Virulence analysis of novel Beauveria bassiana strains isolated from three different climatic zones against Locusta migratoria.

Biological control using entomopathogenic fungi is a promising alternative to the chemical control of locusts. The current study collected many trains of Beauveria bassiana and tested their suitablility for migratory locust management. Twenty fungal stains were isolated from the soil (collected from three different climatic zones in China) using the Galleria mellonella bait protocol. The phylogenetic analysis of the collected fungal strains based on ITS1 and ITS4 sequences revealed that they all belonged to B. bassiana. The results of pathogenicity testing against the third nymphal instar of Locusta migratoria showed that eight strains were highly pathogenic, causing 100% mortality within 10 days of treatment. The LC₅₀ values of the strains B. bassiana BJ (BbBJ), B. bassiana ZJ1(BbZJ1), and B. bassiana HN1 (BbHN1) were 2.27 × 10⁵, 0.16 × 10⁵ and 1.02 × 10⁵ conidia^/mL, respectively indicating the lowest LC₅₀ values for strains collected from Beijing, Zhejiang, and Hainan, respectively. The LT₅₀ values for fourth and fifth instar larvae and the horizontal transmission ability of strain BbZJ1 were 4.62 days, 8.69 days and 91.7% respectively proving to be the best among the three selected strains. In addition, analysis of virulence factors of the three regionally best strains showed that BbZJ1 had the highest germination rate, fastest growth (by 7.06 mm day⁻¹), produced the most conidia (16.03 × 10⁶ conidia mm⁻²), had higher protease activity, and a hydrophobicity value of 97.31%. BbZJ1 strain has an excellent pathogenicity against local migratory locust, and has the potential for developing fungal biopesticide for controlling local locusts. [ABSTRACT FROM AUTHOR]