Abstract：A bacterial blotch disease, caused by Pseudomonas syringae pv. averrhoi is one of the most damaging disease of carambola(Averrhoa carambola). A polymerase chain reaction(PCR) protocol was developed to specifically detect Ps. syringae pv. averrhoi based on internally transcribed spacer(ITS) region of 16S~23S ribosomal. PCR products from the 16S~23S rDNA of Ps. syringae pv. averrhoi were cloned and sequenced. Based on a multiple sequences alignment among these obtained sequences, a pair of specific PCR primers PsaveF(5'-CTTATCGACGACTCAGCTGCG-3')/PsaveR(5'-TCATGCGTTGATCGTCAGGATC-3') were designed. The primer pairs amplified a single 373 bp product from all isolates of Ps. syringae pv. averrhoi that was not amplified from any other isolates tested. The sensitivity of detection with primers PsaveF / PsaveR was 10 pg genomic DNA. It could amplified a specific single product from natural infected carambola that was not amplified from healthy tissue. The results showed that the PCR protocol provides a rapid, sensitive and reliable tool routine detection and identification of Ps. syringae pv. averrhoi. In addition, the classification implication of ITS sequence homology was found by comparing sequences from Ps. syringae pv. spp. This study is beneficial to control the bacterial blotch disease of carambolan.
