Abstract
During the 2012/2013 growing season, potato tubers and stems showing rotting tissue and black discoloration, respectively, were obtained for analysis from Nyandarua and Mau Narok areas of Kenya, where potatoes are widely grown. During this period, more than 50% of the farms across Kenya reported cases of soft rot and blackleg diseases. Soft rot and blackleg diseases account for as much as 1/4 of the annual potato losses in Kenya. Bacteria from infected potato tuber and stem samples were isolated on nutrient agar then transferred to crystal violet polypectate medium (CVP) according to established standard procedures (3). All pit-forming (n = 48) strains were purified on nutrient agar and stored in 30% glycerol at –80°C for further use. All strains grew at 28°C and 37°C. PCR with pel gene specific primers (Y1/Y2) produced a 434-bp product and confirmed that all 48 strains have the gene sequence coding for pectate lyase specific for Pectobacterium spp. (1). Primers (Br1f/L1r) identified 1/3 of these strains as Pectobacterium carotovorum subsp. brasiliense based on their characteristic 322 bp (2). The other Pectobacterium spp. are currently undergoing further characterization. To further identify these pectolytic strains, a multi locus sequence typing (MLST) approach was employed (4). To this end, partial nucleotide sequences of the housekeeping genes mdh and gapA (accession nos. KF72004 to KF72009) showed 92% similarity to the Pcb1692 reference strain in GenBank. These results were in agreement with those obtained by species-specific primers. Phylogenetic analysis of the 679-bp concatenated partial gene sequences grouped strains collected in this study together with Pectobacterium subsp. brasiliense strains identified in other parts of the world with a 98% bootstrap support value. Three randomly selected Kenyan strains and Pcb1692 reference strain were inoculated into potato tubers in our research laboratory by making 1-cm holes into the tubers using a sterile pipette tip and thereafter injecting 10 μl (at 1.0 × 10 6 cfu/ml) into the tuber for pathogenicity assays. A negative control of 10 mM MgSO 4 was included and all the inoculated holes sealed with petroleum jelly to avoid contamination. This experiment consisted of five potato tubers per strain in three independent assays. All three representative strains induced water soaked soft symptoms similar to the symptoms previously observed on infected potato tubers. Furthermore, when bacterial suspensions of 1.0 × 10 6 cfu/ml isolated strains and the Pcb1692 reference strain were inoculated onto potato stems maintained at 28°C, blackleg and wilting of the stems occurred within a period of 3 to 21 days. No symptoms were observed in potato tubers or stems inoculated with the negative control (MgSO 4 ). PCR with Br1f/L1r primers confirmed that the re-isolated bacteria were P. carotovorum subsp. brasiliense. To our knowledge, this is the first occurrence of P. carotovorum subsp. brasiliense on potatoes in Kenya. References: (1) A. Darrasse et al. Appl. Environ. Microbiol. 60:1437, 1994. (2) V. Duarte et al. J. Appl. Microbiol. 96:535, 2004. (3) L. J. Hyman et al. Potato Res. 44:265, 2001. (4) Ma et al. Phytopathology 97:1150, 2007.
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Claims 11
Claim · model-written summary
About one third of the pectolytic isolates from potato were identified as Pectobacterium carotovorum subsp. brasiliense.
- Taxon
- Potatoes
Solanum tuberosumt0 - Interactor
- Pectobacterium carotovorum subsp. brasiliensePectobacterium brasiliensee1pathogen
- Outcome
- these strainse1
- Value
- 1/3e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“Primers (Br1f/L1r) identified 1/3 of these strains as Pectobacterium carotovorum subsp. brasiliense based on their characteristic 322 bp”
Claim · model-written summary
Kenyan strains grouped with Pectobacterium subsp. brasiliense strains from other regions, with a 98% bootstrap support value.
- Taxon
- PotatoesSolanum tuberosumt0
- Interactor
- Pectobacterium subsp. brasiliensee1pathogen
- Outcome
- grouped strains collected in this studye1
- Value
- 98%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“Phylogenetic analysis of the 679-bp concatenated partial gene sequences grouped strains collected in this study together with Pectobacterium subsp. brasiliense strains identified in other parts of the world with a 98% bootstrap support value”
Claim · model-written summary
The mdh and gapA partial sequences of the isolates showed 92% similarity to the Pcb1692 reference strain.
- Taxon
- PotatoesSolanum tuberosumt0
- Gene
- mdh and gapAe1
- Outcome
- similarity to the Pcb1692 reference straine1
- Value
- 92%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“partial nucleotide sequences of the housekeeping genes mdh and gapA (accession nos. KF72004 to KF72009) showed 92% similarity to the Pcb1692 reference strain in GenBank”
Claim · model-written summary
All three representative strains induced water-soaked soft symptoms in potato tubers.
- Taxon
- potato tuberse0
- Treatment
- All three representative strainse0
- Interactor
- strainse0pathogen
- Outcome
- water soaked soft symptomse0
Not reportedComparatorDirection
Verbatim
e0“All three representative strains induced water soaked soft symptoms similar to the symptoms previously observed on infected potato tubers”
Claim · model-written summary
Bacterial suspensions of the isolated strains and the Pcb1692 reference caused blackleg and wilting of potato stems within 3 to 21 days.
- Taxon
- potato stemse0
- Treatment
- bacterial suspensions of 1.0 × 10 6 cfu/mle0
- Interactor
- isolated strainse0pathogen
- Outcome
- blackleg and wilting of the stemse0
- Value
- 3 to 21 dayse0
Not reportedComparatorDirection
Verbatim
e0“when bacterial suspensions of 1.0 × 10 6 cfu/ml isolated strains and the Pcb1692 reference strain were inoculated onto potato stems maintained at 28°C, blackleg and wilting of the stems occurred within a period of 3 to 21 days”
Claim · model-written summary
The negative control (MgSO4) caused no symptoms in potato tubers or stems.
Not reportedComparatorDirection
Verbatim
e0“No symptoms were observed in potato tubers or stems inoculated with the negative control (MgSO 4)”
Claim · model-written summary
PCR confirmed that the re-isolated bacteria were Pectobacterium carotovorum subsp. brasiliense.
- Taxon
- PotatoesSolanum tuberosumt0
- Interactor
- P. carotovorum subsp. brasiliensePectobacterium brasiliensee1pathogen
- Outcome
- re-isolated bacteriae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“PCR with Br1f/L1r primers confirmed that the re-isolated bacteria were P. carotovorum subsp. brasiliense”
Claim · model-written summary
Pectobacterium carotovorum subsp. brasiliense was first recorded on potatoes in Kenya.
- Taxon
- potatoesSolanum tuberosume0
- Interactor
- P. carotovorum subsp. brasiliensePectobacterium brasiliensee0pathogen
- Outcome
- first occurrencee0
- Setting
- Kenyae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To our knowledge, this is the first occurrence of P. carotovorum subsp. brasiliense on potatoes in Kenya”
Claim · model-written summary
More than 50% of farms across Kenya reported cases of soft rot and blackleg in the 2012/2013 season.
- Taxon
- PotatoesSolanum tuberosumt0
- Outcome
- cases of soft rot and blackleg diseasese1
- Value
- more than 50%e1
- Setting
- across Kenyae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“more than 50% of the farms across Kenya reported cases of soft rot and blackleg diseases”
Claim · model-written summary
All strains grew at 28°C and 37°C.
- Taxon
- PotatoesSolanum tuberosumt0
- Outcome
- grewe1
- Qualifier
- at 28°C and 37°Ce1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“All strains grew at 28°C and 37°C”
Claim · model-written summary
PCR with pel gene primers confirmed that all 48 strains carry the pectate lyase gene sequence.
- Taxon
- PotatoesSolanum tuberosumt0
- Gene
- pel genee1
- Outcome
- have the gene sequence coding for pectate lyasee1
- Value
- all 48 strainse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soft Rot and Blackleg of Potatoes in Kenya”
e1“PCR with pel gene specific primers (Y1/Y2) produced a 434-bp product and confirmed that all 48 strains have the gene sequence coding for pectate lyase specific for Pectobacterium spp.”
The same questions in other papers
magnesium sulfate · disease · Solanum tuberosum (potato)Positive and negative results
1 in the opposite direction
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.