Chromosome numbers in potato cultivars hypersensitive to late blight

The chromosomes of twenty-four blight resistant potato cultivars produced from S. demissum x S. tuberosum hybrids were counted. Twenty-two cultivars had 2n=4x=48 chromosomes and two cultivars had 2n=4x+1=49 chromosomes. The implications of these results are discussed briefly in relation to previous studies and to potato breeding methods.