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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 new, faster way to test poplar trees for resistance to stem canker diseases by inoculating fungal pathogens directly onto leaves instead of using whole stem segments. This method is much simpler, cheaper, and produces results in just 5 days compared to weeks for traditional methods. By testing leaves at different positions on trees and under different light conditions, researchers showed this leaf-based method accurately identifies resistant poplar clones for breeding programs.

Background

Hybrid breeding is an efficient strategy for disease control in tree species, but current selection methods for resistant clones are limited by the in vitro stem segment inoculation method, which is constrained by availability of inoculating materials and cannot rapidly and cost-effectively screen all hybrid clones. Stem canker pathogens such as Valsa sordida and Botryosphaeria dothidea are major contributors to forest diseases in poplar plantations.

Objective

To develop and validate a novel in vivo leaf inoculation method for rapidly and efficiently assessing resistance to stem canker pathogens in poplar hybrid clones. The study aims to evaluate how leaf developmental stage, light conditions, and fungal culture duration affect pathogen-induced disease symptoms and to compare the effectiveness of this method with conventional stem segment inoculation.

Results

The leaf inoculation method successfully induced necrotic lesions and fungal structures on poplar leaves within 5 days. Upper leaves (5-7th) showed higher resistance than lower leaves (18-20th); shading increased disease severity; and 4-day-cultured mycelium induced more severe symptoms than 7-day-cultured mycelium. The 48 poplar clones were divided into seven resistance groups, and results were consistent between leaf and stem inoculation methods (R² values of 0.52-0.84).

Conclusion

The in vivo leaf inoculation method is rapid, efficient, and cost-effective for assessing poplar resistance to stem canker pathogens with abundant inoculation materials and minimal adverse effects on host plants. This method is particularly suitable for large-scale resistance screening in poplar breeding progeny and early seedling selection, representing a significant advancement for tree pathology and disease resistance breeding programs.
  • Published in:Plant Methods,
  • Study Type:Experimental Study,
  • Source: 10.1186/s13007-025-01360-1, PMID: 40128764
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