Insect infestations cause substantial changes in the leaves they attack, but the effects of insect infestation on photosynthesis and gene expression in the whole infestation period are rarely reported. In this study, the effects of poplar aphid (Chaitophorus populialbae Boyer de Fonscoloube) on photosynthetic rate and gene expression of Populus alba var. pyramidalis were studied, from 2 to 36 days after low-density aphid inoculation (DAI). The results revealed a dynamic change of photosynthesis in poplar after aphid infestation: compensatory increased at 8 DAI, was inhibited at 17 DAI, but repaired after 21 DAI. Aphid infestation promoted the expression of the majority of differentially expressed genes (DEGs) at 4, 6, 8, and 21 DAI. The DEGs were enriched into a plant–pathogen interaction, plant hormone signal transduction, and MAPK signaling pathway, suggesting a significant but transient resistance to disease or other stresses. Photosynthesis-related DEGs were downregulated at 8 DAI, which might result in photosynthetic inhibition at 17 DAI. The expression of flavonoid biosynthesis-related DEGs dynamic changed from all downregulated at 2 DAI to almost all upregulated at 21 DAI, suggesting a persistent resistance to insect infestation. This study reveals dynamic changes in photosynthesis, resistance to pathogens, and insects in poplar leaves after aphid infestation.

A key step in the study of tree pathology is the identification of an appropriate method for inoculating pathogens of diseases in branches and trunks. Pathogens of diseases in branches and trunks are commonly inoculated through punching, burning, and toothpick inoculation. However, there is a lack of comparative analyses of the inoculation outcomes of these three methods. In this work, six-year-old P. alba var. pyramidalis were inoculated with V. sordida using punching, burning, and toothpick techniques to investigate the differences in the effectiveness of these inoculation methods. Results reveal that the incidence rate was 93.55% in the toothpick inoculation group, significantly higher than the 80.65% in the burning inoculation group (chi-square, n = 90, p = 0.007), while punching inoculation exhibited significant pathological responses in the early stages, with spontaneous healing in the later stage. Additionally, toothpick inoculation was more efficient in inducing Valsa canker when inoculating the pathogen at the bottom of the tree, with lower intra- and inter-row spacing (stand density) providing better outcomes than higher intra- and inter-row spacing. The results of this study demonstrate that toothpick inoculation is an optimal option for studying the artificial inoculation of V. sordida in six-year-old P. alba var. pyramidalis, providing technical support for research on poplar diseases and offering a theoretical basis for the inoculation of other diseases in the branch and trunk.

A key step in the study of tree pathology is the identification of appropriate method for inoculating pathogens of diseases in branch and trunk. Pathogens of diseases in branch and trunk are commonly inoculated through punching, burning, and toothpick inoculation. However, there is a lack of comparative analysis of the inoculation outcomes of these three methods. In this work, Six‐year‐old P. alba var. pyramidalis were inoculated with V. sordida, using punching, burning, and toothpick techniques, respectively, to investigate the differences in the effectiveness of these inoculation methods. Results reveal that the incidence rate was 93.55% in the toothpick inoculation group, significantly higher than 80.65% in the burning inoculation group (p = 0.007), while punching inoculation exhibited significant pathological responses in the early stages, with spontaneous healing in the later stage. Addi-tionally, toothpick inoculation was more efficient in inducing Valsa canker when inoculating the pathogen at the bottom of the tree, with lower intra‐ and inter‐row spacing (stand density) providing better outcomes than higher intra‐ and inter‐row spacing. The results of this study demonstrate that toothpick inoculation is an optimal option for studying the artificial inoculation of V. sordida in six‐year‐old P. alba var. pyramidalis, providing technical support for research on poplar diseases and offering a theoretical basis for the inoculation of other diseases in branch and trunk.

Valsa sordida and Botryosphaeria dothidea are two crucial necrotrophic fungal pathogens that damage many plant hosts, particularly species in the genus Populus. These two fungal pathogens occur mainly in poplar branches, stems, and twigs, causing classic symptoms such as canker lesions, canopy dieback, and wilting. Pathogen inoculation is the most efficient pathway to study the mechanism of plant disease. Besides the canker lesions around the inoculation sites on the stems, a novel developmental phenomenon, copious adventitious roots (ARs) with bright red color, were observed in poplar species after stem canker pathogen inoculations. In this study, we described the method for inducing ARs using fungal pathogens in poplar trees. The crucial step of this method is the pathogen inoculation after (phloem or epidermis) girdling manipulation. The second crucial step is the application of the moisturizing material. Compared to the moisturizing manipulation with Parafilm, wrapping the inoculated sites with household polyethylene (PE) plastic wrap can produce colorful, numerous, and robust ARs in 20 days after girdling-inoculation. Finally, white ARs sprouted from the inoculated rings in the poplar stems after shading treatment (wrapping the stems with aluminum foil). This method introduces a novel experimental system for studying root development and morphogenesis, which is crucial for understanding the biology of root development, morphogenesis, and response under disease stress. Furthermore, when combined with shading treatment, this study can provide a convenient experimental system for investigating light response-related processes, for example, the biosynthesis of flavonoids, anthocyanins, or other related metabolites, and genes or transcription factors involved in these processes.

Calonectria leaf blight is one of the most destructive diseases affecting Eucalyptus plantations worldwide. Although Guangxi holds the largest area of Eucalyptus plantations in China, the species diversity and geographic distribution of Calonectria associated with this disease remain poorly understood. To address this gap, a systematic field survey was carried out across 19 Eucalyptus plantations in Guangxi in 2025, planted with E. urophylla × E. grandis or other commercial hybrids. A total of 497 Calonectria isolates were obtained from symptomatic plant tissues, and eight species belonging to three species complexes were identified based on multi-locus phylogenetic analyses. These included C. queenslandica (83.3%), C. pseudoreteaudii (9.7%), C. reteaudii (4.6%) in the C. reteaudii species complex, C. aciculata (0.2%), C. eucalypti (0.8%), C. honghensis (0.2%) in the C. colhounii species complex, C. hongkongensis (0.8%), C. ilicicola (0.4%) in the C. kyotensis species complex. Calonectria species composition varied among the three studied clusters, with seven species detected in the West, three in the South and two in the East. Calonectria queenslandica was present and dominant in all three clusters, indicating that it is the main causal agent of Calonectria leaf blight outbreaks across the province. MaxEnt modeling identified annual mean temperature (Bio1, contribution 66.8%) as the most influential bioclimatic variable associated with the predicted distribution of C. queenslandica, with high suitability habitats concentrated in central-southern Guangxi, central-eastern Guangdong, and southern Fujian. Precipitation of warmest quarter contributed 12.2% but had zero permutation importance, indicating no independent effect, though rainfall and humidity may still influence disease development. Pathogenicity tests confirmed that all species were pathogenic on E. urophylla × E. tereticornis trees, with significant variation in aggressiveness both between and within species. This study provides a comprehensive assessment of Calonectria diversity and distribution in Guangxi Eucalyptus plantations. The findings extend the known geographic ranges of Calonectria and offer a scientific basis for developing sustainable management strategies for the disease.

Valsa sordida and Botryosphaeria dothidea are two crucial necrotrophic fungal pathogens that damage many plant hosts, particularly species in the genus Populus. These two fungal pathogens occur mainly in poplar branches, stems, and twigs, causing classic symptoms such as canker lesions, canopy dieback, and wilting. Pathogen inoculation is the most efficient pathway to study the mechanism of plant disease. Besides the canker lesions around the inoculation sites on the stems, a novel developmental phenomenon, copious adventitious roots (ARs) with bright red color, were observed in poplar species after stem canker pathogen inoculations. In this study, we described the method for inducing ARs using fungal pathogens in poplar trees. The crucial step of this method is the pathogen inoculation after (phloem or epidermis) girdling manipulation. The second crucial step is the application of the moisturizing material. Compared to the moisturizing manipulation with Parafilm, wrapping the inoculated sites with household polyethylene (PE) plastic wrap can produce colorful, numerous, and robust ARs in 20 days after girdling-inoculation. Finally, white ARs sprouted from the inoculated rings in the poplar stems after shading treatment (wrapping the stems with aluminum foil). This method introduces a novel experimental system for studying root development and morphogenesis, which is crucial for understanding the biology of root development, morphogenesis, and response under disease stress. Furthermore, when combined with shading treatment, this study can provide a convenient experimental system for investigating light response-related processes, for example, the biosynthesis of flavonoids, anthocyanins, or other related metabolites, and genes or transcription factors involved in these processes.