A Solanum bulbocastanum gene has been cloned from a late blight-resistance locus and its sequence provided, together with the sequence of the encoded protein. DNA encoding the resistance protein has been introduced into potato plants and confers resistance to Phytophthora infestans, the causal agent of late blight. The resistance protein is in the class of Nucleotide Binding Site-Leucine-Rich Repeat Proteins (NBS-LRRP), and the gene in S. bulbocastanum is flanked by related NBS-LRRP gene sequences.