Author: Krima Jitendra Patel
Patel, Krima Jitendra, 2024 Investigating the effect of drought on rhizosphere microbial communities and root exudates composition of wheat (Scepter and EDPIE-56)., Flinders University, College of Medicine and Public Health
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The bacterial communities that inhabit plants' roots and surrounding areas, such as the rhizosphere, bulk soil, and root endosphere, have a close relationship with them. These bacterial communities engage in complex interactions with plants and assist them in withstanding a variety of abiotic and biotic stresses. Additionally, root exudate plays a crucial role in shaping the rhizosphere microbial diversity by releasing compounds. Due to current changes in climatic conditions, drought is a major problem for agriculture. Researchers have also discovered that drought stress significantly impacts the microbial composition and root exudates of wheat. However, the effect of drought on root exudate and microbial composition are not studied together as a system. The aim of the project was to study the root exudate composition and rhizosphere microbial diversity of two wheat varieties (Scepter and EDPIE-56) under drought conditions and how root exudate influences the microbial composition under drought conditions. In this study, we analysed the rhizosphere microbial communities and root exudates from two contrasting wheat genotypes exposed to drought stress using 16S rRNA gene amplicon sequencing and Gas chromatography-Mass Spectrometry. The reduction in plant phenotypes was observed under drought conditions, with a more significant suppression in roots than in shoots. Regardless of the cultivar type, Proteobacteria was abundant in both the control and drought-stressed samples, indicating a stable microbial community. Furthermore, in EDPIE-56, there was no significant change in the microbial community under drought conditions. In drought conditions, the relative abundance of phyla in EDPIE-56 was primarily Bacteroidota and Verrucomicrobiota, marginally above that of the control group. Drought conditions in Scepter resulted in a significant alteration in Bacteroidota, Verrucomicrobiota, and Actinobacteria, indicating a substantial change in microbial composition. For root exudates, both the cultivars showed no major difference in sugar. However, the exudation of shikimic and quinic acid was higher in the drought conditions compared to the control condition. Furthermore, only EDPIE-56 exhibits the presence of amino acids such as glycine, valine, and isoleucine, under drought stress. Additionally, GABA pre-treatment of seeds (Scepter) modulated the rhizosphere microbial diversity under drought treatment, perhaps indicating more resistance against the stress.
Our results reveal that both drought and genotype drive changes in the compositions of wheat rhizosphere bacterial communities and root exudates. Understanding this shift and the mechanisms by which microbes help mitigate the adverse effects of drought stress on wheat
can enhance productivity and the development of tools and management strategies to improve the resilience of wheat plants.
Keywords: drought, wheat, root exudates, GABA
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2024
School: College of Medicine and Public Health
Supervisor: Sunita Ramesh