Interaction between Dickeya dianthicola and Pectobacterium parmentieri in Potato Infection under Field Conditions

Dickeya and Pectobacterium spp. both cause blackleg and soft rot of potato, which can be a yield-reducing factor to potato production. The purpose of this study was to examine the interaction between these two bacterial genera causing potato infection, and subsequent disease development and yield responses under field conditions. Analysis of 883 potato samples collected in Northeastern USA using polymerase chain reaction determined that Dickeya dianthicola and P. parmentieri were found in 38.1% and 53.3% of all samples, respectively, and that 20.6% of samples contained both D. dianthicola and P. parmentieri. To further investigate the relationship between the two bacterial species and their interaction, field trials were established. Potato seed pieces of Russet Burbank, Lamoka, and Atlantic were inoculated with bacterial suspension of D. dianthicola at 10(7) colony-forming unite (CFU)/mL using a vacuum infiltration method, air dried, and then planted in the field. Two-year results showed that there was a high correlation (p < 0.01) between yield loss and percent of inoculated seed pieces. In a secondary field trial conducted in 2018 and 2019, seed pieces of potato Shepody, Lamoka and Atlantic were inoculated with D. dianthicola, P. parmentieri, or mixture of both species, and then planted. In 2019, disease severity index, as measured by the most sensitive variety Lamoka, was 16.2 with D. dianthicola inoculation, 10.4 with P. parmentieri, 25.4 with inoculation with both bacteria. Two-year data had a similar trend. Thus, D. dianthicola was more virulent than P. parmentieri, but the co-inoculation of the two species resulted in increased disease severity compared to single-species inoculation with either pathogen.

Automated summary

This study examined the presence of Dickeya dianthicola and P. parmentieri in potato samples collected in Northeastern USA, and conducted field trials to investigate their interaction and disease severity. The results showed that D. dianthicola was more virulent than P. parmentieri, but co-inoculation of both species led to increased disease severity compared to single-species inoculation.