ABSTRACT: A generalized concept in the Citrus genus is that highly polyembryonic varieties produce only a small number of hybrids. Small zygotic embryos congregate primarily near the micropyle, while nucellar embryos organize near or away from the micropyle. In the present study, the authors determined the number of polyembryonic seeds, embryos per seed, and the largest embryo (LE) position in five citrus cultivars: C35 citrange, Volkamer lemon, Amblycarpa mandarin, Minneola tangelo, and Valencia orange. The percentage of nucellar seedlings obtained exclusively from the LE per seed was then calculated. The polyembryony percentage varied largely between genotypes, from 65 to 98 %, and the mean number of embryos ranged from 2.9 to 4.6. The chalaza contained up to 87 % of the LE. Out of 30 primers, 17 Simple sequence repeats [SSRs] (AG14, ATC09, CAT01, CCSM147, CCSM18, CCSM13, CCSM4, F2, F4, F6, GT03, TAA41, TAA45, TAA1, F7, F11 and TAA52) identified nucellar plants identical to the female parent (genetic similarity index [GSI] value ≥ 0.95). This study establishes for the first time the relationship between the sexual or asexual origin of seedlings derived from LE embryos isolated from seeds and the SSR primers described above. While the five citrus cultivars had high polyembryony levels, 30 % of the resulting plants differed from the female parent in C35 Citrange, 45 % in Volkamer lemon, 15 % in Amblycarpa mandarin, 15 % in Valencia orange, and 45 % in Minneola tangelo. The largest seedling is not always nucellar: in the five citrus species studied, the LE produces 55 to 85 % of the nucellar embryos.

Abstract The degree of substitution of bovine meat for equine meat in different points of sale of the different boroughs of Mexico City was evaluated, and the benefits or similarities with bovine meat as a strong alternative of nutrients were identified. One hundred sixty-one samples of bovine meat were collected, which were subjected to near-infrared reflectance spectroscopy (NIR’s - Food Scan) to determine nutritional composition (moisture content, protein, fat and collagen), meat color (Hunter Lab L*, a* and b*) and polymorphism of repeated sequences to characterize the bovine or equine origin by polymerase chain reaction in agarose gels (PCR). The variables of nutritional composition and meat color were analyzed in a completely randomized design. It was found that nine of the samples were positive for equine meat and 152 samples were positive for bovine meat; resulting in that 5.59 % of bovine meat was replaced by equine meat in the commercialization centers in Mexico City. Likewise, the moisture, protein, fat and collagen content fluctuated between the samples from 73.1 to 75.1 %, from 22.0 to 23.5 %, from 2.0 to 2.3 %, and from 1.3 to 1.4 mg g-1, respectively; observing a slight increase (P<0.05) in the concentration of moisture and protein in bovine meat compared to equine meat. The L* (luminosity) of meat between animal species was different (P<0.05); while in the indicators of meat color a* (from red to green) and b* (from yellow to blue), it fluctuated from 29.80 to 37.50 and 15.00 to 16.20 (P>0.05). It is concluded that the percentage of substitution of bovine meat for equine meat (5.59 %) is considered low and constitutes consumer fraud. However, equine meat has the potential to be a viable alternative for human consumption, as the nutritional composition was similar to bovine meat.

Resumen Se evaluó el grado de sustitución de carne bovina por carne equina en distintos puntos de venta de las diferentes Alcaldías de la Ciudad de México, y se identificó las bondades o similitudes con la carne bovina como una fuerte alternativa de nutrientes. Se colectaron 161 muestras de carne de bovino que fueron sometidas a espectroscopia de reflectancia en el infrarrojo cercano (NIR´s - Food Scan) para determinar composición nutricional (contenido de humedad, proteína, grasa y colágeno), color de la carne (Hunter Lab L*, a* y b*) y polimorfismo de secuencias repetidas para caracterizar el origen bovino o equino por reacción en cadena de la polimerasa en geles de agarosa (PCR). Las variables de composición nutricional y color de la carne se analizaron en un diseño completamente al azar. Se encontró que nueve de las muestras dieron positivas para carne de equino y 152 muestras fueron positivas para carne de bovino; resultando que la carne de bovino fue sustituida el 5.59 % por carne equina en los centros de comercialización en la Ciudad de México. Asimismo, el contenido de humedad, proteína, grasa y colágeno fluctuó entre las muestras de 73.1 a 75.1 %, de 22.0 a 23.5 %, de 2.0 a 2.3 %, y de 1.3 a 1.4 mg g-1, respectivamente; observando un ligero incremento (P<0.05) en la concentración de humedad y proteína en la carne de bovino respecto a la carne equina. La L* (luminosidad) de la carne entre las especies animal fue diferente (P<0.05); mientras que en los indicadores del color de la carne a* (de rojo a verde) y b* (de amarillo a azul) fluctuó de 29.80 a 37.50 y 15.00 a 16.20 (P>0.05). Se concluye que el porcentaje de sustitución de la carne de bovino por carne equina (5.59 %) se considera bajo y constituye un fraude al consumidor. Sin embargo, la carne equina tiene un potencial de ser una alternativa viable para el consumo humano, ya que la composición nutricional fue similar a la carne de bovino.

Abstract: The genomic and transcriptomic analyses for selection and genetic improvement require DNA or RNA of high concentration and purity, coming from different tissues, including semen. The DNA may be from hair, saliva, cartilage, blood, or semen. The methods usually used to extract DNA from semen have low efficiency in terms of quantity and quality. This is due to the solvents and dilutors used for semen conservation, physical and chemical characteristics of sperms, and non-cellular fraction of ejaculate. In this study, modifications to the guanidinium thiocyanate method are proposed, including a second washing of the sample using a phosphate buffer solution, and two washing with organic solvents, one strong (phenol:chloroform:Isoamyl alcohol), and one weak (chloroform:isoamyl alcohol), to get rid of the protein and dilutors present in the sample. Additionally, it is proposed a separate incubation with RNA-ase to reduce contamination of nucleic acids during measurement and dilution preparation for PCR amplification. The precipitation added to the isopropanol of the original method 3 M sodium acetate to separate the residuals of potential PCR inhibitors. Finally, there were included high-speed centrifugation and decantation to avoid the need for mechanical separation of the DNA and protein. The DNA extracted with the modified method did not present degradation, and the quality and quantity were better (P<0.0001) than the original, with a mean of 1.84±0.09 in the range of 260/ 280 and 156.99±7.29 ng/µl for concentration. The present method of extraction is a viable low-cost alternative to obtain DNA from semen with the necessary characteristics for genomic analysis in mammals.

Resumen: Los análisis genómicos y transcriptómicos para selección y mejoramiento genético animal requieren ADN o ARN de alta concentración y pureza, proveniente de diferentes tejidos incluyendo semen. Los métodos usualmente utilizados para extraer ADN de semen son menos efectivos en cantidad y calidad de ADN, debido a los solventes y diluyente utilizados para la conservación, características físico-químicas de los espermatozoides, y fracción no celular del eyaculado. En este estudio, se proponen modificaciones al método de tiocianato de guanidina, incluyendo un segundo lavado de la muestra con solución buffer fosfato, y dos lavados con solventes orgánicos, uno fuerte (fenol:cloroformo:alcohol isoamílico) y uno débil (cloroformo:alcohol isoamílico), para retirar la proteína y diluyente presentes en la muestra. Además, se propone una incubación por separado con ARNasa para reducir contaminación de ácidos nucleicos en la medición y elaboración de diluciones para amplificación por PCR. La precipitación agregó al isopropanol de la metodología original 3 M de acetato de sodio para retirar restos de posibles inhibidores de la PCR. Finalmente, se incluyeron centrifugaciones de alta velocidad y decantaciones para evitar la necesidad de separación mecánica del ADN y la proteína. El ADN extraído con el método propuesto no presentó degradación, y la calidad y cantidad fueron mejores (P<0.0001), encontrándose una media de 1.84±0.09 en el rango 260/280 y 156.99±7.29 ng/µl para la variable de concentración. El presente método de extracción es una alternativa de bajo costo, viable para obtener ADN de semen con características necesarias para análisis genómicos en mamíferos.