Water Deficit During the Vegetative Stage Alters the Structure of Root-Associated Microbial Communities in Local North Sulawesi Rice

Song Nio and Daniel Mantilen Ludong

Background and Objective: Changes in rhizosphere microbial populations have been reported in response to drought, temperature fluctuations, CO₂ levels and other environmental factors. However, the structure of the root-associated microbes in local North Sulawesi rice using a metagenomic approach has not yet been investigated. This study examined the microbial community structure in local North Sulawesi rice (cv. Superwin) under drought (water deficit) conditions compared to well-watered conditions at the vegetative phase. Materials and Methods: Rice plants were grown in polybags filled with a 5:1:1 mixture of garden soil, compost and rice husks and were allowed to grow until the four-fully-expanded leaf stage. They were then subjected to two treatments for 14 days: well-watered conditions (irrigated to 100% field capacity) and water deficit conditions (0% field capacity). Root samples were collected for next-generation sequencing analysis to assess molecular response of Superwin rice to water deficit. Results: During drought, several root-associated microbes were more prevalent, including Nitrospirota at the phylum level, Rubrobacteria at the class level, Micrococcales at the order level, Gaiellaceae at the family level, Gaiella at the genus level and Gaiella occulta at the species level. Conclusion: Root-associated microbes, including taxa Nitrospirota, Rubrobacteria, Micrococcales, Gaiellaceae, Gaiella and Gaiella occulta, have a higher relative abundance in rice plants under water deficit. Gaiella occulta serves as sensitive indicator of water deficit in North Sulawesi local rice, i.e. Superwin.

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