Interaction Between Dickeya dianthicola and Pectobacterium parmentieri in Potato Infection Under Field Conditions

Authors: GE, T. - University Of Maine; JOHNSON, S. - University Of Maine Cooperative Extension; Larkin, Robert - Bob; HAO, J - University Of Maine

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2021
Publication Date: 2/21/2021
Citation: Ge, T., Johnson, S.B., Larkin, R.P., Hao, J. 2021. Interaction between Dickeya dianthicola and Pectobacterium parmentieri in potato infection under field conditions. Microorganisms. 9: 316. https://doi.org/10.3390/microorganisms9020316.
DOI: https://doi.org/10.3390/microorganisms9020316

Interpretive Summary: A major outbreak of a serious and damaging disease of potato plants, known as blackleg and soft rot of potato, caused primarily by the bacterial pathogens Dickeya and Pectobacterium spp., has resulted in significant economic losses in the Northeastern United States since 2015. 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. Field trials demonstrated the close relationship between percentage of infected seed pieces and yield losses. Seed piece infection with D. dianthicola alone resulted in greater disease severity than P. pectobacterium alone, but the combination of both bacteria resulted in much greater disease severity than either pathogen alone. Thus, potato BSR was often caused by a combination of pathogens, and these combinations result in greater disease than the individual pathogens. This research is useful for researchers to identify and understand the pathogens and their interactions responsible and associated with this disease and can be used to improve control strategies and mitigate disease losses.

Technical Abstract: 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 107 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 pathoge