Characterization of Differences of Seed Endophytic Microbiome in Conventional and Organic Rice by Amplicon-based Sequencing and Culturing Methods

ABSTRACT The seed serves as the primary source of microbial inoculum for plant microbiota, playing a crucial role in establishing microbial populations in plants across subsequent generations, ultimately impacting plant growth and its overall health. Cropping conditions, especially farming practices, can influence the composition and functionality of the seed microbiome. Very little is known about the differences in seed microbiome between organic and conventional production systems. In this study, we characterized the endophytic microbial populations in seeds of rice grown under organic and conventional management practices through culture-dependent and independent analyses. The V4 region of 16S rRNA was used for bacterial taxa identification, and the ITS1 region was used in the identification of fungal taxa. Our results revealed significantly higher Shannon and Simpson indices for bacterial diversity in the conventional farming system whereas the fungal diversity was higher for observed, Shannon, and Simpson indices in the organic farming system. The cultivable endophytic bacteria were isolated and identified by the full-length 16S rRNA gene. There was no difference in culturable endophytic bacterial isolates in rice seeds grown under both conventional and organic farming systems. Among 33 unique isolates tested in vitro , three bacteria Bacillus sp. ST24, Burkholderia sp. OR5, and Pantoea sp. ST25, showed antagonistic activities against Marasmius graminum, Rhizoctonia solani AG4, and R. solani AG11, the fungal pathogens causing rice seedling blight. IMPORTANCE In this paper, we studied the differences in the endophytic microbial composition of rice seeds grown in conventional and organic farming systems. Our results demonstrate a greater bacterial diversity in conventional farming, while organic farming showcases a higher fungal diversity. Additionally, our research reveals the ability of seed bacterial endophytes to inhibit the growth of three fungal pathogens responsible for causing seedling blight in rice. This study provides valuable insights into the potential use of beneficial seed microbial endophytes for developing a novel microbiome-based strategy in the management rice diseases. Such an approach has the potential to enhance overall plant health and improve crop productivity.