Endophytic Pseudomonas pergaminensis DR1 controls anthracnose and promotes growth of medicinal orchid Pleione bulbocodioides

Abstract

Pleione species are valued ornamental plants and the source of the traditional Chinese medicine “Bingqiuzi.” In this study, pathogenic fungi were isolated from diseased leaves and pseudobulbs of Pleione bulbocodioides (Franch.) Rolfe in Yunnan Province, China. Through Koch’s postulates, two pathogenic strains were obtained and identified as Colletotrichum orchidophilum based on morphological characterization and multilocus phylogenetic analyses ( ITS , CHS , TUB2 , GAPDH , and ACT ). Notably, the two strains exhibited significant differences in sporulation capacity and conidial length. An antagonistic bacterial strain, DR1, was isolated from the roots of wild P. bulbocodioides and identified as Pseudomonas pergaminensis based on phylogenetic analysis of 16S rRNA and housekeeping genes ( gyrB , rpoB , and rpoD ). Strain DR1 exhibited strong antagonistic activity against C. orchidophilum in dual culture assays, with an inhibition rate of up to 71.28%, and demonstrated the ability to produce siderophores and proteases. The volatile organic compounds (VOCs) produced by DR1 achieved inhibition rates of 53.04% and 48.08% against the two pathogenic strains, respectively. In greenhouse trials, 4 months after application of the DR1 suspension, the disease index was significantly reduced, with a control efficacy of 62.5% (beta regression model), and the number of newly emerged leaves increased by 198% compared with the control ( P < 0.01). Based on the genomic information of the P. pergaminensis type strain, the potential mechanisms by which DR1 may promote plant growth and suppress the pathogen were preliminarily discussed. This study conducted a preliminary identification of C. orchidophilum causing anthracnose on P. bulbocodioides and demonstrated that P. pergaminensis DR1 has promising biocontrol and growth-promoting potential, providing a valuable microbial resource for the sustainable cultivation of medicinal orchids.