Determination of the presence of pathogenic island in causative agents of potato common scab

Darya Roslyakova

Bachelor's thesis

Abstract:

Common scab is one of the most widespread and known potato diseases, which is caused by actinobacterial pathogen belonging to several species of the genus Streptomyces. In the current work, the presence of genes coding for the common scab pathogenicity determinant, dipeptide thaxtomin, along with other virulence factors frequently present in thaxtomin-pathogenicity island were determined. Various bacterial strains were isolated from tuberosphere of potatoes with different common scab severity levels and geographically distinct localities. There were 134 strains isolated from several potato cultivars grown at several locations in the Czech Republic and South America. The strains were isolated and cultivated on R2A agar medium and then the same liquid medium. Their DNA was extracted, and PCR was performed for genes 16S, stx1 a/b, TxtBC1_F/R, Tom 3/4, P19 f/r and Nec f/r. The results were analyzed using sequencing and a phylogenetic tree was created to demonstrate relatedness between the strains. The results supported our hypothesizes that the presence of potato common scab depends also on the environmental conditions such as the location of origin or a local pool of pathogenic bacteria; and that sites would differ in the dominant pathogenic island type. Moreover, it was found that genes for thaxtomin may be horizontally transferred not only within the Streptomyces genus, but among other distantly related actinobacterial genera such as Nocardia, Nonomureae, Promicromonospora, and Micromonospora, and the genes can even be found in gram-negative phylum Proteobacteria in genera Phyllobacterium, Pseudomonas, Azamonas, and others. Lastly, it was recorded that Nec genes are involved in pathogenicity and might be linked to the thaxtomin A biosynthetic genes.

Keywords

potato common scab, Streptomyces spp., Actinobacteria, pathogenicity, pathogenic islands

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 1. 5. 2021

Obhajoba závěrečné práce

• Vedúci: doc. RNDr. Markéta Marečková, Ph.D.

Czech University of Life Sciences Prague

Faculty of Agrobiology, Food and Natural Resources

Bachelor programme / odbor:
Agriculture and Food / Agriculture and Food