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Study on Pathogenesis of Cytospora pyri in Korla Fragrant Pear Trees (Pyrus sinkiangensis)

Summary

Researchers identified Cytospora pyri as the fungus causing a serious canker disease in Korla fragrant pear trees grown in Xinjiang, China. The fungus cannot directly infect healthy bark but requires wounds to enter trees, then spreads rapidly through tissues using powerful cell-degrading enzymes. Understanding these infection mechanisms can help farmers prevent the disease by protecting trees from injuries and maintaining tree health.

Background

Pear Valsa cankers caused by Cytospora species are destructive fungal diseases affecting Korla fragrant pear orchards in Xinjiang, China. Previous identification of canker pathogens has been inconsistent due to reliance on morphology alone or single-gene analysis. Understanding the pathogenesis mechanisms of these pathogens is essential for developing effective control strategies.

Objective

To identify the pathogenic fungus causing Valsa cankers in Korla fragrant pear trees using morphological and multigene sequence analyses, determine optimal growth conditions, and elucidate the infection process and pathogenic mechanisms of the identified pathogen.

Results

The pathogenic fungus was identified as Cytospora pyri with 99.83% ITS sequence homology. Optimal growth occurred at 28°C, pH 5, with glucose and peptone as preferred carbon and nitrogen sources. C. pyri conidia could not directly penetrate intact bark but required wounds for invasion. Fungal hyphae initially spread intercellularly, then penetrated cell walls and proliferated within host tissues, reaching the xylem by 10 days. Pycnidia formed after 15-20 days with visible yellow waxy gums. Polygalacturonase (PG) activity was seven times higher in infected tissue than controls.

Conclusion

C. pyri was confirmed as the causal agent of Valsa cankers in Korla fragrant pear trees. The pathogen requires wounds for infection and proliferates rapidly within host tissues through coordinated secretion of cell wall-degrading enzymes, particularly polygalacturonase. Control strategies should focus on preventing mechanical injuries and enhancing tree vigor to reduce susceptibility to infection.
  • Published in:Journal of Fungi,
  • Study Type:Laboratory Research Study,
  • Source: 10.3390/jof11040257, PMID: 40278078
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