[en] Onions are the second most-valuable vegetable in the world. Despite its global culinary and economic significance, the knowledge of genetic diversity and resources is limited. The aim of this study was to morphologically and physico-chemically characterize eighty-six onion landraces from Spain, part of the secondary Mediterranean Centre of diversity. The evaluated traits in the bulb included: weight, shape, firmness, soluble solids content (SSC), pungency and sugars content (glucose, fructose and sucrose). The results evidenced a great variability in all the evaluated traits. Correlations were significant between pungency and SSC (r = 0.34), firmness (r = 0.32), and sucrose content (r = 0.34); between fructose and glucose contents (r = 0.79); between sucrose content and SSC (r = 0.57); between SSC and weight (r = –0.35); between fructose and sucrose contents (r = –0.22); and between weight and sucrose content (r = –0.43). the combination of cluster and discriminant analyses resulted in a classification into four clusters (95.3% fit). Cluster 1 is represented by firm, pungent and large-sized bulbs; cluster 2 consists of large-sized, mild and sweet onions; cluster 3 is constituted by pungent, high-SSC and small-sized bulbs and cluster 4 is made up by elongated bulbs. The variability in important agronomical traits found point out that these onion accessions could be candidates for future breeding programs. In addition, the clustering could make the initial plant material selection easier and the correlations among the evaluated traits found could help to establish adequate selection strategies.

[es] La cebolla es el segundo cultivo hort&iacute;cola a nivel mundial. Sin embargo, el conocimiento sobre los recursos y la diversidad gen&eacute;tica de esta especie es limitado. Por ello, el objetivo del presente trabajo consisti&oacute; en el estudio morfol&oacute;gico y f&iacute;sico-qu&iacute;mico de una colecci&oacute;n de 86 cultivares de cebolla procedentes de Espa&ntilde;a (que forma parte del centro secundario de diversificaci&oacute;n). Los caracteres evaluados en el bulbo incluyeron: peso, forma, firmeza, contenido en s&oacute;lidos solubles (SSC), pungencia y contenido en az&uacute;cares (glucosa, fructosa y sacarosa). Los resultados evidenciaron una gran variabilidad en todos los caracteres evaluados. Las correlaciones fueron significativas entre la pungencia y SSC (r = 0,34), firmeza (r = 0,32) y contenido en sacarosa (r = 0,34); entre contenido en fructosa y glucosa (r = 0,79); entre contenido en sacarosa y SSC (r = 0,57); entre SSC y peso (r = &ndash;0,35); entre contenido en fructosa y sacarosa (r = &ndash;0,22) y entre el peso y contenido en sacarosa (r = &ndash;0,43). El an&aacute;lisis discriminante dio lugar a la formaci&oacute;n de cuatro grupos con un ajuste del 95,3%. El grupo 1 est&aacute; formado por bulbos grandes, firmes y picantes, el grupo 2 por cebollas grandes, suaves y dulces, el grupo 3 por cebollas peque&ntilde;as, picantes y con un alto SSC y el grupo 4 por bulbos de forma alargada. La variabilidad encontrada para caracteres de inter&eacute;s agron&oacute;mico indica que este material podr&iacute;a ser utilizado en futuros programas de mejora gen&eacute;tica de esta especie. Adem&aacute;s, la agrupaci&oacute;n de los cultivares contribuir&iacute;a a localizar mejor el material vegetal de inter&eacute;s y las correlaciones halladas entre los caracteres evaluados a establecer una adecuada estrategia de selecci&oacute;n.