Abstract: The resistance of potato broad spectrum resistance gene Rpi-blb1（cloned from Solanum bulbocastanum）and its homologues Rpi-sto1（cloned from Solanum stoloniferum）and Rpi-pta1（cloned from Solanum papita）might be broken by advanced Phytophthora infestans isolates. Isolates potentially breaking this resistance could be found in Dutch potato fields on accessions of S. bulbocastanum and S. stoloniferum with these R-genes and in Mexico in nature on the same species. Here, these isolates have been retested on
transgenic Desiree containing Rpi-blb1, Rpi-sto1 or Rpi-pta1 and on accessions of all three species（blb8005, sto389-4 and pta767-1）which are harboring one of the three cloned R-genes. It turned out that two isolates
from Mexico, Pic99189 and Pic99192, found on S. stoloniferum, have broken the resistance from Rpi-blb1, Rpi-sto1 and Rpi-pta1 in cv. Desiree background. In addition, it was observed that the accessions harboring
the same R-gene still were resistant to these isolates except Pic99192, which had clearly broken the S. papita accession. Another observation was that transgenic plants need be selected for strong expression of resistance
to P. infestans in detached leaf assay (DLA). A pilot experiment with a Rpi-sto1 containing Desiree transformant，inoculated with Chinese isolates originated from 4 regions, showed high level of resistance and its potential application in China.

Key words: potato, late blight, homologous resistance genes