Identification of Fusarium cugenangense as a causal agent of wilt disease on Pyrus pyrifolia in China

In recent years, an unusual wilt disease affecting Pyrus pyrifolia has been observed in various regions of Jiangsu, China. This disease originates from the roots and progresses with distinctive browning patterns along vascular tissues, even extending over two meters above the ground. These symptoms set it apart from recognized pear diseases and typically lead to the death of affected trees within the same or the following year. Furthermore, this disease exhibits a tendency to spread to neighboring trees even after the removal of affected trees, presenting a substantial threat to pear production. To ascertain the causative agent, the present study encompassed pathogen isolation, morphological and molecular identification, as well as validation experiments adhering to Koch's postulates. The fungal isolates obtained were identified as Fusarium cugenangense based on characteristics of the colonies and conidia, in addition to a phylogenetic analysis using DNA sequences of the translation elongation factor 1-alpha (tef1), calmodulin (CaM), and RNA polymerase second largest subunit (rpb2) genes. Pathogenicity of the isolated F. cugenangense on pear was confirmed by artificial inoculation. By introducing GFP-labeled pathogens into the roots, colonization in stem and leaf tissues was observed via fluorescence microscopy and transmission electron microscopy. Furthermore, these pathogens were successfully reisolated from stems and foliage, conclusively providing evidence of systemic infection within the pear plants. To the best of our knowledge, this is the first report of F. cugenangense causing pear wilt disease in China.