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A rapid and efficient in vivo inoculation method for introducing tree stem canker pathogens onto leaves: suitable for large-scale assessment of resistance in poplar breeding progeny

Summary

Scientists developed a faster and easier way to test whether poplar trees are resistant to stem canker diseases caused by fungi. Instead of using traditional time-consuming stem tests, they inoculate fungal pathogens directly onto leaves, which shows results in just 5 days. This new leaf-based method uses abundant, readily available leaf tissue and can test many poplar breeding candidates quickly and cheaply, making it ideal for developing disease-resistant poplar varieties.

Background

Poplar species are susceptible to stem canker pathogens including Valsa sordida and Botryosphaeria dothidea, which cause significant forest diseases. Current resistance screening methods using in vitro stem segment inoculation are time-consuming, space-intensive, and costly, limiting the efficiency of hybrid breeding programs for disease-resistant poplar clones.

Objective

To develop and validate a rapid, efficient in vivo leaf inoculation method for assessing resistance to stem canker pathogens in poplar breeding progeny. The study evaluates the impact of leaf developmental stage, light conditions, and fungal culture age on pathogen-induced symptoms and validates the method against traditional stem segment inoculation.

Results

The leaf inoculation method successfully induced necrotic lesions and pycnidial structures within 5 days. Upper (5-7th) leaves showed higher resistance than lower (18-20th) leaves; shaded leaves were more susceptible than light-exposed leaves; and 4-day-cultured mycelium showed higher pathogenicity than 7-day-cultured. Resistance rankings from leaf inoculation were consistent with stem segment inoculation results (R² = 0.52-0.84).

Conclusion

The in vivo leaf inoculation method is a rapid, cost-effective alternative to stem segment inoculation for assessing poplar resistance to stem canker pathogens. It enables large-scale screening of hybrid breeding progeny, requires minimal plant material, has rapid disease onset, and shows consistency with traditional methods. This method is particularly suitable for seedling-stage phenotypic selection in poplar breeding programs.
  • Published in:Plant Methods,
  • Study Type:Experimental validation study,
  • Source: 10.1186/s13007-025-01360-1, PMID: 40128764, PMCID: PMC11934469
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