Abstract:

A new pathogenic strain of Pu. XHz from Citrus sinensis fruit showing symptoms like blue-green mold was identified. Pu. XHz formed white round colonies on PDA medium. Large numbers of blue-gray spores and exudative droplets appeared in the late stage. On CA medium，it showed fireworks-shaped radial colonies. Meanwhile，the colonies of Pu. XHz formed on CYA medium looked like concentric circles. When cultured on G25N medium，white mycelium colonies developed well but did not produce conidia. The size of oval-shaped Pu. XHz conidia was ranging from 4.48–8.37 μm to 2.65–5.24 μm. Pathogenicity test showed，water-soaked ring spots formed 3 days post inoculation（dpi）on Fortunella margarit，Murcott and Citrus sinensis Osbeck‘Newhall’. In about 10 dpi，large quantities of blue-gray conidia and conidiophore with typical character of whisker molds formed in the site of infected lesions. Further analysis by ITS sequencing verified Pu. XHz was a new strain of P. ulaiense. It showed 99% homology with that of P. ulaiense stain SU-9 deposited in GenBank. Our present study verified that Pu. XHz was the causal agent of citrus whisker mold，which laid a basic foundation for further study on the pathogenicity of P. ulaiense.

Key words: citrus, fruit rot, pathogen identification, Penicillium ulaiense