CGN maize collection

Composition

More than half of the accessions are landraces, among which a large part landraces that are collected during two collecting missions to Pakistan (Hashmi et al. 1981). This material is unique and probably only duplicated in the genebank at Islamabad, Pakistan. The value of this material for maize cultivation in Northwest Europe is limited because of its late flowering and subsequent late maturing. The number of accessions of cultivars and research material is rather low. Detailed information on the collection has been published by Van Soest and Boukema (1995).

There are only a handful of Dutch cultivars in the collection, that all originate from before 1960. There is only one Dutch landrace in the collection, originating from the province of Gelderland. A set of accessions from Portugal have been collected in the mountains and they were used in a breeding program for cold tolerance. The French landraces are from different localities, mainly of the southern parts of France including the Pyrenees.

Regeneration

Seeds are directly sown in the field in April. During April and May, the maize seedlings are covered with plastic fleece to stimulate early growth. The distance between the rows is 75 cm and after thinning, the plant distance in the row is 25 cm. Because mays is a wind pollinator, before flowering all developing cobs need to be covered with a bag. Also male inflorescences are covered in a bag for one day to keep out foreign pollen. Pollination is done by hand. Cross pollinations are then made according to the chain-pollination method, where from each plant both the male and female inflorescence are used to make separate crosses. At least 70 crossings are made per accession. After pollination the cobs are kept covered in a bag for a while. In October the cobs are harvested and after drying they are threshed.