Plant pathogens pose a significant threat to agricultural productivity and food security worldwide. The use of traditional chemical pesticides for plant disease management raises concerns due to the ...emergence of pesticide resistance and their potential adverse effects on human health and the environment. As a result, there is a growing interest in exploring alternative approaches for plant disease control. This review provides an overview of the antimicrobial potential of some plant-derived compounds, including essential oils, plant extracts, wastes and their major constituents, against plant pathogenic bacteria. The antimicrobial activity is attributed to the diverse chemical composition of these plant-derived compounds and their ability to target multiple cellular processes in pathogens’ cells. Furthermore, the review explores the use of some antagonistic bacteria and fungi as control tools. These beneficial microorganisms have shown promising results in suppressing the growth of plant pathogens through various mechanisms such as competition, antibiosis and induced systemic resistance. This review discusses the advantages and limitations of using plant-derived compounds and antagonistic microorganisms for plant disease management. Moreover, it highlights the need for further research to optimize their efficacy, develop sustainable formulations and evaluate their performance under field conditions.
Strains of
pv.
(
), isolated from infected olive trees (
L.) in three European countries (Croatia, Slovenia and Portugal) were identified and characterised according to their colony morphology, ...physiological and biochemical features. According to the LOPAT scheme, 38.6% of
isolates were grouped in the Ib cluster. The Portuguese
strains were fully consistent with the typical LOPAT profile for this bacterium. Conversely, most Slovenian
strains showed delayed oxidase activity, whilst Croatian
strains did not produce any fluorescent pigment when grown in vitro. For
molecular identification, both end-point and real-time PCR were used, as well as MALDI-TOF, which was additionally used for proteomic analysis and the subsequent species identification of a number of strains that showed deviations from expected LOPAT results.
was confirmed as a causal agent of olive knot disease in 46.6% of olive orchards screened. Overall, these data suggests a possible correlation of certain
features with the geographical origin and the ecological niche of
isolates.
Abstract
Raspberry bushy dwarf virus (RBDV), recently renamed to
Idaeovirus rubi
, is one of the most common viruses infecting
Rubus
species worldwide but there is still a limited number of genome ...sequences available in the GenBank database and the majority of the sequences include partial sequences of RNA‐1 and RNA‐2. The distribution and incidence of RBDV in main raspberry and blackberry growing provinces in Turkey were monitored during 2015–2019 and 537
Rubus
spp. samples were tested by both DAS‐ELISA and RT‐PCR. Among the tested samples, 36 samples tested positive for RBDV by DAS‐ELISA and 67 samples by RT‐PCR. There was relatively low nucleotide diversity among the Turkish isolates. Turkish isolates shared 93%–97.7%, 84.3%–98.9%, and 85%–99.2% nucleotide sequence identities with available sequences in the GenBank, in partial RNA‐1, movement protein (MP) and coat protein (CP) genes, respectively. In the phylogenetic tree constructed for RNA‐1, MP, and CP sequences, all Turkish raspberry isolates were clustered in a distinct clade. However, the blackberry isolates showed considerable variation in nucleotide sequences and were placed in three distinct groups. The divergent blackberry isolates showed high variability in MP (84.5%–89.3%) and CP (85.5%–89.7%) regions and were placed in a distinct group. The rest of blackberry isolates clustered together with sweet cherry RBDV isolates adjacent to the grapevine clade or together with raspberry isolates. The comparative analysis conducted on three RNA segments of RBDV highlighted the high sequence diversity of Turkish RBDV isolates. This study also emphasizes the importance of regular monitoring of RBDV infections in Turkey, with special regard to those
Rubus
spp. and grapevine accessions employed in conservation and selection programmes. In particular, the presence of new RBDV genetic variants and infection of
Rubus
species must be taken into account to choose a correct detection protocol and management strategy.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Olive knot disease, caused by the bacterium Pseudomonas savastanoi pv. savastanoi, causes great damage in olive orchards. While control measures of P. savastanoi pv. savastanoi in olive orchards ...primarily rely on pruning and copper-based treatments, the use of antibiotics as bactericidal preparations in agriculture is limited and highly restricted. However, plants are naturally endowed with protective molecules, such as phenolic compounds, which defend them against herbivores, insects, and microorganisms. This research aimed to test the virulence of five strains of P. savastanoi pv. savastanoi isolated from different growing regions and olive varieties, and to examine whether there is a difference in plant susceptibility based on the variety. An additional goal was to test the antimicrobial activity of olive mill wastewater, known for its high content of phenolic compounds, and aqueous garlic hydrolysate, as well as to compare them with a commercial copper-based product, pure hydroxytyrosol, and a standard antibiotic as references. Analysis of knot characteristics showed variations in the virulence of the P. savastanoi pv. savastanoi strains, with the highest virulence being observed for the strain I7L and the lowest virulence for the strain B45C-PR. The olive cultivar Rosinjola displayed higher susceptibility compared to Frantoio, Buža, and Leccino, while cv. Istarska bjelica exhibited the least susceptibility compared to the other investigated olive cultivars. In an attempt to explore alternative solutions for disease control, in vitro tests revealed that the phenol HTyr, GE, and the wastewater with the highest total phenolic content (cv. Istarska bjelica) possess the highest antibacterial activity. This supports the role of polyphenols in host defense, aligning with previous field observations of lower susceptibility of cv. Istarska bjelica to olive knot disease. These findings highlight the complex nature of olive knot interactions with bacterial strains and olive cultivars, simultaneously accentuating and underscoring the importance of considering the host’s defenses as well as bacterial virulence in disease management strategies.
Five isolates of a new member of the family
, tentatively named blackcurrant leafroll-associated virus 1 (BcLRaV-1), were identified in the currant. The 17-kb-long genome codes for 10 putative ...proteins. The replication-associated polyprotein has several functional domains, including papain-like proteases, methyltransferase, Zemlya, helicase, and RNA-dependent RNA polymerase. Additional open reading frames code for a small protein predicted to integrate into the host cell wall, a heat-shock protein 70 homolog, a heat-shock protein 90 homolog, two coat proteins, and three proteins of unknown functions. Phylogenetic analysis showed that BcLRaV-1 is related to members of the genus
, whereas recombination analysis provided evidence of intraspecies recombination.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The phylogeny, identification, and characterization of 33
isolates originating from 17 agricultural soils from 11 countries were analyzed on the basis of whole genome sequencing. Phylogenetic ...analyses revealed all isolates are divided into six groups, which follows the generally accepted phylogenetic division of
isolates. Four different identification methods resulted in a variation in the identity of the isolates, as none of the isolates were identified as the same species by all four methods-only the recent identification method proposed directly reflected the phylogeny of the isolates. This points to the importance of describing the basis and method used for the identification. The presence and percent identity of the protein product of 19 genes potentially involved in pathogenicity divided the 33 isolates into groups corresponding to phylogenetic division of the isolates. This suggests that different pathotypes exist and that it is possible to differentiate between them by comparing the percent identity of proteins potentially involved in pathogenicity. This also reveals that a basic link between phylogeny and pathogenicity is likely to exist. The geographical distribution of the isolates is not random: they are distributed in relation to their division into the six phylogenetic groups, which again relates to different ecotypes with different temperature growth ranges. This means that we find it easier to analyze and understand the results obtained from the 33
isolates in a phylogenetic, patho-type and ecotype-oriented context, than in a context based on uncertain identification at the species level.
High-throughput sequencing (HTS), more specifically RNA sequencing of plant tissues, has become an indispensable tool for plant virologists to detect and identify plant viruses. During the data ...analysis step, plant virologists typically compare the obtained sequences to reference virus databases. In this way, they are neglecting sequences without homologies to viruses, which usually represent the majority of sequencing reads. We hypothesized that traces of other pathogens might be detected in this unused sequence data. In the present study, our goal was to investigate whether total RNA-seq data, as generated for plant virus detection, is also suitable for the detection of other plant pathogens and pests. As proof of concept, we first analyzed RNA-seq datasets of plant materials with confirmed infections by cellular pathogens in order to check whether these non-viral pathogens could be easily detected in the data. Next, we set up a community effort to re-analyze existing Illumina RNA-seq datasets used for virus detection to check for the potential presence of non-viral pathogens or pests. In total, 101 datasets from 15 participants derived from 51 different plant species were re-analyzed, of which 37 were selected for subsequent in-depth analyses. In 29 of the 37 selected samples (78%), we found convincing traces of non-viral plant pathogens or pests. The organisms most frequently detected in this way were fungi (15/37 datasets), followed by insects (13/37) and mites (9/37). The presence of some of the detected pathogens was confirmed by independent (q)PCRs analyses. After communicating the results, 6 out of the 15 participants indicated that they were unaware of the possible presence of these pathogens in their sample(s). All participants indicated that they would broaden the scope of their bioinformatic analyses in future studies and thus check for the presence of non-viral pathogens. In conclusion, we show that it is possible to detect non-viral pathogens or pests from total RNA-seq datasets, in this case primarily fungi, insects, and mites. With this study, we hope to raise awareness among plant virologists that their data might be useful for fellow plant pathologists in other disciplines (mycology, entomology, bacteriology) as well.
Raspberry bushy dwarf virus (RBDV) is a long-known virus naturally infecting
Rubus
and grapevine. It is also one of the economically most important viruses of raspberries, but there are only a ...limited number of sequences covering a substantial part of the genome available in the databases. The aim of this study was: i) to study the geographic distribution of RBDV in Slovenia, and ii) to sequence RNA2 of several red raspberry and grapevine RBDV isolates and study their phylogeny and population structure. Geographic distribution studies were performed over a period of 13 years in three wine-growing regions of Slovenia (Primorska, Podravje and Posavje). The highest incidence of RBDV was found in Podravje (58.8%) and the lowest in Primorska (5.1%). Big differences were observed between Vipavska dolina (10.2%) and three other wine-growing districts of Primorska region (0.4–1.2%). Almost complete RNA2 sequences were obtained for four red raspberry isolates and seven grapevine isolates. Additionally, only coat protein sequences were obtained for three red raspberry isolates. Phylogenetic and population diversity analyses were performed on all available RBDV sequences. Phylogenetic analysis has shown clear differences in sequences from
Rubus
and grapevine that form two highly supported clades. In RNA2 analysis additional two sub-clades were found in grapevine clade. Two major subclades were identified also in the
Rubus
clade with further differentiation within these subclades. Purifying or stabilizing selection was found to be acting on both, CP and MP genes while few codons were found to be under positive selection.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Plant pathogenic bacteria pose a significant threat to olive cultivation, leading to substantial economic losses and reduced yield. The efficacy of antimicrobial agents against these pathogens is of ...great interest for sustainable disease management strategies. As such, the management of olive knot disease is one of the major challenges in olive protection. In the presented study, through a series of in vitro assays, we investigated the antimicrobial effect of six essential oils (EOs) and their most concentrated constituents against causative agent of olive knot disease—Pseudomonas savastanoi pv. savastanoi, highlighting the high potential of Origanum compactum EO and its constituent carvacrol. Carvacrol exhibited the highest potential for practical application, demonstrating membrane disruption as its mechanism of action even at the lowest concentration. The bactericidal effect of antimicrobials was confirmed in a time–kill assay, where concentrations of MIC, 2× MIC, and 4× MIC were evaluated. Some of the applied treatments resulted in inhibition equal or higher than copper-based treatment. Additionally, we assessed the phytotoxicity of carvacrol by foliar application on olive cv. Leccino. The appearance of phytotoxic injuries majorly occurred on the young leaves of olive plants, with the highest proportion of damaged canopy observed when the 2× MIC concentration was applied. Due to its great efficiency against P. savastanoi pv. savastanoi in vitro, these findings highlight the potential of carvacrol as a molecule of interest for the development of environmentally friendly biopesticides. This study also contributes to the advancement of disease management practices in olive cultivation, leading to enhanced crop protection.
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