most or almost all other loci the last backcross generation would be selfed to give pure breeding progeny for the trait being transferred when a plant of inbred spinach line sp6504 representative seed of which having been deposited under ncimb accession no ncimb 41759 is used in backcrossing offspring retaining the combination of traits including medium bolting light green leaf color at maturity medium growth rate arrow shaped leaf round pointed leaf tip and resistance against downy mildew peronospora farinose f sp spinaciae pfs races 1 to 7 9 and 11 are progeny within the ambit of the invention backcrossing methods can be used with the present invention to improve or introduce a characteristic into a plant of the invention being a plant of inbred spinach line 6504 see e g u s pat no 7 705 206 incorporated herein by reference consistent with the above incorporation by reference section for a general discussion relating to backcrossing the invention further involves a method of determining the genotype of a plant of inbred spinach line sp6504 representative seed of which has been deposited under ncimb accession no ncimb 41759 or a first generation progeny thereof comprising obtaining a sample of nucleic acids from said plant and detecting in said nucleic acids a plurality of polymorphisms this method can additionally comprise the step of storing the results of detecting the plurality of polymorphisms on a computer readable medium and or transmitting the results of detecting the plurality of polymorphisms e g by telephony or by.