Isolation and characterization of Aschersonia placenta from citrus orchards and its pathogenicity towards Dialeurodes citri (Ashmead)

For selecting potential biological agents to control Dialeurodes citri, a major insect pest in China's citrus orchards, 75 native Aschersonia isolates were selected from infected whiteflies in citrus orchards and were evaluated for virulence to third instar nymphs of D. citri at a concentration of 1 × 106 conidia/ml. The mortality rates of D. citri varied from 0% to 72.70%. Among the 75 Aschersonia isolates, three (HB10, HB12 and ZJ9) were the most virulent and pathogenic to D. citri and caused more than 69% mortality. The 50% lethal concentration (LC50) values of them were 1.86 × 106, 3.40 × 106 and 6.81 × 106 conidia/ml, respectively. The three isolates also produced conidia abundantly on potato dextrose agar medium (3.95 × 106, 6.19 × 106 and 7.34 × 106 conidia/cm2, respectively). They were identified to be Aschersonia placenta based on their morphological analysis. Phylogenetic analysis showed that these three highly virulent Aschersonia isolates belong to a strongly supported clade that includes two other A. placenta isolates obtained from Vietnam and Thailand. In summary, these results indicate the possibility of developing the three most virulent A. placenta isolates as microbiological control agents against citrus whitefly.

Highlights► The mortality of Dialeurodes citri varied from 0% to 72.70%. ► Three most virulent isolates were identified to be Aschersonia placenta. ► PRB1 based clade were correlated with morphological characters. ► Three virulent isolates belong to a clade including other two A. placenta isolates.