando con los grupos vulnerables, es una estrategia necesaria, ética y costo-efectiva. Sin embargo, extender la cobertura para lograr la vacunación universal podría disminuir la transmisión de la enfermedad y sus consecuencias en la población.

Resumen Objetivo: determinar las características de los usuarios y servicios basados en el triaje. Método: estudio observacional descriptivo que incluyó pacientes que acudieron al servicio de urgencias y se les realizó triaje en dos instituciones de alto nivel de complejidad en Medellín en el año de 2018. Resultado: se incluyeron 4159 pacientes. La mediana de edad fue de 38 años, el 54,61 % eran de sexo masculino. El 85,54 % habitaban en el área metropolitana y el 67,78 % eran del régimen contributivo. En cuanto al mes con mayor afluencia de pacientes fue mayo con un 10,55 % seguido del mes de enero con 10,29 %; y el día de la semana fue el martes con 16,15 %, siendo el horario más frecuente entre las 9:00 y 12:00 del día con 18,32 %. Conclusión: una adecuada caracterización del paciente en urgencias por medio del triaje es útil para una atención oportuna y lograr la optimización de los servicios.

Abstract Objective: determine the characteristics of users and services based on triage. Method: descriptive observational study, which included patients who attended the emergency department and where classified with triage in two institutions of a high level of complexity in Medellín in the year 2018. Result: 4159 patients were included. The median age was 38 years, 54,61 % were male. 85,54 % lived in the metropolitan area and 67,78 % were from the contributory regime. Regarding the month with the highest influx of patients, it was May with 10,55 % followed by the month of January with 10,29 %; and the day of the week was Tuesday with 16,15 %, being the most frequent time between 9:00 and 12:00 of the day with 18,32 %. Conclusion: An adequate characterization of the patient in the emergency room through triage is useful for timely care and optimization of services.

Resumo Objetivo: determinar as características dos usuários e dos serviços baseados na triagem. Métodos: estudo observacional descritivo, que incluiu pacientes que acudiram no serviço de urgências e lhes fizeram triagem em duas instituições de alto nível de complexidade em Medellín no ano 2018. Resultados: 4159 pacientes foram incluídos. A mediana de idade foi 38 anos, o 54,61 % foram do sexo masculino. O 85,54 % moravam na área metropolitana e o 67,78 % foram do regime contributivo. Enquanto ao mês de maior afluência de pacientes foi maio com 10,55 % seguido do mês de janeiro com 10,29 %; e o dia da semana foi a terça-feira com 16,15 %, sendo o horário mais frequentado entre as 9h00 e as 12h00 da manhã com 18,32 %. Conclusão: uma adequada caracterização do paciente nas urgências por médio da triagem é útil para ter uma atenção médica oportuna e lograr a optimização dos serviços.

Abstract: This work analyzes the experience of an accompaniment practices program based in a sociocultural perspective of academic literacy and its effects in the formative trajectory of first-year higher education students. Accompaniment experience is articulated with biographical narrative research and pedagogical tact, writers record the conscious becoming of two students in the training process around academic writing linked to specific fields of knowledge. The work is based on a qualitative perspective, methodologically exposes the intervention and writing strategies in accompaniment practices to document formative trajectories that empower students as active agents around language (orality, reading and writing) in higher education. Finally, authors present some reflections around the role of institutional accompaniment conditions to transform students in authors or their own words.

Resumen: Este trabajo analiza la experiencia de una propuesta de prácticas de acompañamiento, fundamentada en una perspectiva sociocultural de literacidad académica, que impacta en la trayectoria formativa de estudiantes de primer año de educación superior. La experiencia se articula en la perspectiva biográfico-narrativa y la pedagogía del tacto. Los autores documentan el devenir consciente de dos alumnos en el proceso de formación alrededor de la escritura académica, ligada a campos de conocimiento concretos. Metodológicamente, se expone cómo, desde una perspectiva cualitativa, se organizan las estrategias de intervención y documentación del proceso de la experiencia en la construcción de trayectorias de formación que hacen de los estudiantes agentes activos y empoderados alrededor del lenguaje (oralidad, lectura y escritura) en el nivel universitario. El texto finaliza con reflexiones sobre el papel de las condiciones institucionales de acompañamiento para que los alumnos se conviertan en autores de su palabra.

ABSTRACT Zanthoxylum pseudodumosum is an endemic aromatic plant from Cuba that has been little studied, for this reason the aim of this work was to determinate the chemical composition of different products prepared from it, as well as to evaluate the antifungal activity in vitro against A. solani. The essential oil was obtained from its leaves by hydrodistillation, as well as the hexane and hydroalcoholic extracts by maceration. The phytochemical characterization of the isolated fractions was performed by chemical tests and with the help of thin layer chromatography. The products obtained were tested against the phytopathogenic fungus Alternaria solani, obtaining the Minimum Inhibitory Concentration (MIC) values by the microdilution method. The main metabolites found were terpenes, alkaloids, coumarins, anthraquinones, steroids and phenolic compounds. Hexane extract showed good antifungal activity with a MIC value of 1000 μgml-1, followed by essential oil with 2000 μgml-1.

RESUMEN Zanthoxylum pseudodumosum es una planta aromática endémica de Cuba que ha sido poco estudiada, por lo que el objetivo de este trabajo fue determinar la composición química de diferentes productos preparados a partir de la misma, así como evaluar la actividad antifúngica “in vitro” frente a A. solani. De sus hojas se obtuvo el aceite esencial mediante hidrodestilación, así como los extractos hexánico e hidroalcohólico mediante maceración. Se realizó la caracterización fitoquímica de las fracciones aisladas mediante ensayos químicos y con ayuda de la cromatografía de capa delgada. Los productos obtenidos se ensayaron frente al hongo fitopatógeno Alternaria solani, obteniendo los valores de Concentración Mínima Inhibitoria (CMI) mediante el método de microdilución. Los principales metabolitos encontrados fueron terpenos, alcaloides, cumarinas, antraquinonas, esteroides y compuestos fenólicos. El extracto hexánico mostró buena actividad antifúngica con un valor de CMI de 1000 μgmL-1, seguido del aceite esencial con 2000 μgmL-1.

Abstract: As part of the Curricular Processes and Accompanying Practices research project, we show how, in search for good practices in the educational field, a primary school teacher undertakes the task of trying to implement the educational policies of increasing the quality of education. We adopt the biographical-narrative approach to produce knowledge about the subjects and their practices, as well as the knowledge they generate in the performance of their work. In this text, we show both part of teacher’s journey and instances of the experimentation of pedagogical ideas in the classroom, in order to highlight the tension faced by elementary teachers to manage and circulate pedagogical ideas in daily life when they adopt in their classroom the project-based method to generate innovative educational processes. We describe how concrete individuals carry with them pedagogical ideals that must face a complex network of relationships in which teachers try, day by day, with the development of materials, tensions with parents, principals and educational regulations, to do quality work in a city school that affects the training processes and teaching practices. We close the text with some reflections on the management of innovative projects in basic education in the current educational context.

Resumen: Como parte del proyecto de investigación “Procesos curriculares y prácticas de acompañamiento” mostramos cómo, en la búsqueda de realizar buenas prácticas en el ámbito educativo, una maestra de primaria enfrenta su labor al tratar de asumir las políticas educativas de elevar la calidad de la educación. Nos incorporamos a la perspectiva biográfico-narrativa para producir saber sobre los sujetos y sus prácticas y el saber que generan en la realización de su labor. En este texto mostramos tanto parte de la trayectoria de ser docente como escenas de la experimentación de ideas pedagógicas en el aula, con el propósito de evidenciar la tensión de los maestros de primaria para gestionar y circular ideas pedagógicas en la vida cotidiana, al asumir en su salón de clases el método de proyectos y con ello generar procesos educativos innovadores. Damos cuenta de cómo los sujetos concretos son portadores de ideales pedagógicos que se enfrentan a la compleja red de relaciones sobre la cual los docentes intentan día a día, con la elaboración de materiales, entre tensiones con padres, directivos y la normatividad educativa vigente, hacer un trabajo de calidad en una escuela citadina que incide en los procesos de formación y las prácticas docentes. Finalizamos el texto con algunas reflexiones sobre la gestión de proyectos innovadores en educación básica en el contexto educativo actual.

Abstract INTRODUCTION: Biomarkers are critical tools for finding new approaches for controlling the spread of tuberculosis (TB), including for predicting the development of TB therapeutics, vaccines, and diagnostic tools. METHODS: Expression of immune biomarkers was analyzed in peripheral blood cells stimulated and non-stimulated with M. tuberculosis antigens ESAT-6, CFP10 and TB7.7. in Warao indigenous individuals. These biomarkers may be able to differentiate TB states, such as active tuberculosis (ATB) cases and latent tuberculosis infection (LTBI) from non-infected controls (NIC). A real-time reverse transcription polymerase chain reaction (RT-qPCR) assay was performed on 100 blood samples under non-stimulation or direct ex vivo conditions (NS=50) and stimulation conditions (S=50). RESULTS: The findings are shown as the median and interquartile range (IQR) of relative gene expression levels of IFN-γ, CD14, MMP9, CCR5, CCL11, CXCL9/MIG, and uPAR/PLAUR immune biomarkers. MMP9 levels were significantly higher in the LTBI-NS and LTBI-S groups compared with the NIC-NS and NIC-S groups. However, CCR5 levels were significantly lower in the LTBI-S group compared with both NIC-NS and NIC-S groups. CCL11 levels were significantly lower in the LTBI-S group compared with the NIC-NS group. CONCLUSIONS: Preliminary findings showed that MMP9 immune biomarkers separated LTBI indigenous individuals from NIC indigenous individuals, while CCR5, CCL11, CD14, and IFN-γ did not differentiate TB states from NIC. MMP9 may be useful as a potential biomarker for LTBI and new infected case detection among Warao indigenous individuals at high risk of developing the disease. It may also be used to halt the epidemic, which will require further validation in larger studies.

BACKGROUND Once in the pulmonary alveoli, Mycobacterium tuberculosis (Mtb) enters into contact with alveolar macrophages and dendritic cells (DCs). DCs represent the link between the innate and adaptive immune system owing to their capacity to be both a sentinel and an orchestrator of the antigen-specific immune responses against Mtb. The effect that the virulence of Mtb has on the interaction between the bacilli and human DCs has not been fully explored. OBJECTIVE To evaluate the effect of Mtb virulence on human monocyte-derived DCs. METHODS We exposed human monocyte-derived DCs to Mtb clinical strains (isolated from an epidemiological Mtb diversity study in Mexico) bearing different degrees of virulence and evaluated the capacity of DCs to internalise the bacilli, control intracellular growth, engage cell death pathways, express markers for activation and antigen presentation, and expand to stimulate autologous CD4+ T cells proliferation. FINDINGS In the case of the hypervirulent Mtb strain (Phenotype 1, strain 9005186, lineage 3), we report that DCs internalise and neutralise intracellular growth of the bacilli, undergo low rates of apoptosis, and contribute poorly to T-cell expansion, as compared to the H37Rv reference strain. In the case of the hypovirulent Mtb strain (Phenotype 4, strain 9985449, lineage 4), although DCs internalise and preclude proliferation of the bacilli, the DCs also display a high level of apoptosis, massive levels of apoptosis that prevent them from maintaining autologous CD4+ T cells in a co-culture system, as compared to H37Rv. MAIN CONCLUSIONS Our findings suggest that variability in virulence among Mtb clinical strains affects the capacity of DCs to respond to pathogenic challenge and mount an immune response against it, highlighting important parallels to studies previously done in mouse models.

Abstract: Objective: To identify and characterize Aedes aegypti’s AAEL006536 gene proximal upstream cis-regulatory sequences activated by dengue virus infection. Materials and methods: A. aegypti Rockefeller strain mosquitoes were blood fed or infected with dengue virus 2. Open chromatin profiling was then carried out in pools of midguts from each group of mosquitoes. Results: The proximal upstream region does not contain open chromatin sites in the midguts of blood-fed mosquitoes as detected by FAIRE-qPCR. In contrast, two cis-regulatory sites were identified in the same upstream region of dengue virus-infected mosquito midguts. The distal sequence contains STAT-, REL- and C/EBP-type transcription factor binding sites. Conclusion: The activation of two proximal cis-regulatory sequences, induced by dengue virus infection, is mediated by chromatin remodeling mechanisms. Binding sites suggest a dengue virus infection-induced participation of immunity transcription factors in the up-regulation of this gene. This suggests the participation of the AAEL006536 gene in the mosquito’s antiviral innate immune response.

Resumen: Objetivo: Identificar y caracterizar las secuencias reguladoras activadas por la infección por virus dengue en la región proximal del gen AAEL006536 de Aedes aegypti. Material y métodos: Mosquitos de la cepa Rockefeller de A. aegypti se infectaron con virus dengue o se alimentaron con sangre. Se obtuvieron los perfiles de cromatina abierta del locus en los intestinos de cada uno de los grupos. Resultados: Se identificaron dos sitios reguladores solo en los intestinos de mosquitos infectados por virus dengue. El sitio distal contiene sitios de unión a factores de transcripción tipo REL, STAT y C/EBP. Conclusiones: La activación de dos sitios reguladores proximales está mediada por la remodelación de la cromatina. Los sitios de unión a factores de transcripción en el sitio regulador distal sugieren la participación de las vías de inmunidad en la regulación del gen. Esto sugiere la participación de este gen en la respuesta inmune del mosquito frente a la infección viral.

Abstract: Objective: To identify and characterize Aedes aegypti’s AAEL006536 gene proximal upstream cis-regulatory sequences activated by dengue virus infection. Materials and methods: A. aegypti Rockefeller strain mosquitoes were blood fed or infected with dengue virus 2. Open chromatin profiling was then carried out in pools of midguts from each group of mosquitoes. Results: The proximal upstream region does not contain open chromatin sites in the midguts of blood-fed mosquitoes as detected by FAIRE-qPCR. In contrast, two cis-regulatory sites were identified in the same upstream region of dengue virus-infected mosquito midguts. The distal sequence contains STAT-, REL- and C/EBP-type transcription factor binding sites. Conclusion: The activation of two proximal cis-regulatory sequences, induced by dengue virus infection, is mediated by chromatin remodeling mechanisms. Binding sites suggest a dengue virus infection-induced participation of immunity transcription factors in the up-regulation of this gene. This suggests the participation of the AAEL006536 gene in the mosquito’s antiviral innate immune response.

Resumen: Objetivo: Identificar y caracterizar las secuencias reguladoras activadas por la infección por virus dengue en la región proximal del gen AAEL006536 de Aedes aegypti. Material y métodos: Mosquitos de la cepa Rockefeller de A. aegypti se infectaron con virus dengue o se alimentaron con sangre. Se obtuvieron los perfiles de cromatina abierta del locus en los intestinos de cada uno de los grupos. Resultados: Se identificaron dos sitios reguladores solo en los intestinos de mosquitos infectados por virus dengue. El sitio distal contiene sitios de unión a factores de transcripción tipo REL, STAT y C/EBP. Conclusiones: La activación de dos sitios reguladores proximales está mediada por la remodelación de la cromatina. Los sitios de unión a factores de transcripción en el sitio regulador distal sugieren la participación de las vías de inmunidad en la regulación del gen. Esto sugiere la participación de este gen en la respuesta inmune del mosquito frente a la infección viral.

BACKGROUND Type 2 diabetes (T2D) is a risk factor for the development of tuberculosis (TB), although the associated mechanisms are not known. OBJECTIVES To study the association between T2D and the basal phenotype of macrophages, and their immune response to Mycobacterium tuberculosis (Mtb) infection. METHODS We evaluated the influence of T2D on the response of monocyte-derived macrophages (MDM) to Mtb in patients with T2D (n = 10) compared to healthy subjects (n = 9), before and after infection with Mtb clinical isolates bearing different degrees of virulence. The levels of cell surface markers for activation secreted cytokines and chemokines, bacterial association, and intracellular bacterial growth were evaluated. FINDINGS The expression levels of HLA-DR, CD80, and CD86 were low while those of of PD-L1 were high in uninfected MDMs derived from patients with diabetes; as a result of Mtb infection, changes were only observed in the expression levels of PD-L1. The levels of cytokines (e.g., IL-6, IL-1β, IL-10, and IL-12) and chemokines (e.g., MCP-1, MIG, and RANTES) are perturbed in MDMs derived from patients with diabetes, both before infection and in response to Mtb infection. In response to the more virulent Mtb strains, the levels of association and bacterial clearance were diminished in MDMs derived from patients with diabetes. CONCLUSIONS T2D affects the basal activation state of the macrophages and its capacity to respond and control Mtb infection.

This article outlines the production of autobiographical texts in education during the last decade in Mexico. We have divided the paper into two sections. In the first section, based on the idea of field, we show the referents that have been valuable for us in approaching the biographical/educational field in Mexico, and the way biographies are disseminated in Mexican culture. The second section centers on areas or interests in the biographical field, organized as three topics of broad interest for the academic community: biography/autobiography; oral histories/stories/life histories and trajectory. The article concludes with some reflections: the diversification of autobiographies; reflection on experience and theory; the issue of truth in the biographical field; traditions regarding the utilization of sacred authors and the author's word in autobiographical research.

El artículo traza la producción de textos en torno a lo autobiográfico en educación durante la última década en México. Hemos organizado el trabajo en dos secciones. En la primera mostramos, bajo la idea de campo, los referentes que nos han sido valiosos para aproximarnos al campo biográfico-educativo en México y la forma como lo biográfico está diseminado en la cultura mexicana. La segunda se centra en los ejes, temáticas o intereses del campo biográfico desplegado en tres temas de amplio interés para la comunidad académica: biografía/autobiografía; historia oral/relatos/historias de vida y trayectoria. El artículo concluye con algunas reflexiones: la diversificación de lo autobiográfico; la reflexión sobre la experiencia vivida y la teoría al uso; el asunto de la verdad en el campo biográfico; las tradiciones sobre la utilización de los autores consagrados y la palabra del autor en las indagaciones autobiográficas.

Objectives:To determine the prevalence of HPV and the risky sexual behaviors associated to it in a sample of male college students, taking into account genotype and viral load.Methods:From 2002 to 2003, male students from the Autonomous University of Morelos State completed a questionnaire and provided self-collected genital samples to detect and quantify HPV. We performed a bivariate and a multivariate logistic regression analysis to identify correlates associated with the infection and to assess the viral load as a function of the viral infecting type. The fragments of β-globin gene and L1 of HPV, were amplified, purified and cloned, to evaluate viral load.Results:Among 253 subjects, HPV prevalence was 19.4%, and HPV16 was the most common subtype. History of STIs (OR = 4.8; 95% CI 1.2–18.9), contraceptive pill use by female partner (OR = 2.6; 95% CI 1.1–6.3) and exchanging sex for money (OR = 4.9; 95% CI 1.2–20) were associated to the HPV infection. HPV16 viral load was 7.8 copies (HPV/beta-globin) compared to 0.9 copies for other HPV types.Discussion:HPV16 displayed the highest viral load, and it was the most prevalent. It was found that using contraceptive pills by female partners was associated with HPV infection.

The research was conducted from 2009-2011 in the Business Unit Base of Various Productions Guantanamo (UEB-PROVARI) in order to determine the optimal dose of Pectimorf® for rooting from cuttings of guava Cuban Red Dwarf. The cuttings were subjected to immersion in each of six solutions: 1) 5 mg / L of IAA, 2) distilled water, four doses of Pectimorf®, 3) 10, 4) 20, 5) 30 and 6) 40 mg L-1; after 60 days were evaluated: survival (%), number of roots, fresh and dry root biomass (g), root fraction and radical efficiency index (%). The experiment was conducted as a completely randomized design, with a sample of 10 cuttings per treatment. Data was subjected to analysis of variance and means were compared by Duncan's multi range test (p ≤ 0.05). An F Test was performed to compare the responses on cuttings under AIA and those subjected to water immersion. Responses were compared from cuttings under water and treated only with Pectimorf® doses and for root dry biomass variable was used a simple regression analysis. The results showed that the cuttings to which AIA was applied, had better rooting response than those were Pectimorf® was applied, but the latter in any dose studied was able to induce adventitious root formation in the cuttings and the best response of rooting occurred in cuttings were applied 20 mg L-1 of Pectimorf®.

La investigación se desarrolló de 2009 a 2011 en la Unidad Empresarial de Base de Producciones Varias de Guantánamo (UEB-PROVARI) con el objetivo de determinar la dosis óptima de PectiMorf® para el enraizamiento de esquejes de guayaba Enana Roja Cubana. Los esquejes se sometieron a inmersión en una de seis soluciones: 1) 5 mg/L de AIA, 2) agua destilada; cuatro dosis de PectiMorf®, 3) 10, 4) 20, 5) 30 y 6) 40 mg L-1. Transcurridos 60 días se evaluó: supervivencia (%), número de raíces, biomasa radical fresca y seca (g), fracción radical e índice de eficiencia radical (%). El experimento se realizó según un diseño completamente aleatorizado, teniendo una muestra de 10 esquejes por tratamiento. Los datos se sometieron a análisis de varianza y las medias se compararon mediante la prueba de Rangos Múltiples de Duncan (p ≤ 0.05). Se realizó una prueba de F para comparar las respuestas en estacas sometidas a AIA y las sometidas a inmersión en agua. Se compararon las respuestas de las estacas sometidas a solo agua y las tratadas con las dosis de PectiMorf® y para la variable biomasa seca radical se empleó un análisis de regresión simple. Los resultados mostraron que los esquejes a los que se aplicó AIA tuvieron mejor respuesta de enraizado que aquellos a los que se aplicó PectiMorf®, pero este último en cualquiera de sus dosis estudiadas fue capaz de inducir en los esquejes la formación de raíces adventicias, y la mejor respuesta de enraizamiento ocurrió en los esquejes a los que se aplicó 20 mg L-1de PectiMorf®.

Six corn populations drawn from outstanding forage quality germplasm, and 15 of their direct crosses were assessed in four sites located between 1,117 and 1,932 m asl. The purpose of the present study was to determine general and specific combining ability and mid parent heterosis for whole plant dry matter (TDM), ear dry matter (EDM), stover dry matter (SDM), in vitro dry matter digestibility (IVDMD), neutral detergent fiber content (NDF) and crude protein (CP). Populations showed significant differences for all dry matter yield characteristics, but not for forage quality, while crosses showed differences for EDM and IVDMD. General combining ability effects (GCA) were high and significant only for TDM, while specific combining ability effects (SCA) were significant for IVDMD. Population P3 had the highest GCA for TDM (0.66 t ha-1) and P5F for EDM (0.49 t ha-1). Early cross P1*P2 had the highest heterosis for TDM (17.6 %) and highly significant SCA effects for both TDM and IVDMD (1.48 t ha-1 and 22.6 g kg-1, respectively), while crosses P2*P5F, P1*P4 and P1*P6F had high mid parent heterosis for EDM, with values ranging from 18.6 % to 26.2 %. None of the crosses showed mid parent heterosis for forage traits of importance.

Seis poblaciones de maíz derivadas de fuentes de germoplasma sobresalientes por sus cualidades forrajeras y sus 15 cruzas directas se evaluaron en cuatro localidades entre 1,117 y 1,932 m sobre el nivel del mar. El objetivo fue determinar la aptitud combinatoria general y específica, y la heterosis media para variables de producción: materia seca total (MST), de elote (MSEL) y de rastrojo (MSRAS) y variables de calidad del forraje: digestibilidad in vitro de la materia seca (DIVMS), contenido de fibra detergente neutro (FDN) y proteína cruda (PC). Las poblaciones difirieron significativamente en las tres variables de producción, pero no en calidad forrajera; en cambio las cruzas difirieron en producción de MSEL y en DIVMS. Los efectos de aptitud combinatoria general (ACG) fueron significativos sólo para MST y MSEL; mientras que los efectos de aptitud combinatoria específica (ACE), lo fueron adicionalmente para DIVMS. La población P3 tuvo la mayor ACG para MST (0.66 t ha-1), y la población P5F para MSEL (0.49 t ha-1). La cruza precoz P1xP2 presentó la heterosis media más alta para MST con 17.6 % y efectos positivos y significativos de ACE para MST y DIVMS con valores de 1.48 t ha-1 y 22.6 g kg-1. En cambio, las cruzas P2xP5F, P1xP4 y P1xP6F tuvieron los valores de heterosis más altos para MSEL con valores de 18.1 a 26.2 %. Ninguna cruza tuvo heterosis media importante para caracteres de calidad de forraje.