The classification of Mexican maize (Zea mays L.) begun since the early 20th century, it was consolidated during the middle of this century, but recent additions and rearrangements have been performed by several authors employing new methods of analysis and collections from diverse origin; nevertheless, maize from the State of Michoacan, Mexico has received little attention in regard to its systematic classification. Maize populations from the Tarasca Mountain Chain in Michoacan are commonly considered in literature, as belonging to the Chalquen˜o race; however, closer observations indicate that significant differences do exist, suggesting the necessity of performing an in-depth study on this respect. Thirty nine native maize populations from the Tarasca Mountain Chain region were evaluated along with 19 typical populations of the Chalquen˜o, Celaya and Conico races coming from the States of Mexico, Puebla, Hidalgo, Quere´taro and Oaxaca. Populations were evaluated in Aranza, Michoacan and Montecillo, Mexico State. Seventeen morphological characters were scored and analyzed by one-way analyses of variance and multivariate techniques. Populations were also genetically analyzed through 17 isozyme loci. Native populations had some alleles not found either in the Chalquen˜o, Celaya or Conico races, and possess larger genetic diversity. Local populations were congregated into a discrete group apart from the typical Chalquen˜o populations, suggesting that landraces from the Tarasca Mountain Chain region might not be considered as belonging to the Chalquen˜o race, but they integrate by themselves a different race.
-The objective of this work was to evaluate the genetic diversity of nine maize races (Zea mays ssp. mays) from Northwestern Mexico and one population of teosinte of the Balsas race (Zea mays ssp. parviglumis). A total of 649 alleles were identified, with an average of 20.9 alleles per locus using 31 microsatellite loci; 84.3% of them were polymorphic loci with a 0.49 expected heterozygosity. Graphic representation of principal coordinate analysis (PCoA) showed broad variation and population distribution. The highest probabilistic value obtained with the ∆K criterion confirmed the existence of five population groups clustered by the Bayesian model. This grouping coincided with the population distribution observed in the PCoA graph. Maize races examined retain broad genetic diversity among and within the evaluated populations.Index terms: Zea mays, conservation strategies, landraces, microsatellites, plant breeding. Diversidade genética e estrutura das raças de milho nativo do Noroeste do MéxicoResumo -O objetivo deste trabalho foi avaliar a diversidade genética de nove raças de milho (Zea mays ssp. mays) do Noroeste do México e uma população de teosinto da raça Balsas (Zea mays ssp. parviglumis). Foram identificados 649 alelos, uma média de 20,9 alelos por locus, utilizando 31 loci microssatélites. Desses, 84,3% eram polimórficos e apresentaram heterozigosidade esperada de 0,49. A representação gráfica da análise de fatores principais (PCoA) mostrou ampla variação e distribuição populacional. O maior valor probabilístico obtido com o critério ΔK confirmou a existência dos cinco grupos populacionais agrupados com o modelo bayesiano. Esse agrupamento coincide com a distribuição populacional observada no gráfico PCoA. As raças de milho examinadas apresentam ampla diversidade genética entre e dentro das populações avaliadas.Termos para indexação: Zea mays, estratégias conservacionistas, raças nativas, microssatélites, melhoramento vegetal.
Determining the sample size in a scientific investigation is important because it gives reliability in the results together with the efficiency in the use of resources and optimization of time. Polyembryony is a characteristic that allows to obtaining clonal and zygotic plants in the same seed. In mango this characteristic is presented, however, there is no information that mentions which is the adequate sample size to evaluate it. The objective of the present work was to determine the optimum sample size by means of the maximum curvature method for future polyembryony studies. Mangoes from the cultivar Manila and Ataulfo were collected from the states of Guerrero and Nayarit, Mexico. In each state, two orchards of each cultivar were chosen, and in each one three trees were selected. In the Fruit Biotechnology laboratory of the Colegio de Postgraduados, Campus Montecillo, five fruit variables were evaluated: weight of fruit, seeds (endocarp and embryos), embryos, weight of the largest embryo and number of embryos. In all the variables evaluated, except for the weight of the largest embryo, the inflection point of the curve was in 6 fruits and an optimal sample size of 8 fruits was determined. The minimum variation coefficients (CV) for fruit weight were from 17.9 to 19.1%, for seed weight 12.7 to 19.3%, embryo weight 12.3 to 17.1% and number of embryos 6.7 to 16.7%. In the case of larger embryo weight, it was determined that 20 fruits are the optimal sample size, obtaining CV from 7 to 22.6%. The fruit and seed weight characteristics were the least variation, and number of embryos with higher CV. The cultivar Manila of Nayarit presented the highest CV in all the variables studied.
El piñón mexicano, Jatropha curcas L. (Euphorbiaceae), es utilizada para diferentes propósitos: alimento, medicina, tutor, sombra y biocombustibles. No obstante la creciente importancia de la especie a nivel mundial, aún se carece de información precisa pertinente a su propagación. Teniendo como objetivo evaluar experimentalmente: 1) la germinación; 2) emergencia-tiempo y porcentaje-; 3) liberación de hojas cotiledonares; y 4) el porte de plántulas a diez días después de siembra (DDS). Se utilizaron semillas de seis accesiones, provenientes de seis estratos de elevación (191, 347, 542, 545, 610 y 630 msnm), en tres niveles de temperatura (25, 30 y 35 °C) y dos condiciones de testa (con y sin). A 30 °C la germinación se presentó en 3.8 días, en la accesión A-630 msnm la germinación, emergencia y liberación de hojas fue rápida (3.6, 4.6 y 7.4 días), mientras que el mayor porcentaje en las variables indicadas se presentó en A-347 (97.7, 96.3, 95.5%) y las plántulas de mayor porte (16.7 cm), también de A-630, comparado con los otros niveles de temperatura y accesiones colectadas en otras elevaciones. En relación con la testa, la germinación, emergencia y liberación de las hojas ocurrió más rápido cuando se eliminó ésta (3.8, 5.5 y 7.8 días); sin embargo, el mayor porcentaje de germinación se observó en las semillas con testa (88.5%). Los resultados aportan información útil en la definición de la tecnología conducente al perfeccionamiento de los criterios agronómicos para su cultivo eficiente.
El presente trabajo tuvo como objetivo estudiar las variaciones relacionadas con la gran sequía invernal (GSI), la sequía intraestival (SI), la ocurrencia de heladas, golpes de calor y excesos de lluvia, aprovechando datos históricos disponibles de la localidad de Tamazula, Jalisco como un espacio dentro de un nicho; así mismo, comparar las variaciones antes y después de 1975, año tomado como referencia de la manifestación del último cambio climático según la Figura 2. Otro objetivo colateral fue vincular dicho desarrollo histórico con un experimento de variedades de caña realizado en 2011-2013 cerca de Tamazula, Jalisco.Rev. iberoam. bioecon. cambio clim. Vol.1(1) 2015; 185-206
El huanglongbing (HLB) es la enfermedad más devastadora de los cítricos a nivel mundial y está presente en el estado de Colima desde 2010, zona productora de limón mexicano (Citrus aurantifolia). Esta enfermedad causa un desequilibrio en el reparto de carbohidratos e inhibe la fotosíntesis. También afecta la concentración de nutrientes en hoja. El objetivo de este trabajo fue determinar los cambios fisiológicos en árboles en producción de limón mexicano infectados con HLB. El estudio se desarrolló en Colima en 2017. Se determinó la concentración de almidón, sacarosa y glucosa en nervadura central y lámina de hojas de diferentes edades (120 y 30 días) y almidón en raíces. La concentración de clorofilas por método analítico e índice SPAD en hojas con diferentes niveles de síntomas de HLB y análisis foliares de nutrientes minerales. Las hojas con HLB tuvieron mayor concentración de almidón en la lámina de 120 días. La sacarosa se concentró en las nervaduras de hojas de 120 días. Mientras que la glucosa se incrementó en las nervaduras de 30 y 120 días. Las raíces de árboles infectados con HLB mostraron 40% menor concentración de almidón comparados con árboles sanos. Disminución en el contenido de clorofilas e índice SPAD en función del grado de afectación. Así como menor concentración de K, Ca, Mg, Cu, Fe, Zn y B. El conocer los cambios que ocasiona el HLB en limón mexicano permitirá desarrollar prácticas que disminuyan su impacto.
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