Identification and potential of the hyperparasite Acremonium persicinum as biocontrol agent against coffee leaf rust.

Coffee leaf rust (CLR) caused by Hemileia vastatrix, has emerged as a growing threat to coffee production in China. This study focused on the identification and characterization of the hyperparasitic fungus Acremonium persicinum using integrated plant pathology and molecular biology approaches. The spore suspension of the fungal strain HY85 exhibited a 91.18% inhibition rate against the germination of H. vastatrix urediniospores. Inoculation of coffee leaf discs with H. vastatrix urediniospores resulted in the development of visible chlorotic lesions after 16 days. However, other inoculation methods did not yield early chlorotic lesions, indicating an absence of H. vastatrix infection. Quantitative PCR analysis revealed that the copy numbers of H. vastatrix DNA after 16 days postinoculation were 1.41 × 108, 7.59 × 108, and 1.66 × 108, respectively. Notably, H. vastatrix DNA was undetectable in leaf discs coinoculated with H. vastatrix urediniospores and the hyperparasitic strain HY85, suggesting complete suppression of the pathogen. In vitro lesion control experiments demonstrated that 96 h after inoculation with HY85, the characteristic yellow urediniospore masses on the lesions were entirely replaced by the white mycelium of the hyperparasitic fungus. The control efficacy of strain HY85 against coffee rust fungus was 66.67%. Scanning electron microscopy revealed that strain HY85 caused significant morphological alterations in the urediniospores, including indentation and collapse, leading to severe structural damage. These findings underscore the capability of A. persicinum to disrupt the life cycle of H. vastatrix and its potential as an effective biocontrol agent strain for CLR management.