Timely detection and study of the spread of new types of pectobacteria pathogenic for agricultural plants is important for monitoring diseases, improving their diagnostics and preventing their spread in potato growing regions. A team of authors, including employees of the Department of Plant Protection of the Timiryazev Academy, conducted a study of pathogens causing black leg and soft rot of potatoes. They carried out the work as part of the implementation of the NCMU project “Agrotechnologies of the Future”. 

Potato black leg (necrosis of the basal part of the stems) and the associated soft rot of tubers are among the most dangerous bacterial diseases, causing significant economic losses both during cultivation and during post-harvest storage. The causative agents of these diseases belong to the Enterobacteriaceae family, which includes various species of pectolytic bacteria from the genera Dickeya and Pectobacterium. The latter currently include 17 described species. Their diversity, plasticity and ability to survive even in harsh conditions, parasitizing on many alternative hosts, cause the widespread distribution and pathogenicity of the pathogens. In this regard, research aimed at monitoring and controlling the spread of these highly pathogenic microorganisms is especially necessary.

“The advent of NGS (next-generation sequencing) technologies has significantly expanded our understanding of bacterial genomics, including the genus Pectobacterium. It has become clear that this genus is very diverse, and NGS analysis has facilitated the identification of strains in culture collections and allowed us to describe several new species of Pectobacteria, such as P. punjabense. Currently, P. punjabense is perhaps one of the least studied species of the genus Pectobacterium that are pathogenic for potatoes,” said Anna Vasilyeva, a postgraduate student at the Department of Plant Protection at the Russian State Agrarian University – Moscow Agricultural Academy named after K.A. Timiryazev.

Scientists studied three strains of P. punjabense isolated in 2021 from potato tubers with symptoms of soft rot. Infected vegetables were found in the Kemerovo and Moscow regions. The study included a characterization of genomic diversity based on the results of whole-genome sequencing. Biochemical tests were carried out, and the ability of the strains to cause symptoms of black leg and soft rot on potatoes was confirmed. The features of the accumulation of pathogen biomass during cultivation in a liquid nutrient medium at different temperatures were assessed. A special analysis was developed for highly sensitive and specific characterization of P. punjabense strains, which can later be used in diagnostic systems.

“Due to the high genetic diversity of potato blackleg pathogens, it is possible to control the spread of these pathogens only through the continuous study of new species, followed by the improvement of diagnostic methods based on phylogenetic analysis data. The biochemical characteristics of the strains determined using the API 20E panel generally corresponded to the characteristics of Pectobacterium spp., with the exception of the inability of P. punjabense to oxidize mannitol and its ability to oxidize melibiose. These results may be of scientific interest for the characterization and comparison of different P. punjabense strains. The detection of P. punjabiense in the Russian Federation has expanded our understanding of the extent of the pathogen’s spread. Therefore, the development of an effective real-time PCR diagnostic system described in our article is necessary to monitor the spread of this pathogen,” added Fevzi Dzhalilov, Head of the Plant Protection Department at the Timiryazev Russian State Agrarian University.
It is worth noting that the work done is the first report on the discovery of the potato pathogenic species P. punjabense in the Russian Federation.