New Leaf Spot Disease Found on Dandelion Plants

Greg Howard
21st January, 2024

New Leaf Spot Disease Found on Dandelion Plants

Image Source: Natural Science News, 2024

Taraxacum mongolicum, a plant in the daisy family known for its edible and medicinal properties, is commonly grown across China. Recently, an issue arose with these plants in Tianjiazhai Town, Xining City, Qinghai Province. The plants were found to have round or irregular brown spots, occasionally with gray centers, on their leaves. This issue was widespread, affecting 15%-30% of the area observed, which could significantly impact both the plant quality and yield. To identify the cause, researchers collected samples from plants showing these leaf spots. In a controlled lab environment, they isolated pieces of the leaves that were both healthy and infected. These leaf samples were disinfected and placed on water agar plates to promote fungal growth. After two days, telltale signs of fungal infestation—such as spore-producing structures called conidiophores and conidia—were visible. A total of 11 fungal isolates were identified from the samples. When cultured on a potato-based growth medium, the fungi produced dark grey to black brown mycelia (the vegetative part of a fungus) and dark conidia (fungal spores) with multiple compartments called septa. The spores were quite large, with distinct beaks, which are elongation at one end of the spore, characteristic of certain fungi. For precise identification, researchers used a range of genetic markers from different regions of the fungal DNA—including the internal transcribed spacer of ribosomal DNA, and genes for important cell functions—then compared them to known sequences in a database. The analysis showed that these isolates were very similar to a known pathogen, Alternaria solani, which is infamous for causing early blight in potato and other related crops. Additionally, to confirm that these isolates were truly responsible for the leaf spots on T. mongolicum, the research team conducted a series of experiments following Koch's postulates, a classical set of criteria for establishing the cause of a disease. Healthy T. mongolicum seedlings were deliberately infected with fungal isolates, which resulted in leaf spot symptoms identical to those found in the field. Furthermore, the fungus could be re-isolated from the infected plants, fulfilling Koch's postulates and confirming the culprit of the leaf spot disease. This is the first time A. solani has been reported to cause leaf spot disease in T. mongolicum in China. The researchers suggest that this disease should be considered when developing management practices aimed at protecting these plants. This study provides crucial knowledge for preventing and managing leaf spot disease in T. mongolicum.

EnvironmentBiochemPlant Science

References

Main Study

1) First Report of Leaf Spot on Taraxacum mongolicum Caused by Alternaria solani in China.

Published 19th January, 2024

https://doi.org/10.1094/PDIS-08-23-1538-PDN


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