Compatible- and incompatible-type interactions related to defense genes in potato elucidation by Pectobacterium carotovorum

The soft rot caused by Pectobacterium carotovorum subsp. carotovorum is the most harmful and damaging bacterial diseases of seed potato production in Egypt. In this study, two cultivars of potato (Nicola-likely resistant and Ladypalfor-likely susceptible) were used to quantify the differentially expressed genes in the infected leaves and characterize their expression levels during pathogencity process. The two potato cultivars were grown in sand-beet moss pots and then inoculated by Pectobacterium. The inoculated potato tissues were taken on intervals, and gene expression analysis was conducted using both of differential display PCR and real-time PCR techniques. Different down-regulated and up-regulated genes were observed in samples treated with P. carotovorum subsp. carotovorum PCCS63 isolate compared with control (non-infected). High numbers of differentially expressed genes were obtained by the differential display, and it was noticed that the genetic variability was vigorously shown in the samples taken after 24 h post-inoculation. The same observation was demonstrated by the real-time PCR results, which indicated that the highest expression level of the CHS gene in Ladypalfor tissues was 24 h post-inoculation, but it was very low expressed in the control plants. On the contrary, both the PR2 and PR5 genes were suppressed in the infected potato tissues when compared with the control. Moreover, suppression of PR2 and PR5 reached its maximum level 24 h post-inoculation. It can be concluded that the plant pathogen P. carotovorum succeeded in making suppression for PR2 and PR5 genes but failed to resist elevated level of the induced CHS gene during the infection.