EVALUATION OF SPANISH ONION LANDRACES FOR INCORPORATION INTO ORGANIC FARMING

Abstract

Ten Spanish landraces of onion (Allium cepa L.), nine of them coming from the genebank of the COMAV, and one commercial cultivar, as control, were assayed during 2009 in the Centro de Investigacion Agraria Finca “La Orden-Valdesequera”, Extremadura (Spain). The trial was conducted using techniques that conform to legislation in organic agriculture. The harvested bulbs were graded by equatorial diameter into five categories according to quality standard for onions in the Spanish market. Total commercial yield (t ha-1), percentage of weight of each category over total weight and average bulb weight (g) were obtained. A sample from each cultivar was used to measure refractive index (°Brix) and pH. Average polar and equatorial diameters (mm) were determined and IPGRI descriptor was used in the morphological characterization of the following bulb characters: bulb shape, population uniformity of bulb shape, bulb fresh colour and bulb skin colour. The average yields of five landraces were higher than the rest of cultivars, four of them exceeding more than twice the production of the control. These five landraces had an equatorial diameter greater than 120 mm in more than 60% of their production and an average bulb weight over 500 g. The average °Brix values of the landraces ranged between 6.0±0.1 and 10.0±0.7. Negative correlations between soluble solids content and average bulb weight and average polar and equatorial diameters, were detected. The °Brix values were typical of onion for fresh market due to the low suitability for conservation. These results show that it could be possible the commercial production of some of the tested landraces under organic agriculture techniques.