The present invention provides a polynucleotide which enables the modulation of the seed vigour, and in particular enhances the seed vigour, and more particularly enables the modification of the speed of germination. A plant seed comprising the said polynucleotide is also provided. A method of producing the plant seed, method for improving the germination and vigour of plant seed, transgenic plant and the use of the polynucleotide of the invention for producing plants growing seeds with improved germination and vigour characteristics are also provided. The invention particularly concerns Brassica, more particularly Brassica oleracea.