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The progeny of reciprocal crosses established between 8 different coloured strains were screened for the presence of primin, a compound with allergenic properties. Progenies of all strains except Donkerrose produced primin (p+). Of the 5 p- progenies of this strain, 4 were of the long styled form. Intercrossing these p- plants resulted in exclusively primin-free plants, but crosses with other (p+) plants generally yielded p+ progeny. In a cross of a p- plant with cv. Stadt Zurich (p+), 33 of 100 plants were primin free. F1 and backcross analyses suggested that primin production is controlled by a single gene, although this could not always be confirmed in the F2. (Abstract retrieved from CAB Abstracts by CABI’s permission)

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The long juvenile period and slow propagation of tulips are serious drawbacks in breeding. The Institute's programme is therefore aimed at the development of a method of early selection for forcing ability in seedling progenies.In earlier trials, comparing the behaviour of juvenile and adult bulbs of cultivars has yielded provisional criteria for pre-selection. These criteria have now been tested in some large progenies.It appeared that flowering date after forcing in the glasshouse -a measure for forcing ability -was correlated with both time of emergence and time of dying down during the juvenile phase.Pre-selection on these parameters can be carried out effectively during the second and third growth season in the field. At the end of the third season, the categories that are late for either character in both seasons may be discarded.