Abstract
Mycorrhizal helper bacteria (MHB) play a crucial role in promoting mycorrhizal associations between roots and fungi. Previous studies have identified Burkholderiales bacteria, specifically Paraburkholderia fungorum GIB024, Caballeronia sordidicola GIB028, and Janthinobacterium agaricidamnosum GIB029 as potential MHB of Rhizopogon roseolus TUFC 10010. This study investigated the role of these bacterial strains in interactions with the Japanese black pine (Pinus thunbergii). Seedlings of P. thunbergii were inoculated with R. roseolus and bacteria in a co-culture agar system for 12 weeks. The results indicated that all three bacterial strains enhanced mycorrhizal formation compared with the control (no bacterial treatment). Treatment with J. agaricidamnosum GIB029 resulted in the greatest mycorrhizal formation, followed by C. sordidicola GIB028 and P. fungorum GIB024. Additionally, these bacteria increased total plant biomass. When combined with R. roseolus, the addition of bacterial strains J. agaricidamnosum GIB029 and C. sordidicola GIB028 effectively reduced the number of yellowing leaves in Pinus thunbergii. These findings suggested that these bacteria function as MHB by promoting mycorrhizal formation and plant growth. Furthermore, they may play a role in improving plant vigor by reducing the number of yellow leaves.
