Identification of Pathogens Causing Anthracnose on King Oranges (Citrus nobilis var. Typica Hassk)

<b>Background and Objective:</b> Anthracnose is one of the main causes seriously affecting the fruit yield and quality of king oranges. This study aimed to identify the fungal pathogen <i>Colletotrichum gloeosporioides</i> causing anthracnose on king oranges in Vinh Long. <b>Materials and Methods:</b> Fruits with diseases were collected from the king orange garden located in Vinh Long in September, 2020. Firstly, symptoms of infected fruits were observed and recorded. Next, pathogens were isolated from these fruits and then tested using the Koch procedure. Specifically, the isolated strains of fungi were identified based on their morphological traits and ITS sequences on rRNA amplified by a pair of primers ITS1/ITS4. <b>Results:</b> A pure culture of the identified fungus was later artificially inoculated into healthy fruits for 1 week to confirm its pathogenicity. The fungal spores were cylindrical, rounded or obtuse at 2 ends, 12.8-16.4 mm in length and 3.47-5.27 mm in width. The ITS sequence of <i>Colletotrichum</i> causing anthracnose on king oranges had similar to the following sequences found on the Genbank with percent identities ranging from 97.93-98.29%. In the ITS sequence, the composition of GC was higher than that of AT, with 52.72% against 47.28%, respectively. The results of phylogeny demonstrated that the genetic sequence of the fungus causing anthracnose on king oranges had a close relationship with that of other species of <i>Colletotrichum </i>found on NCBI. <b>Conclusion:</b> The findings show that <i>Colletotrichum gloeosporioides</i>, a type of fungi, was the cause of anthracnose in king orange grown in Vinh Long province.