RESUMO
Mexico, as the center of origin of avocado (Persea americama Mill.), harbors a wide genetic diversity of this species, whose identification may provide the grounds to not only understand its unique population structure and domestication history, but also inform the efforts aimed at its conservation. Although molecular characterization of cultivated avocado germplasm has been studied by several research groups, this had not been the case in Mexico. In order to elucidate the genetic structure of avocado in Mexico and the sustainable use of its genetic resources, 318 avocado accessions conserved in the germplasm collection in the National Avocado Genebank were analyzed using 28 markers [9 expressed sequence tag-Simple Sequence Repeats (SSRs) and 19 genomic SSRs]. Deviation from Hardy Weinberg Equilibrium and high inter-locus linkage disequilibrium were observed especially in drymifolia, and guatemalensis. Total averages of the observed and expected heterozygosity were 0.59 and 0.75, respectively. Although clear genetic differentiation was not observed among 3 botanical races: americana, drymifolia, and guatemalensis, the analyzed Mexican population can be classified into two groups that correspond to two different ecological regions. We developed a core-collection by K-means clustering method. The selected 36 individuals as core-collection successfully represented more than 80% of total alleles and showed heterozygosity values equal to or higher than those of the original collection, despite its constituting slightly more than 10% of the latter. Accessions selected as members of the core collection have now become candidates to be introduced in cryopreservation implying a minimum loss of genetic diversity and a back-up for existing field collections of such important genetic resources.
RESUMO
Antecedentes: La malnutrición es un problema tanto en países desarrollados como en desarrollo, y en Latinoamérica, una opción viable es reconsiderar las dietas precolombinas tradicionales basadas en las especies endémicas. En Mesoamérica el chile o chilli (Capsicum annuum L.) desempeñó una función esencial, y perdura en la gastronomía mexicana. Objetivo: evaluar la variación entre y dentro de cinco morfotipos de chile (C. annuum L.) nativo de Oaxaca, México, en relación al contenido de minerales en fruto. Métodos: Una colección de 45 muestras poblacionales de chile, agrupadas en cinco morfotipos, nominados como chile de Agua, Tabiche, Piquín, Solterito y Nanche, fueron sembradas en invernadero bajo un diseño de bloques al azar con tres repeticiones. A la cosecha se obtuvo una muestra de 300 a 500 g de frutos por población, a partir de la que se obtuvieron cenizas solubilizadas en medio ácido, y la determinación de Cu, Fe, Mg, Zn, Na, K, y Ca se hizo por espectrofotometría de absorción atómica, y S y P se cuantificó mediante un espectrofotómetro UV-visible. Resultados: En el análisis de varianza se determinaron diferencias significativas (P < 0,05) entre y dentro de morfotipos de C. annuum para todos los macro y microelementos evaluados. Solterito sobresalió en ocho elementos minerales, le siguen Piquín y de Agua. En contenido de Fe sobresalieron Piquín y Solterito con 8,0 y 8,5 mg/100 g de pesos seco de muestra. Dentro de cada morfotipo sobresalen diferentes poblaciones: CAG03 y CAG10 en chile de Agua; CNA02 de Nanche; CPI02 y CPI09 de Piquín; CSO01, CSO02 y CSO03 de Solterito; y CTA02 y CTA05 del tipo Tabiche. Las diferencias entre morfotipos se confirmaron mediante un análisis discriminante múltiple y las distancias de Mahalanobis. Conclusiones: Los resultados muestran diferencias entre y dentro de morfotipos de C. annuum, y los valores del contenido de minerales reportados muestran que, el chile es un alimento con alto valor nutricional porque 100 g de peso seco potencialmente pueden suplir las necesidad diarias de Cu, Mg, P, y una proporción importante de Fe, Zn y K, entre otros elementos.
Background: Malnutrition is a major health problem in developed and developing countries, and in Latino American, a viable option is reconsider the pre-Columbian and traditional diets based on endemic species. In Mesoamerica, the chilli or pepper (Capsicum annuum L.) played an important role, and its contribution remain until today in the Mexican gastronomy. Objective: the aim of the present work was to evaluate the variation among and within five morphotypes of pepper (C. annuum L.) native of Oaxaca, Mexico, in relation to minerals content in fruits. Methods: a collection of 45 population samples of chilli pepper, which were grouped in five morphotypes named as chile de Agua, Tabiche, Piquin, Solterito and Nanche, and later planted in greenhouse conditions under a complete blocks randomized design with three replications. At harvest time a fruit samples from 300 to 500 g per population were obtained, and later the samples were incinerated to obtain ashes, which were solubilized in acid medium. The determinations of Cu, Fe, Mg, Zn, Na, K, and Ca were done by atomic absorption spectrometry, and the S and P elements were quantified by an UV-vis spectrometer. Results: in the analysis of variance, significant differences (P < 0.05) were determined among and within morphotypes of C. annuum over all macro and trace elements. Solterito presented the highest values in eight mineral elements, after Piquin and chile de Agua were the second more important. In Fe content, Piquin and Solterito showed high values between 8.0 and 8.5 mg/100 g of dry sample weight. Into each morphotype, the outstanding populations were: CAG03 and CAG10 from chile de Agua; CNA02 of Nanche; CPI02 and CPI09 of Piquin type; CSO01, CSO02 and CSO03 from Solterito; and CTA02 and CTA05 from Tabiche type. The differences among morphotypes were confirmed in the multiple discriminant analysis and the Mahalanobis' distances. Conclusions: The results showed differences among and within morfotypes of C. annuum, and the minerals content reported indicate that, the chilli pepper is a food with high nutritional values. In fact 100 g of dry weight, potentially can supply the dairy needs of Cu, Mg, P and an important proportion of the needs of Fe, Zn and K, among other nutritional elements.
