Casañas F., Plans M., Romero del Castillo R., Simó J., Valero J. (2013) Breeding onions (Allium cepa L.) for consumption as ‘calçots’ (second-year resprouts). Scientia Horticulturae. Volum 152, pg. 74-79.
Despite the expanding market for ‘calçots’, the second-year resprouts of the ‘Blanca Tardana de Lleida’ onion landrace, this product is still obtained from traditional populations. During a program devoted to the obtainment of improved varieties for number of commercial ‘calçots’ per onion, several experiments were undertaken to evaluate the efficiency of the process and develop breeding tools. The heritabilities estimated for the trait were very low, ranging from 0.14 to 0.24, contrasting with the advances achieved in the selection process (more than 100% in all cases). This is related with the high phenotypic variability of the trait, indicating that the low heritability is due to a very strong environmental component. The results also showed the importance of starting the selection process from large bulbs to allow the maximum productive potential of each genotype to be expressed. Slicing these bulbs transversely and counting the gemmae enables us to know the number of ‘calçots’ the onion will produce because the coefficient of correlation between gemmae and ‘calçots’ is 0.80 (p ≤ 0.001). Unfortunately, the lack of significant correlations between the characteristics of the bulb and the number of commercial ‘calçots’ per onion makes it necessary to finalize the selection on the second-year ‘calçot’-producing plant, but counting gemmae makes it possible to explore a large number of individual bulbs and simplifies the final phase of selection.