Abstract
Catalpa bungei originates from China. It is fast-growing and possesses a vertically aligned trunk, rendering it a commendable construction material and a significant economic species. In July 2022, a serious leaf spot occurred in the LanLake farm (surveyed area of about 700 acres) in Nanyang (33°3'23" N, 112°28'50" E), Henan Province, China. The incidence rate of leaf disease reached 54% (n=100). The disease initially manifested as irregular round spots with a yellowish-brown hue, subsequently extending in all directions. Later, the lesion periphery exhibited a darkening effect, leading to yellowing. Twenty diseased leaves were randomly collected and cut into small pieces at the interfaces between infected and healthy tissues. The tissues were sterilized in a solution of 75% ethanol and 1% NaClO for 30 seconds and 1 minute, respectively. After rinsing in sterile water, the pieces were placed on potato dextrose agar (PDA) plates and incubated at 25°C for 5 days. A total of 29 purified fungal strains were acquired, exhibiting comparable phenotypes in terms of morphological characteristics. Three strains (QS1-1, QS1-2, and QS1-3) were isolated for subsequent investigations. The colony exhibited abundant aerial mycelium with shades ranging from dark green to grey-brown on the reverse side. To analyze the morphological characteristics of conidia, potato carrot agar (PCA) was used as the culture medium and incubated at 25°C with a 12-hour light/dark cycle. Conidia were obclavate or spheroidal, dark brown, with 3 to 5 transverse septa, and 1 to 4 longitudinal septa, measuring 12.4 to 36.7 × 4.4 to 9.0 μm (n=100), with conical beak lengths ranging from 0 to 4.3 μm. These morphological traits suggested that the pathogen shares similarities with the Alternaria species. The rDNA internal transcribed spacer (ITS), translation elongation factor 1-alpha gene (tef1), glyceraldehyde 3-phosphate dehydrogenase gene (gapdh), and RNA polymerase II second largest subunit (rpb2) were amplified for further molecular identification. The resultant sequences were submitted to GenBank with the following accession numbers: OR733559, OR742124, OR761873 (ITS), OR939796, OR939797, OR939798 (tef1), OR939801, OR939802, OR939803 (gapdh), and PP054846, PP054847, PP054848 (rpb2). A Phylogenetic tree was constructed of combined genes (ITS, tef1, gapdh, and rpb2) of sequences, alongside the sequences of the type strains by the neighbor-joining method. The three strains formed a clade with the strains CBS 121456 of Alternaria alternata in phylogenetic trees, being separated from other Alternaria spp. The morphological features and molecular analyses supported the strains as members of Alternaria alternata (Woudenberg et al. 2015). To validate pathogenicity, a conidial suspension (106 conidia ml-1) of all three strains was inoculated onto three healthy leaves of five seedlings, with 50 μl of inoculum absorbed with cotton balls. Another group of five plants received sterile water as a control. All plants were incubated in a climate chamber at 28°C and 90% relative humidity. Four days post-inoculation, lesions resembling natural phenomena were observed, whereas control plants showed no symptoms. Subsequent reisolation produced cultures that were morphologically and molecularly identical to the original strains, fulfilling Koch's postulates. Stem canker of C. bungei caused by Phytophthora nicotianae has been reported in China (Chang et al. 2022). This is the first report of A. alternata causing leaf spots on C. bungei in China. Further research is required on management options to control this disease and the host range still needs to be clarified for accurate disease management.
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Claims 8
Claim · model-written summary
Catalpa bungei leaf disease incidence reached 54% at the surveyed farm in Nanyang.
- Taxon
- Catalpa bungei
Catalpa bungeit0 - Outcome
- incidence rate of leaf diseasee0
- Direction
- reachede0
- Value
- 54%e0
- Setting
- LanLake farme1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The incidence rate of leaf disease reached 54% (n=100)”
e1“in the LanLake farm (surveyed area of about 700 acres) in Nanyang (33°3'23" N, 112°28'50" E), Henan Province, China”
t0“Catalpa bungei”
Claim · model-written summary
Leaf spot on Catalpa bungei began as irregular yellowish-brown round spots and later developed dark lesion edges and yellowing.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Outcome
- irregular round spots with a yellowish-brown huee0
- Qualifier
- leading to yellowinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The disease initially manifested as irregular round spots with a yellowish-brown hue, subsequently extending in all directions. Later, the lesion periphery exhibited a darkening effect, leading to yellowing”
t0“Catalpa bungei”
Claim · model-written summary
Twenty diseased Catalpa bungei leaves yielded 29 phenotypically similar purified fungal strains.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Outcome
- purified fungal strainse0
- Value
- 29e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A total of 29 purified fungal strains were acquired, exhibiting comparable phenotypes in terms of morphological characteristics”
t0“Catalpa bungei”
Claim · model-written summary
Three fungal strains from Catalpa bungei leaf spots clustered with Alternaria alternata strain CBS 121456.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Interactor
- Alternaria alternata
.jpg?width=60)
Alternaria alternatae0pathogen - Outcome
- formed a clade with the strains CBS 121456 of Alternaria alternatae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“The three strains formed a clade with the strains CBS 121456 of Alternaria alternata in phylogenetic trees, being separated from other Alternaria spp.”
t0“Catalpa bungei”
Claim · model-written summary
Morphology and molecular analysis identified the Catalpa bungei leaf spot isolates as Alternaria alternata.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Interactor
- Alternaria alternataAlternaria alternatae0pathogen
- Outcome
- strains as members of Alternaria alternatae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The morphological features and molecular analyses supported the strains as members of Alternaria alternata”
t0“Catalpa bungei”
Claim · model-written summary
Inoculation with the three Alternaria alternata isolates caused natural-looking lesions on Catalpa bungei seedlings after four days, while water controls showed no symptoms.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Treatment
- a conidial suspension (106 conidia ml-1) of all three strainse0
- Interactor
- Alternaria alternataAlternaria alternatat0pathogen
- Outcome
- lesions resembling natural phenomenae2
- Qualifier
- Four days post-inoculatione2
- Comparator
- sterile watere1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a conidial suspension (106 conidia ml-1) of all three strains was inoculated onto three healthy leaves of five seedlings”
e1“Another group of five plants received sterile water as a control”
e2“Four days post-inoculation, lesions resembling natural phenomena were observed, whereas control plants showed no symptoms”
t0“Alternaria alternata Causing Leaf Spot on Catalpa bungei”
Claim · model-written summary
The inoculated Catalpa bungei seedlings yielded reisolated cultures identical to the original strains.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Outcome
- cultures that were morphologically and molecularly identical to the original strainse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Subsequent reisolation produced cultures that were morphologically and molecularly identical to the original strains, fulfilling Koch's postulates”
t0“Catalpa bungei”
Claim · model-written summary
The authors report Alternaria alternata causing Catalpa bungei leaf spots in China for the first time.
- Taxon
- Catalpa bungeiCatalpa bungeit0
- Interactor
- A. alternataAlternaria alternatae0pathogen
- Outcome
- first report of A. alternata causing leaf spots on C. bungeie0
- Setting
- Chinae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is the first report of A. alternata causing leaf spots on C. bungei in China”
t0“Alternaria alternata Causing Leaf Spot on Catalpa bungei”