Synergistic Effects of Seed Endophytic Bacterial Consortia from Lactuca serriola on Phosphorus Solubilization

Abstract

Plants have evolved in association with plant-beneficial bacterial endophytes. Some of these bacteria live inside seed, known as seed endophytes, are vertically transmitted to the next generation and contribute to early seedling development. In this study, we aimed to assess the plant growth-promoting (PGP) potential of these seed endophytes. To better simulate natural conditions, we constructed bacterial consortia to evaluate their synergistic effects. From the seed endophytes of Lactuca serriola, designated as a harmful non-indigenous plant in South Korea, we selected seven bacterial strains. These strains and their consortia were screened for four key PGP traits. Among them, two strains that played a key role in consortium function were selected and co-inoculated with different isolates in L. serriola to assess their impact under phosphorus deficiency. The Kosakonia cowanii SD1 and Pantoea dispersa SD25 consortium, and Xanthomonas spp. SD2 and Stenotrophomonas maltophilia SD8 consortium enhanced soil phosphorus availability. Notably, these two consortia displayed contrasting results in in vitro assays, suggesting that these combinations utilize different mechanisms to enhance soil phosphorus availability. These findings provide valuable insights into the role of seed endophytes in the adaptability and ecological success of non-indigenous plants, contributing to a better understanding of invasive plant management.