Genotypic and environmental variation in bulb composition of New Zealand adapted onion ( Allium cepa ) germplasm

Abstract Bulb pungency, soluble solids content, and storage quality of 154 lines from the New Zealand Institute of Crop & Food Research Limited onion ( Allium cepa L.) breeding programme were evaluated at Pukekohe and Lincoln, New Zealand in the 1998/99 season. Within‐site variation was controlled by an experimental design incorporating systematically allocated mild and pungent check lines rather than blocking. Spatial trends in bulb composition were detected and adjustments made to models accordingly, suggesting that this is an appropriate and efficient means of compensating for within‐site variation in onion trials. The lines surveyed included many that were early, but few that were mild and/or had low soluble solids. Correlation between soluble solids content and storage loss was observed at both sites. The correlation observed between maturity date and frequency of rots at Pukekohe was probably the result of greater impacts of onion thrip damage and wet weather on late‐maturing lines. We conclude that although selection for storage and earliness in this programme have been effective lower pungency may have been lost from mild introductions through lack of deliberate selection.