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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #376491
Research Project: Enhanced Alfalfa Germplasm and Genomic Resources for Yield, Quality, and Environmental Protection

Location: Plant Science Research

Title: Bacterial stem blight of alfalfa: An emerging disease in the United States caused by Pseudomonas syringae pv. syringae and Pseudomonas viridiflava

Author
item LIPPS, SAVANA - University Of Minnesota
item Samac, Deborah - Debby

Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/28/2021
Publication Date: 12/30/2020
Citation: Lipps, S., Samac, D.A. 2020. Bacterial stem blight of alfalfa: An emerging disease in the United States caused by Pseudomonas syringae pv. syringae and Pseudomonas viridiflava[abstract]. American Phytopathological Society. Plant Health 2020, August 10-14, 2021, p. 176. https://doi.org/10.1094/PHYTO-110-12-S2.207.

Interpretive Summary:

Technical Abstract: In the Intermountain West, alfalfa producers have observed significant damage from frosts in both spring and fall, setting back growth and reducing yields. Associated with frost damage is damage from the disease bacterial stem blight (BSB), caused by the ice nucleation-active bacterium Pseudomonas syringae pv. syringae (phylogroup 2b of the P. syringae complex). The bacterium promotes frost formation, penetrates stems at frost injury sites, and subsequently decays leaves and stems. Recently, another related bacterial species, Pseudomonas viridiflava (Pv) in phylogroup 7a, was also identified as a causal agent BSB. Although Pv has low ice nucleation activity, it produces high levels of pectolytic enzymes, which likely contribute to the disease. Here, the genetic diversity of a population of Pss and Pv isolates from several locations across the United States was analyzed via multi-locus sequence analysis using the housekeeping genes gyrB, gapA, gltA, and rpoD. Isolate virulence data from inoculation of alfalfa were also collected. The data from this research indicates that the pathogen population is widespread on alfalfa in the United States and genetically similar, suggesting that there has not yet been pressure on the population to evolve. Although the population is largely homogenous, there is still a fair amount of diversity in the population given by SNPs that suggest that the pathogen was not recently introduced. Future work will include whole genome sequencing and comparison of high and low-level virulent Pss and Pv isolates, as well as ice nucleation assays.