Gene Rpi-bt1 from Solanum bulbocastanum Confers Resistance to Late Blight in Transgenic Potatoes

Phytophthora infestans, the causal agent of late blight is the most devastating pathogen of cultivated potato worldwide. Utilizing map based cloning; a genomic region containing a cluster of six nucleotide binding site-leucine-rich repeat resistance gene analogs was isolated from the wild potato species Solanum bulbocastanum. Four genes were pseudogenes, with coding sequences interrupted by either frame shift mutations or premature stop codons. However, neither of the two uninterrupted genes conferred resistance to P. infestans when introduced into susceptible potatoes. Specific primers for one of the pseudogenes were used to amplify an uninterrupted cDNA from P. infestans-infected S. bulbocastanum leaves. A corresponding gDNA was amplified from a late blight-resistant bulbocastanum-tuberosum introgression line (Rpi-bt1). The Rpi-bt1 gene under transcriptional control of the constitutive potato Ubi3 promoter was found to confer resistance to P. infestans in several transgenic potato lines in a whole plant greenhouse assay.