Impact of Faba Bean-Seed Rhizobial Inoculation on Microbial Activity in the Rhizosphere Soil during Growing Season.

Anna Siczek,Jerzy Lipiec

doi:10.3390/ijms17050784

Abstract

Inoculation of legume seeds with Rhizobium affects soil microbial community and processes, especially in the rhizosphere. This study aimed at assessing the effect of Rhizobium inoculation on microbial activity in the faba bean rhizosphere during the growing season in a field experiment on a Haplic Luvisol derived from loess. Faba bean (Vicia faba L.) seeds were non-inoculated (NI) or inoculated (I) with Rhizobium leguminosarum bv. viciae and sown. The rhizosphere soil was analyzed for the enzymatic activities of dehydrogenases, urease, protease and acid phosphomonoesterase, and functional diversity (catabolic potential) using the Average Well Color Development, Shannon-Weaver, and Richness indices following the community level physiological profiling from Biolog EcoPlate™. The analyses were done on three occasions corresponding to the growth stages of: 5–6 leaf, flowering, and pod formation. The enzymatic activities were higher in I than NI (p < 0.05) throughout the growing season. However, none of the functional diversity indices differed significantly under both treatments, regardless of the growth stage. This work showed that the functional diversity of the microbial communities was a less sensitive tool than enzyme activities in assessment of rhizobial inoculation effects on rhizosphere microbial activity.

Highlights

Gram-negative soil bacteria of the genus Rhizobium play a very important role in agriculture
Rhizobial inoculation resulted in increased shoot growth, number of pods, and grain yield of faba bean [2] and lentil [5], compared with non-inoculated controls
When annual averages were taken into consideration, all the evaluated enzymatic activities were improved by the inoculation of the seeds with rhizobia

Summary

Introduction

Gram-negative soil bacteria of the genus Rhizobium play a very important role in agriculture. They form a symbiotic relationship with leguminous crops resulting in biological nitrogen fixation and thereby reduction of the requirements for added nitrogenous fertilizer during the growing season. Inoculation with a R. gallicum strain induced growth of bacterial communities that had been often reported as PGPM (plant growth-promoting microorganisms) [3]. The extent of these changes was seen in the rotation crop. Rhizobial inoculation resulted in increased shoot growth, number of pods, and grain yield of faba bean [2] and lentil [5], compared with non-inoculated controls

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