A rapid and efficientin vivoinoculation method for introducing tree stem canker pathogens onto leaves: Suitable for large-scale assessment of resistance in poplar breeding progeny

Abstract

Hybrid breeding is the most direct and efficient method of controlling and managing tree diseases. However, "in vitro stem inoculation" can not be used for rapid, efficient, and low-cost screening of resistant clones in the early stage of stem canker infection. Therefore, we inoculated stem canker pathogens on poplar leaves to evaluate the resistance of hybrid clones in the poplar-Valsa sordidapathosystem. "In vivo leaf inoculation" showed that: 1)V. sordidainduces extended necrotic lesions and conidia on leaves. 2) The upper leaves exhibited higher resistance than the middle leaves. 3) The shading conditions induced more severe symptoms on leaves than the lighting conditions. 4) The susceptibility of poplar leaves to juvenile mycelium was higher than old mycelium’s. 5) The resistance of 48 poplar clones againstV. sordidawas distributed normally. 6) The efficacy of "in vivo leaf inoculation" was consistent with "in vitro stem inoculation". In summary, "in vivo leaf inoculation" has the advantages of a wide application range, simple operation, short experimental process, and host safety. This method is of great significance for poplar breeding, the study of pathology and molecular biology, pathogenic differentiation, and sporulation of fungal canker pathogens.