Abstract
Rhizogenic agrobacteria cause excessive root proliferation known as hairy root disease (HRD) on hydroponically grown tomato, cucumber, and eggplant, resulting in reduced yield (up to 10%) and severe economic losses worldwide (Bosmans et al. 2017). In 2018 and 2019, typical symptoms of HRD were observed in hydroponically grown bell pepper, specifically, Capsicum annuum cvs. Nagano (2018 and 2019), Lunik (2019), and Atlante (2018) in a commercial greenhouse located in the county Geumgok-myeon (province Gyeongsangnam-do, South Korea). Plants hydroponically grown on coco substrate showed excessive root formation, and this occurred on at least 50% of the plants in the greenhouse. Bacteria were isolated from symptomatic roots by plating a 10-fold dilution series on the semiselective 1A-Te medium (Bosmans et al. 2015, Brisbane and Kerr 1983). Six characteristic Agrobacterium colonies displaying a black color with a metallic shine were selected. Amplification of marker genes rolB and virD2 confirmed the presence of a root-inducing plasmid (pRi) (Bosmans et al. 2015). Partial 16S rRNA sequencing of the six colonies revealed the presence of only one unique isolate (strain PME19.1.1), which was identified as Agrobacterium (>99% sequence identity on a total of 564 bp). To enable a more precise classification, a multilocus sequence analysis based on four housekeeping genes (16S rRNA, recA, rpoB, and trpE loci) was performed as described previously (Bosmans et al. 2015). The resulting phylogenetic tree showed that PME19.1.1 can be classified as Agrobacterium genomospecies 9. Pathogenicity of isolate PME19.1.1 was confirmed in a bioassay using bell pepper cultivar Madison S&G (S. Rodriguez, personal communication). To confirm Koch’s postulates, three seedlings were inoculated and compared with a noninoculated plant. In addition to strain PME19.1.1, rhizogenic Agrobacterium strains ST15.13/097 and ST15.13/012, both isolated from tomato roots showing HRD symptoms in greenhouses in Belgium, were also included in the bioassay. After 9 weeks, plants were harvested to evaluate pathogenicity. Visual inspection for excessive root formation, wet weight, dry weight, and photographs of the roots were taken from each plant. A Kruskal–Wallis test using SPSS was conducted on each of the parameters measured. Visual inspection clearly showed that bell pepper inoculated with the three Agrobacterium strains resulted in excessive root proliferation. This was confirmed by significantly higher root fresh weight compared with the noninoculated control (P = 0.061). After the experiment, a specific quantitative PCR, targeting the ORF13 gene present in the pRi plasmid, was conducted and confirmed the presence of the rhizogenic agrobacterial DNA in the root samples of the inoculated plants but not in the control plants (protocol adjusted from Bosmans et al. 2016). Furthermore, bacteria were reisolated from the infected plants by plating root samples on 1A-Te medium. Sequence analysis of the rolB of the obtained clones demonstrated that it concerned the original isolate used for inoculation. To our knowledge, this is the first report of rhizogenic agrobacteria causing HRD in hydroponically grown bell pepper. Additionally, we demonstrated that rhizogenic Agrobacterium strains isolated from infected tomato plants are also able to infect bell pepper. Considering the current threat of HRD on tomato, this note highlights the potential of HRD to become an emerging disease in bell pepper cultivation as well.
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Claims 11
Claim · model-written summary
Bell pepper inoculated with three rhizogenic Agrobacterium strains shows excessive root proliferation compared with a noninoculated plant.
- Taxon
- bell peppert0
- Treatment
- inoculated with the three Agrobacterium strainse1
- Interactor
- Agrobacterium
.jpg?width=60)
Agrobacteriume1pathogen - Outcome
- excessive root proliferatione1
- Comparator
- a noninoculated plante2
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“Visual inspection clearly showed that bell pepper inoculated with the three Agrobacterium strains resulted in excessive root proliferation”
e2“three seedlings were inoculated and compared with a noninoculated plant”
Claim · model-written summary
Root fresh weight of inoculated bell pepper is significantly higher than the noninoculated control, P = 0.061 as reported.
- Taxon
- bell peppert0
- Treatment
- inoculated with the three Agrobacterium strainse1
- Interactor
- AgrobacteriumAgrobacteriume1pathogen
- Outcome
- root fresh weighte3
- Direction
- highere3
- Qualifier
- P = 0.061e3
- Comparator
- noninoculated controle3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“Visual inspection clearly showed that bell pepper inoculated with the three Agrobacterium strains resulted in excessive root proliferation”
e3“This was confirmed by significantly higher root fresh weight compared with the noninoculated control (P = 0.061)”
Claim · model-written summary
Rhizogenic agrobacterial DNA is present in the root samples of inoculated bell pepper but not in controls, by qPCR.
- Taxon
- bell peppert0
- Interactor
- rhizogenic agrobacteriale4pathogen
- Outcome
- presence of the rhizogenic agrobacterial DNAe4
- Qualifier
- targeting the ORF13 gene present in the pRi plasmide4
Not reportedDirection
Verbatim
t0“Hydroponic Bell Pepper Crop”
e4“a specific quantitative PCR, targeting the ORF13 gene present in the pRi plasmid, was conducted and confirmed the presence of the rhizogenic agrobacterial DNA in the root samples of the inoculated plants but not in the control plants”
Claim · model-written summary
Reisolated bacteria from infected bell pepper match the original isolate by rolB sequence.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e5“Sequence analysis of the rolB of the obtained clones demonstrated that it concerned the original isolate used for inoculation”
Claim · model-written summary
Isolate PME19.1.1 is pathogenic to bell pepper cultivar Madison S&G in a bioassay.
Not reportedDirection
Verbatim
t0“Hydroponic Bell Pepper Crop”
e6“Pathogenicity of isolate PME19.1.1 was confirmed in a bioassay using bell pepper cultivar Madison S&G”
Claim · model-written summary
Isolate PME19.1.1 can be classified as Agrobacterium genomospecies 9 by phylogenetic tree.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e7“The resulting phylogenetic tree showed that PME19.1.1 can be classified as Agrobacterium genomospecies 9”
Claim · model-written summary
Partial 16S rRNA sequencing identified isolate PME19.1.1 as Agrobacterium, with over 99 % sequence identity.
- Taxon
- bell peppert0
- Interactor
- AgrobacteriumAgrobacteriume1pathogen
- Outcome
- sequence identitye1
- Value
- >99%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“Partial 16S rRNA sequencing of the six colonies revealed the presence of only one unique isolate (strain PME19.1.1), which was identified as Agrobacterium (>99% sequence identity on a total of 564 bp)”
Claim · model-written summary
This is the first report of rhizogenic agrobacteria causing hairy root disease in hydroponically grown bell pepper.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“To our knowledge, this is the first report of rhizogenic agrobacteria causing HRD in hydroponically grown bell pepper”
Claim · model-written summary
Hydroponically grown bell pepper in a commercial greenhouse shows excessive root formation on at least 50 % of plants.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“Plants hydroponically grown on coco substrate showed excessive root formation, and this occurred on at least 50% of the plants in the greenhouse”
Claim · model-written summary
Typical HRD symptoms were observed in Capsicum annuum cultivars Nagano, Lunik and Atlante in a commercial greenhouse in 2018 and 2019.
- Taxon
- Capsicum annuum
Capsicum annuume1 - Material
- Nagano (2018 and 2019), Lunik (2019), and Atlante (2018)e1
- Outcome
- typical symptoms of HRDe1
- Setting
- commercial greenhousee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“typical symptoms of HRD were observed in hydroponically grown bell pepper, specifically, Capsicum annuum cvs. Nagano (2018 and 2019), Lunik (2019), and Atlante (2018) in a commercial greenhouse”
Claim · model-written summary
Rhizogenic Agrobacterium strains isolated from infected tomato are also able to infect bell pepper.
Verbatim
t0“Hydroponic Bell Pepper Crop”
e1“Additionally, we demonstrated that rhizogenic Agrobacterium strains isolated from infected tomato plants are also able to infect bell pepper”
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