Abstract: Through cDNA-AFLP analysis of Four pools with different phenotypes of Six avirulence genes in germinating cysts of Phytophthora infestans, totally 85 candidate transcript derived fragments (TDFs) were obtained, including 20 for Avr1 , 28 for Avr2 , 16 for Avr32A vr102A vr11 , and 21 for A vr4 , respectively. One candidate TDF of linkage genes Avr3-Avr10-Avr11 (A11T13Avr3-10-11S157 ) and two candidate TDFs of A vr4 (A24T19Avr4S122 and A24T24A vr4S142 ) were identified through verification of expression of these TDFs in 20 P. infestans individuals. The results of Blast analysis showed that A11T13A vr3-10-11S157 was homologous with EST G001F101XT7 deposited in the Phytophthora germinating sporangium EST library, A24T19 A vr4S122 was identical with part of EST PH051G101XT7 deposited in the Phytophthora germinating cyst EST library while A24T24A vr4S142 had 98% similarity to
EST PH051G101XT7. That would facilitate cloning of full-length Avr4 gene by in silico cloning along with RACE (Rapid Amplification of cDNA Ends) technique.

Key words: Phytophthora infestans, Racespecific avirulence genes, cDNA-AFLP, Candidate transcript derived fragments