The occurrence of bacteria from different species of Pectobacteriaceae on seed potato plantations in Poland

Bacteria from the genera Dickeya and Pectobacterium, the causative agents of soft rot and blackleg, trigger significant economic losses in potato production worldwide. Efficient struggle with these phytopathogens is highly challenging taking into consideration the lack of available control procedures. As only preventive measures are accessible, we decided to provide insight into the soft rot Pectobacteriaceae (SRP) present in Poland. During the growing seasons of 2013 and 2014, altogether 531 potato plants were collected from 138 seed potato fields and 23 storage facilities. Plant origin of the isolated bacteria, frequencies of coinfections with different species, the affected potato cultivars in addition to seasonal variation in the occurrence of SRP were studied. It was shown that bacteria from the Pectobacterium genus were abundant and outnumbered the ones classified to Dickeya spp. The vast majority of strains was isolated from the plant samples collected in July 2013 or in June–July 2014. The presence of all taxa of interest: Pectobacterium atrosepticum, Pectobacterium carotovorum, Pectobacterium parmentieri, Dickeya dianthicola and Dickeya solani were confirmed in July each year. We were able to isolate bacteria from the genus Dickeya and Pectobacterium from 35 out of 58 potato cultivars tested. The majority of SRP was isolated from potato stems, not from potato tubers. In four cases, coinfections of potato samples with even three diverse species of SRP, i.e. P. atrosepticum, P. carotovorum and P. parmentieri, were noted. It seems that since the first documented appearance of Dickeya solani in Poland in 2005, this pathogen has not played a dominating role in our country. The reported data describing the appearance and distribution of SRP in Poland might allow for prediction of the risks associated with infections initiated by these bacteria.