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

Bulb pungency, soluble solids content, and storage quality of 154 lines fro m the New Zealand Institute of Crop & Food Research Limited onion (Allium c epa L.) breeding programme were evaluated at Pukekohe and Lincoln, New Zeal and in the 1998/99 season. Within-site variation was controlled by an exper imental design incorporating systematically allocated mild and pungent chec k lines rather than blocking. Spatial trends in bulb composition were detec ted and adjustments made to models accordingly, suggesting that this is an appropriate and efficient means of compensating for within-site variation i n onion trials. The lines surveyed included many that were early, but few t hat were mild and/or had low soluble solids. Correlation between soluble,so lids content and storage loss was observed at both sites. The correlation o bserved between maturity (late and frequency of rots at Pukekohe was probab ly the result of greater impacts of onion thrip damage and wet weather on l ate-maturing lines. We conclude that although selection for storage and ear liness in this programme have been effective lower pungency may have been l ost from mild introductions through lack of deliberate selection.