Abstract
Chinese olive (Canarium album) is a well-known plant used both as food and medicine, extensively cultivated in southern China (Kuo et al., 2016). Its production is challenged by various fungal diseases. From July to October 2023, Chinese olive plants in an approximately 400 hectare conventional hillside orchard in Chaozhou, Guangdong province, China (23°39'45.36″N, 116°37'45.48″E), where sustainable Chinese olive farming has been practiced for over a decade, exhibited leaf blotch symptoms with a disease incidence of 40% (n = 100 plants investigated). Symptoms include yellow or brown leaf blotches, followed by drying, curling, and eventual leaf drop. To identify the causal agent, seven symptomatic leaves from seven trees were collected. The symptomatic leaves were cut into pieces of about 0.3 mm2 at the necrotic lesion edges and surface disinfected. The pieces were placed on potato dextrose agar (PDA), incubated in the dark at 28°C for 5 days, then subcultured for 7 days. Four fungal isolates were obtained with an isolation frequency of 57%. Genomic DNA was extracted from the isolates. Morphological analysis and internal transcribed spacer (ITS) region sequencing revealed no observable differences among isolates. The representative isolate (LB-1) cultured on PDA was initially white, turning light grey with dense aerial mycelium after 7 days. The transparent hyphae displayed intricate branching patterns and multiple cellular structures. The conidia were single-celled, hyaline, fusiform structures measuring 3.6-7.8 × 1.17-2.83 μm (n = 50). Morphologically, the fungal isolates resembled Phyllosticta capitalensis (Wikee et al. 2013). Primers ITS1/ITS5, ACT-512F/ACT-783R, and EF1/EF2 were used to amplify the ITS region, the actin (ACT) gene, and the transcription elongation factor (TEF), respectively (Wang et al. 2023). The sequences obtained from the LB-1 isolate have been deposited in NCBI GenBank (accession nos. PP922193; PP960207 and PP960206). A phylogenetic tree was constructed based on aligned sequences (Wang et al. 2023). BLAST analysis showed LB-1 isolate shares 99.4%-100% similarity with sequences KY855645, KY855590, and KY855919 from P. capitalensis CPC27084. Based on morphological and molecular analysis, isolate LB-1 was identified as P. capitalensis. Pathogenicity assays of the LB-1 isolate were conducted on 2-year-old Canarium album seedlings. A 10⁶ spores/mL LB-1 suspension was applied to 3 mm spots on the leaves of four plants for inoculation. Controls leaves was treated with sterile water. The inoculated plants were placed in a greenhouse at 28°C with 80% humidity. The experiment was repeated 3 times. Leaves inoculated with LB-1 isolates showed blotch symptoms similar to those in the field, the controls remained healthy. Reisolation of P. capitalensis was performed confirmed by morphology and DNA sequencing, fulfilling Koch's postulates. Previous studies have shown that P. capitalensis causes fungal diseases on fruit trees such as Citrus lalifolia and Mangifera indica (Wikee et al. 2013). To our knowledge, this is the first report of Phyllosticta capitalensis causing leaf blotch on Chinese olive in China. Preliminary observations suggest it may be present in other olive-producing regions of Guangdong. It causes significant leaf wilting and shedding, potentially reduces fruit quality, and lowers overall yield. This discovery will offer valuable insights for creating effective control measures against this recently emerged severe disease.
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Claims 14
Claim · model-written summary
Chinese olive orchard plants had 40% leaf blotch incidence.
Verbatim
e0“Chinese olive plants in an approximately 400 hectare conventional hillside orchard in Chaozhou, Guangdong province, China (23°39'45.36″N, 116°37'45.48″E), where sustainable Chinese olive farming has been practiced for over a decade, exhibited leaf blotch symptoms with a disease incidence of 40%”
Claim · model-written summary
Symptoms included blotches followed by drying, curling, and leaf drop.
- Taxon
- Chinese olive (Canarium album)
Canarium albumt0 - Outcome
- yellow or brown leaf blotches, followed by drying, curling, and eventual leaf drope0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Symptoms include yellow or brown leaf blotches, followed by drying, curling, and eventual leaf drop”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
Four fungal isolates were obtained at a 57% isolation frequency.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- fungal isolatese0
- Value
- 57%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Four fungal isolates were obtained with an isolation frequency of 57%”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The isolates had no observable morphological or ITS differences.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- no observable differences among isolatese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Morphological analysis and internal transcribed spacer (ITS) region sequencing revealed no observable differences among isolates”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The fungal isolates resembled Phyllosticta capitalensis morphologically.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Interactor
- Phyllosticta capitalensisPhyllosticta capitalensise0pathogen
- Outcome
- resembled Phyllosticta capitalensise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Morphologically, the fungal isolates resembled Phyllosticta capitalensis”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
LB-1 sequence similarity to P. capitalensis CPC27084 was 99.4%-100%.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Interactor
- P. capitalensisPhyllosticta capitalensise0pathogen
- Outcome
- similaritye0
- Value
- 99.4%-100%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LB-1 isolate shares 99.4%-100% similarity with sequences KY855645, KY855590, and KY855919 from P. capitalensis CPC27084”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
Isolate LB-1 was identified as P. capitalensis.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Interactor
- P. capitalensisPhyllosticta capitalensise0pathogen
- Outcome
- identified as P. capitalensise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“isolate LB-1 was identified as P. capitalensis”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
LB-1 inoculation caused leaf blotch while controls remained healthy.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Treatment
- inoculated with LB-1 isolatese0
- Interactor
- LB-1 isolatese0pathogen
- Outcome
- blotch symptomse0
- Comparator
- controlse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaves inoculated with LB-1 isolates showed blotch symptoms similar to those in the field, the controls remained healthy”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
P. capitalensis was reisolated, fulfilling Koch’s postulates.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Interactor
- P. capitalensisPhyllosticta capitalensise0pathogen
- Outcome
- Reisolation of P. capitalensise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reisolation of P. capitalensis was performed confirmed by morphology and DNA sequencing, fulfilling Koch's postulates”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The authors report P. capitalensis causing Chinese olive leaf blotch in China for the first time.
- Taxon
- Chinese olivee0
- Interactor
- Phyllosticta capitalensisPhyllosticta capitalensise0pathogen
- Outcome
- causing leaf blotche0
- Setting
- Chinae0
Verbatim
e0“this is the first report of Phyllosticta capitalensis causing leaf blotch on Chinese olive in China”
Claim · model-written summary
Preliminary observations suggest the pathogen occurs in other Guangdong olive-producing regions.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- may be presente0
- Qualifier
- Preliminary observationse0
- Setting
- Guangdonge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Preliminary observations suggest it may be present in other olive-producing regions of Guangdong”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The disease causes leaf wilting and shedding.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- leaf wilting and sheddinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It causes significant leaf wilting and shedding”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The disease potentially reduces fruit quality.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- fruit qualitye0
- Direction
- reducese0
- Qualifier
- potentiallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“potentially reduces fruit quality”
t0“Chinese olive (Canarium album)”
Claim · model-written summary
The disease potentially lowers yield.
- Taxon
- Chinese olive (Canarium album)Canarium albumt0
- Outcome
- overall yielde0
- Direction
- lowerse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lowers overall yield”
t0“Chinese olive (Canarium album)”