Identification of Pectobacterium versatile Causing Blackleg of Potato in New York State

Biocontrol Mechanisms of Three Plant Essential Oils Against Phytophthora infestans Causing Potato Late Blight

Late blight, caused by the notorious pathogen Phytophthora infestans, poses a significant threat to potato (Solanum tuberosum) crops worldwide, impacting their quality as well as yield. Here, we aimed to investigate the potential use of cinnamaldehyde, carvacrol, and eugenol as control agents against P. infestans and to elucidate their underlying mechanisms of action. To determine the pathogen-inhibiting concentrations of these three plant essential oils (PEOs), a comprehensive evaluation of their effects using gradient dilution, mycelial growth rate, and spore germination methods was carried out. Cinnamaldehyde, carvacrol, and eugenol were capable of significantly inhibiting P. infestans by hindering its mycelial radial growth, zoospore release, and sporangium germination; the median effective inhibitory concentration of the three PEOs was 23.87, 8.66, and 89.65 μl/liter, respectively. Scanning electron microscopy revealed that PEOs caused the irreversible deformation of P. infestans, resulting in hyphal shrinkage, distortion, and breakage. Moreover, propidium iodide staining and extracellular conductivity measurements demonstrated that all three PEOs significantly impaired the integrity and permeability of the pathogen's cell membrane in a time- and dose-dependent manner. In vivo experiments confirmed the dose-dependent efficacy of PEOs in reducing the lesion diameter of potato late blight. Altogether, these findings provide valuable insight into the antifungal mechanisms of PEOs vis-à-vis late blight-causing P. infestans. By utilizing the inherent capabilities of these natural compounds, we could effectively limit the harmful impacts of late blight on potato crops, thereby enhancing agricultural practices and ensuring the resilience of global potato food production.

Reproducible Quantitative Trait Loci for Resistance to Soft Rot Caused by Dickeya dianthicola Derived from the Wild Potato Solanum microdontum (PI 458355) Are Located on Chromosomes 1, 3, and 5

The potato wild relative Solanum microdontum is a breeder-friendly source of genetic resistance to soft rot. Our objectives were to (i) identify loci associated with soft rot resistance in S. microdontum germplasm and (ii) develop bi-parental populations in a self-compatible S. tuberosum genetic background to recover segregating F2 progenies, construct a linkage map, and identify quantitative trait loci (QTLs). Under objective (i), tubers from 103 S. microdontum genotypes from the United States Potato Genebank were inoculated with a high virulence strain of Dickeya dianthicola, and lesion size was measured after a 24-h incubation period at 30°C. Association analysis using 3,490 polymorphic Infinium array SNP markers identified soft rot resistance loci on chromosomes 1, 2, 3, 5, 7, 8, 11, and 12. Under objective (ii), a resistant S. microdontum accession PI 458355 was crossed with a highly fertile, self-compatible, diploid S. tuberosum pollen parent (PI 654351) to generate segregating F2 populations. Composite interval mapping was conducted using a genetic linkage map with 970 GBS-based SNP markers. Reproducible QTLs were detected on chromosomes 1, 3, and 5, explaining 11, 13, and 23% of the phenotypic variation, respectively. Homozygous S. microdontum alleles at the QTL on chromosome 5 and heterozygous or homozygous S. microdontum alleles at QTLs on chromosomes 1 and 3 significantly decrease lesion size compared with the homozygous S. tuberosum parent. The germplasm created in these studies provides a resource for studying traits from S. microdontum, and we can use the advanced F2 selections for future potato improvement. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Occurrence, Characteristics, and qPCR-Based Identification of Pectobacterium versatile Causing Soft Rot of Chinese Cabbage in China

Pectobacterium is one of the most important genera of phytopathogenic bacteria. It can cause soft-rot diseases on a wide range of plant species across the world. In this study, three Pectobacterium strains (KC01, KC02, and KC03) were isolated from soft-rotted Chinese cabbage in Beijing, China. These three strains were identified as Pectobacterium versatile based on phylogenetic analysis of Pectobacterium 16S ribosomal RNA, pmrA, and 504 Pectobacterium core genes, as well as a genomic average nucleotide identity analysis. Their biochemical characteristics were found to be similar to the P. versatile type strain ICMP9168T but differed in response to citric acid, stachyose, D-glucuronic acid, dextrin, and N-acetyl-β-D-mannosamine. All of the tested P. versatile strains showed different carbohydrate utilization abilities compared with P. carotovorum and P. odoriferum, particularly in their ability to utilize D-arabitol, L-rhamnose, and L-serine. Under laboratory conditions, the maceration ability of P. versatile on Chinese cabbage was the highest at 28°C, compared with those at 13, 28, 23, and 33°C. Additionally, P. versatile could infect all of the 17 known Pectobacterium host plants, except for Welsh onion (Allium fistulosum). A SYBR Green quantitative PCR (qPCR) detection system was developed to distinguish P. versatile from other soft-rot bacteria based on the combined performance of melting curve (with a single melting peak at around 85°C) and fluorescence curve (with cycle threshold <30) when the bacterial genomic DNA concentration was in the range of 10 pg/µl to 10 ng/µl. This study is the first to report the presence of P. versatile on Chinese cabbage in China, as well as a specific and sensitive qPCR assay that can be used to quickly identify P. versatile. The work contributes to a better understanding of P. versatile and will facilitate the effective diagnosis of soft-rot disease, ultimately benefitting commercial crop production.

Phylogeographic Analysis of Soft-Rot-Causing Pectobacterium spp. Strains Obtained from Cabbage in Serbia

The aim of this study was to establish a link between genetic diversity and the geographic origin of Pectobacterium strains belonging to three species-P. carotovorum, P. versatile, and P. odoriferum-isolated from cabbage in Serbia by comparing their sequences with those of strains sourced from different hosts and countries in Europe, Asia, and North America. Phylogeographic relatedness was reconstructed using the Templeton, Crandall, and Sing's (TCS) haplotype network based on concatenated sequences of the housekeeping genes dnaX, icdA, mdh, and proA, while pairwise genetic distances were computed by applying the p-distance model. The obtained TCS haplotype networks indicated the existence of high intra-species genetic diversity among strains of all three species, as reflected in the 0.2-2.3%, 0.2-2.5%, and 0.1-1.7% genetic distance ranges obtained for P. carotovorum, P. versatile, and P. odoriferum, respectively. Five new haplotypes (denoted as HPc1-HPc5) were detected among cabbage strains of P. carotovorum, while one new haplotype was identified for both P. versatile (HPv1) and P. odoriferum (HPo1). None of the TCS haplotype networks provided evidence of significant correlation between geographic origin and the determined haplotypes, i.e., the infection origin. However, as haplotype network results are affected by the availability of sequencing data in public databases for the used genes and the number of analyzed strains, these findings may also be influenced by small sample size.

Pectobacterium versatile Bacteriophage Possum: A Complex Polysaccharide-Deacetylating Tail Fiber as a Tool for Host Recognition in Pectobacterial Schitoviridae

Novel, closely related phages Possum and Horatius infect Pectobacterium versatile, a phytopathogen causing soft rot in potatoes and other essential plants. Their properties and genomic composition define them as N4-like bacteriophages of the genus Cbunavirus, a part of a recently formed family Schitoviridae. It is proposed that the adsorption apparatus of these phages consists of tail fibers connected to the virion through an adapter protein. Tail fibers possess an enzymatic domain. Phage Possum uses it to deacetylate O-polysaccharide on the surface of the host strain to provide viral attachment. Such an infection mechanism is supposed to be common for all Cbunavirus phages and this feature should be considered when designing cocktails for phage control of soft rot.

Species of Dickeya and Pectobacterium Isolated during an Outbreak of Blackleg and Soft Rot of Potato in Northeastern and North Central United States

An outbreak of bacterial soft rot and blackleg of potato has occurred since 2014 with the epicenter being in the northeastern region of the United States. Multiple species of Pectobacterium and Dickeya are causal agents, resulting in losses to commercial and seed potato production over the past decade in the Northeastern and North Central United States. To clarify the pathogen present at the outset of the epidemic in 2015 and 2016, a phylogenetic study was made of 121 pectolytic soft rot bacteria isolated from symptomatic potato; also included were 27 type strains of Dickeya and Pectobacterium species, and 47 historic reference strains. Phylogenetic trees constructed based on multilocus sequence alignments of concatenated dnaJ, dnaX and gyrB fragments revealed the epidemic isolates to cluster with type strains of D. chrysanthemi, D. dianthicola, D. dadantii, P. atrosepticum, P. brasiliense, P. carotovorum, P. parmentieri, P. polaris, P. punjabense, and P. versatile. Genetic diversity within D. dianthicola strains was low, with one sequence type (ST1) identified in 17 of 19 strains. Pectobacterium parmentieri was more diverse, with ten sequence types detected among 37 of the 2015–2016 strains. This study can aid in monitoring future shifts in potato soft rot pathogens within the U.S. and inform strategies for disease management.