Evaluation of Entomopathogenic Fungi Isolates for Control of Sweetpotato Weevils (Cylas formicarius Fab.)
Vang Thi Tuyet Loan1, Tran Van Hai2, Trinh Thi Xuan2
1An Giang University, Crop Science Department, Vietnam
The objective of this work is to identify five entomopathogenic fungi isolates collected from Hungary using molecular techniques and evaluate their virulence to sweetpotato weevils (Cylas formicarius Fab.) in laboratory conditions. Molecular identification was made by sequencing the ITS - rDNA region. Pathogenicity study was based on mortality of adults of Cylas formicarius inoculated with Conidia dasoge 108 conidia/ml. The results of sequencing of the ITS - rDNA region indicates that the MHU1, MHU2 and MHU3 isolates belong to the clade of Metarhizium anisopliae, which was identified as Metarhizum anisopliae with the sequences of ITS – rDNA region similar from 99% to 100%. Other two isolates MHU4 and MHU5 showed a high degree of siminarity with Pencillium variabile (99%). Laboratory bioassays were conducted to assess the pathogenicity of 4 isolates of Metarhizium anisopliae (MHU1, MHU2, MHU3 and MVN1) and 2 isolates of Penicillium variabile (MHU4 and MHU5) toward sweetpotato weevils (Cylas formicarius Fab.). The Metarhizium anisopliae-MVN1 that was isolated from sweetpotato weevils death in Vietnam used as control. The pathogenicity tests show that three Metarhizium anisopliae isolates (MHU1¬, MHU3 and MVN1) caused early adult sweetpotato weevils adults mortality rate from 44.4% to 50% at four days after treatment. At six days after treatment, two Metarhizium anisopliae (MHU1¬ and MHU3) isolates were highly virulence on adult sweetpotato weevils adults with the mortalities 92.5% and 94.2%, repectively, and same the virulence degree of Metarhizium anisopliae-MVN1 isolate (100% mortality rate). Four isolates Metarhizium anisopliae (MHU1, MHU2, MHU3 and MVN1) reached 100% mortality rate as the same the rate of colony growth on death adult sweetpotato weevils adults at 10 days after treatment. However, two isolates of Penicillium variabiles were not pathogenic to Cylas formicarius with from 2.2% to 3.3% mortality rate. It is proved that two Metarhizium anisopliae isolates (MHU1 and MHU3) have great potential as biological control agents against sweetpotato weevils.
Keywords: ITS - rDNA molecular, Metarhizium anisopliae, sweetpotato weevil
Contact Address: Vang Thi Tuyet Loan, An Giang University, Crop Science Department, 18 Ung Van Khiem Street Dong Xuyen Wrad, 90116 Long Xuyen, Vietnam, e-mail: vttloanagu.edu.vn