Endophytic Beauveria bassiana promoted growth in Phaseolus vulgaris L. with causing negative effects on Frankliniella occidentalis by reducing its feeding and fitness

Inoculating plants with entomopathogenic fungi can improve plant resistance to pests and promote growth, suggesting that this approach is a sustainable method for controlling insect pests. Two Beauveria bassiana isolates (GZGY-1-3 and XJWLMQ-32) were inoculated via three different methods (foliar, soil and seed treatments) to assess the endophytic colonization and plant growth of bean (Phaseolus vulgaris) plants at 7, 14 and 21 days post-inoculation (DPI). Western flower thrips (WFT), Frankliniella occidentalis Pergande, feeding on B. bassiana-inoculated bean leaves was carried out by foliar spraying. A two-sex life table study was generated to determine the effect of feeding on B. bassiana-inoculated bean plants on the development and fecundity of WFT. Results showed that both isolates endophytically colonized leaves, stems and roots via the three inoculation methods, and the colonization rates from bean plants varied with the inoculation methods and decreased as the DPI increased. Root weight, plant weight and leaf numbers of bean were promoted after both B. bassiana isolates inoculation. Plant growth was strongly promoted by the XJWLMQ-32 isolate. The inoculated plants could deter feeding by WFT, and the life table study results showed that feeding on the inoculated plants resulted in a slow development rate (r = 0.15 d^-1, λ = 1.16 d^-1) and low fecundity (F = 27.62 eggs per female) in WFT. This study highlights that B. bassiana can endophytically colonize P. vulgaris and promote plant growth and that this plant–microbe symbiosis can deter WFT feeding and inhibit population growth.