Yield and traits of bulb quality in the Spanish sweet onion cultivar ‘Fuentes de Ebro’ after selection for low pungency

The cultivar ‘Fuentes de Ebro’ is a mild, long-day onion grown in the Northeast of Spain. In this work we report the achievements of two cycles of selection in order to produce an ideotype that combines high yield and desirable bulb quality characters such as low pungency, high soluble solid content, adequate firmness and medium size. We first evaluated 12 selected half-sib families and the phenotypic variation observed for these four traits was analyzed, showing that these bulb characters were significantly affected by location, family and the interaction of both factors. The combined selection produced a significant decrease on pungency, while the other bulb quality related traits showed values similar to those of the unselected progeny. As pungency is positively correlated to bulb soluble solid content and negatively correlated to weight, our selection for multiple traits probably limited the unfavorable consequences of producing milder onions, which usually show large sizes, and low firmness and soluble solid content that reduces bulb conservation. We could estimate the realized heritability of pungency as H = 0.75, which is in agreement to previous studies. The two families with significantly lower pungency levels were reproduced and their progenies evaluated again. One of these families that showed lower pungency levels than unselected and commercial plants, while maintained soluble solid content, firmness and weight traits, is going to be submitted to be officially recognized as a conservation variety, which may guarantee the integrity of the desirable attributes that reside in the ‘Fuentes de Ebro’ cultivar.

► Two cycles of selection improved quality traits of an autochthonous onion cultivar.
► Realized heritability for low pungency was slightly higher than in other varieties.
► Combined selection avoided unfavorable consequences of breeding for low pungency.