Common scab resistance in potato

Common scab disease of potato is distributed worldwide and not easily controlled. It is caused by Streptomyces species. The virulence mechanism of Streptomyces species is the production of thaxtomin A. Although the disease cycle of common scab of potato is well understood, the molecular processes underlying disease development and disease resistance are little known. The work performed in this thesis is a part of an on-going project on common scab resistance in potato, studying gene expression in response to S. turgidiscabies infection. Transcription profiles established by RNA-sequencing indicate a number of putative defense-associated genes which uniquely expressed in resistant cultivar Beate at the initial stage of tuber development. Seven candidate genes of which were selected to investigate the correlation between their expression and common scab resistance in potato, using real-time PCR method. Apart from these seven genes, two candidate genes putatively encoding TXR1 proteins involving in thaxtomin A transport, two putative candidate auxin signalingassociated genes and a gene putatively encoding aminotransferase ALD1 were also investigated. Comparisons of candidate gene expressions in resistant cultivars and susceptible cultivars indicate two selected candidate genes performed correlations between their expressions and common scab resistance, which are gene putatively encoding auxin binding protein 1 and gene putatively encoding aminotransferase ALD1. These findings putatively conceived of an idea that auxin signaling might promote common scab resistance in potato. On the other hand, the results are not in the agreement with the hypothesis that putative defenseassociated genes which uniquely expressed in resistant cultivar Beate at the initial stage of tuber development might enhance common scab resistance.M-P