Effects of co-inoculation of Delftia acidovorans RAY209 on the growth of Bradyrhizobium diazoefficiens USDA110 inoculated Glycine max

Today's global prosperity and food abundance has largely been brought about by the extensive use of chemical fertilizers, and it is predicted that even more pressure on agrifood systems will occur in the coming decades. The cumulative impacts of this increased pressure will be driven by continued population growth, an unprecedented and growing demand for high quality protein, environmental degradation caused by chemical fertilizers, and also be the need for agriculture to be more sustainable. Inoculating crops with plant growth-promoting rhizobacteria (PGPR) has emerged to fill in the gap between the growing demand for food and sustainable agriculture as it promotes plant growth, reduces crop susceptibility to abiotic and biotic stress, and ultimately facilitates producing foods in a sustainable manner. Besides the well-established and widely-applied legume-rhizobia interaction, the co-inoculation of soybean with Bradyrhizobium and other plant PGPR has gain increasing popularity attributed to the observed synergistic effects that result in improved plant growth promotion and stress tolerance. The objective of the current investigation was to examine whether co-inoculating soybean (Glycine max L. (Merr.) with Bradyrhizobium diazoeffeciens USDA110 and PGPR Delftia acidovorans RAY209 can enhance plant growth and enhance stress tolerance, as well as to identify the underlying mechanisms. The first study successfully cultured and tested the salt tolerance of USDA110 and RAY209 in vitro where RAY209 exhibit good tolerance in salt relative to USDA110. The effect of different inoculation methods on plant growth and stress tolerance was then examined in a gnotobiotic system. Confocal laser scanning microscopy confirmed the host specificity between inoculant strains and soybean. Although no significant differences were found in growth parameters between soybean roots inoculated with USDA110 and RAY209+USDA110, RAY209 produced considerable amounts of indole-3-acetic acid (IAA), a phytohormone that can potentially stimulate plant growth and cause modification of root architecture. Differential transcriptome analysis of 30-day inoculated seedlings revealed that stress conditions had a larger effect on gene expression in soybean roots than inoculation method. However, co-inoculation with RAY209 and USDA110 did reveal the increased expression of genes associated with xyloglucan catabolism and subsequent cell wall expansion, which could initiate plant cell growth and active proline metabolism under salt stress conditions. These findings suggest that RAY209 may play a crucial role in plant growth-promotion (PGP), particularly in soybean-Bradyrhizobia symbiosis. Further studies are necessary to fully unravel the extent of IAA production by RAY209 in vivo and its effect on plant growth and the biological processes related to root morphology.

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Applied Microbiology

Grantor

University of Saskatchewan

Year dc:date.issued

2023

Author dc:creator

• Wu, Xuxiaochen

Advisors dc:contributor.advisor

• Korber, Darren
• Bergsveinson, Jordyn

Committee members dc:contributor.committeemember

• Eskiw, Chris
• Nickerson, Michael
• White, Aaron

• Plant growth promoting rhizobacteria
• sustainable agriculture

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/15150

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/15150