Abstract
During surveys covering 60 cassava (Manihot esculenta Crantz) fields, randomly selected (between latitude 4°55'N and 8°16'N) in south Ghana, and 27 fields in southeast (between 4°50'N and 7°56'N) Nigeria, 8-month-old or older stems of some cassava genotypes were found to be covered by grayish brown lesions, predominantly on lignified portions of stems. Field disease incidence ranged from 0 to 80%, and severity from no disease to highly affected (>15 lesions per stem). To identify the pathogen, infected stem portions were cut out, surface disinfected, and cultured on potato dextrose agar (PDA) acidified with 0.4% (vol/vol) lactic acid. After 1 week, mycelia, conidiophores, and conidia were observed under a microscope, and the pathogen was identified as Curvularia lunata (Wakk.) Boedijn (confirmed also by the International My-cological Institute, Surrey, U.K.). To complete Koch's postulates, stem pieces of four cassava cultivars (Agric, Tchukunochi, TMS 30572, and Ben 86052), were disinfected in hot water (52°C for 5 min), transplanted in sterilized sand, and maintained in a greenhouse under natural light at 28 to 30°C. Before planting, five stems were wound inoculated (sliced with an epidermal scalpel) just above nodes, and a 5-mm-diameter PDA mycelial plug of C. lunata was applied to each wound or directly to unwounded nodes. Stems were then kept in a plastic bag for 24 h before planting. For each cultivar, five control stem pieces were similarly wounded but not treated with PDA plugs. All plants were maintained under >90% relative humidity. Control plants remained symptom-free whereas lesions and bud necrosis similar to field symptoms were observed on all inoculated plants within 1 month. Symptom development was quicker (2 to 3 weeks) on wound-inoculated than on nonwounded stems. Mortality of artificially wound-inoculated buds ranged between 30 and 100%, depending on genotype and manner of inoculation. Artificially infected stem and bud portions plated on PDA consistently yielded C. lunata. Bud sprouting of naturally infected cuttings was monitored over a period of 4 weeks after stem planting. When buds were completely colonized, sprouting was completely inhibited. However, partially colonized buds sprouted, but growth was reduced by 20 to 50% (depending on genotype), compared with healthy stems. This is the first report of C. lunata pathogenic on cassava.
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Claims 11
Claim · model-written summary
In surveys of cassava fields in south Ghana and southeast Nigeria, stems of some cassava genotypes were covered by grayish brown lesions, mainly on lignified stem portions.
- Taxon
- cassava
Manihot esculentae0 - Organ / stage
- stemse0
- Outcome
- grayish brown lesionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“8-month-old or older stems of some cassava genotypes were found to be covered by grayish brown lesions”
Claim · model-written summary
Field disease incidence in the surveyed cassava fields ranged from 0 to 80%.
- Taxon
- CassavaManihot esculentat0
- Outcome
- Field disease incidencee0
- Value
- 0 to 80%e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“Field disease incidence ranged from 0 to 80%”
Claim · model-written summary
Disease severity in the surveyed cassava fields ranged from no disease to highly affected stems with more than 15 lesions per stem.
- Taxon
- CassavaManihot esculentat0
- Outcome
- severitye0
- Value
- >15 lesions per steme0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“severity from no disease to highly affected (>15 lesions per stem)”
Claim · model-written summary
The pathogen isolated from infected cassava stems was identified as Curvularia lunata, confirmed by the International Mycological Institute.
- Taxon
- CassavaManihot esculentat0
- Interactor
- Curvularia lunata
Curvularia lunatae0pathogen - Outcome
- pathogen was identified as Curvularia lunatae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“the pathogen was identified as Curvularia lunata (Wakk.) Boedijn”
Claim · model-written summary
Wound- or nodal-inoculation of stem pieces of four cassava cultivars with C. lunata mycelial plugs produced lesions and bud necrosis similar to field symptoms on all inoculated plants within 1 month, while control plants stayed symptom-free.
- Taxon
- CassavaManihot esculentat0
- Treatment
- inoculatede0
- Interactor
- Curvularia lunataCurvularia lunatat1pathogen
- Outcome
- lesions and bud necrosise0
- Qualifier
- within 1 monthe0
- Comparator
- Control plantse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
t1“Curvularia lunata”
e0“Control plants remained symptom-free whereas lesions and bud necrosis similar to field symptoms were observed on all inoculated plants within 1 month”
Claim · model-written summary
Symptom development after inoculation was quicker (2 to 3 weeks) on wound-inoculated cassava stems than on nonwounded stems.
- Taxon
- CassavaManihot esculentat0
- Treatment
- wound-inoculatede0
- Interactor
- Curvularia lunataCurvularia lunatat1pathogen
- Outcome
- Symptom developmente0
- Direction
- quickere0
- Value
- 2 to 3 weekse0
- Comparator
- nonwounded stemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
t1“Curvularia lunata”
e0“Symptom development was quicker (2 to 3 weeks) on wound-inoculated than on nonwounded stems”
Claim · model-written summary
Mortality of artificially wound-inoculated cassava buds ranged between 30 and 100%, depending on genotype and manner of inoculation.
- Taxon
- CassavaManihot esculentat0
- Interactor
- Curvularia lunataCurvularia lunatat1pathogen
- Outcome
- Mortality of artificially wound-inoculated budse0
- Value
- between 30 and 100%e0
- Qualifier
- depending on genotype and manner of inoculatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
t1“Curvularia lunata”
e0“Mortality of artificially wound-inoculated buds ranged between 30 and 100%, depending on genotype and manner of inoculation”
Claim · model-written summary
Artificially infected cassava stem and bud portions plated on PDA consistently yielded C. lunata.
- Taxon
- CassavaManihot esculentat0
- Interactor
- C. lunataCurvularia lunatae0pathogen
- Outcome
- consistently yielded C. lunatae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“Artificially infected stem and bud portions plated on PDA consistently yielded C. lunata”
Claim · model-written summary
When cassava buds were completely colonized, sprouting was completely inhibited.
- Taxon
- CassavaManihot esculentat0
- Organ / stage
- budse0
- Outcome
- sproutinge0
- Direction
- completely inhibitede0
- Qualifier
- completely colonizede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“When buds were completely colonized, sprouting was completely inhibited”
Claim · model-written summary
Partially colonized cassava buds sprouted, but growth was reduced by 20 to 50% (depending on genotype) compared with healthy stems.
- Taxon
- CassavaManihot esculentat0
- Organ / stage
- budse0
- Outcome
- growthe0
- Direction
- reducede0
- Value
- 20 to 50%e0
- Qualifier
- depending on genotypee0
- Comparator
- healthy stemse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Cassava”
e0“partially colonized buds sprouted, but growth was reduced by 20 to 50% (depending on genotype), compared with healthy stems”
Claim · model-written summary
This is reported as the first report of C. lunata being pathogenic on cassava.
- Taxon
- cassavaManihot esculentae0
- Interactor
- C. lunataCurvularia lunatae0pathogen
- Outcome
- first report of C. lunata pathogenice0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is the first report of C. lunata pathogenic on cassava”
The same questions in other papers
inoculation · Curvularia lunata · Manihot esculenta (cassava)Results agree
1 paper in the same direction as this paper
- negative
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.