Identification and Characterization of the Core Rice Seed Microbiome

The use of microbes in agriculture for enhancing crop production is an emerging alternative to chemical fertilizers and pesticides; however, their effectiveness is often limited by factors such as host genotype and variability in geographic location. To address this issue, the microbiomes of six different rice (Oryza sativa) seeds, sourced from two locations in Arkansas, U.S.A. of two different genotypes and two harvest years, were characterized. The bacterial and fungal communities were identified in each of four seed compartments (grain, outer grain, husk, and outer husk) using high throughput Illumine MiSeq sequencing. More unique amplicon sequence variants were identified in the outer seed husk and least in the grain compartment for both the fungal and bacterial microbiomes, however this only resulted in a decrease in diversity for the fungal communities. Principal component analysis indicated that each tissue compartment harbored relatively distinct bacterial and fungal communities for the three innermost compartments. A bacterial and fungal core microbiome shared among the six seed types for each compartment was identified. Key bacterial genera in the core across all compartments were Sphingomonas, Methylobacterium, and taxa in the family Enterobacteriaceae, members of which have been reported to support rice growth. Compared with the bacterial core, more fungal taxa were identified, possibly resulting from the more abundant reads after filtering, and key genera identified were Alternaria, Hannaella, and members of the order Pleosporales. These core members represent valuable candidates for manipulating the rice microbiome, decreasing the use of chemicals while increasing plant performance.