Effect of Mycorrhizal Inoculation and Irrigation on Biological Properties of Sweet Pepper Rhizosphere in Organic Field Cultivation

Agnieszka Jamiołkowska,Halina Buczkowska,Jarosław Grządziel,Marek Kopacki,Barbara Skwaryło-Bednarz,Elżbieta Patkowska,Anna Gałązka

doi:10.3390/agronomy10111693

Abstract

The aim of the study was to evaluate the influence of mycorrhizal fungi (MF) and irrigation on biological properties of sweet pepper rhizosphere in organic field cultivation. For this purpose, MF were applied to plants in the form of commercial mycorrhizal inoculum (Rhizophagus aggregatus, R. intraradices, Claroideoglomus etunicatum, Endogone mosseae, Funneliformis caledonium, and Gigaspora margarita) and irrigation according to the combinations: mycorrhized plants (PM), mycorrhized and irrigated plants (PMI), and irrigated plants (PI). Plants without MF and irrigation served as the absolute control (P). The study used classic and molecular techniques, assessing catalase activity, biodiversity of soil microorganisms (soil DNA analysis), and the Community-Level Physiological Profiles (CLPP) analysis using Biolog EcoPlates. The highest catalase activity was recorded in the control and mycorrhized soil sample. The highest total number of bacteria was noted in the rhizosphere of control plants (P) and irrigated plants, while the lowest number in the rhizosphere of mycorrhized and irrigated plants. Plant irrigation contributed to the increase in the total number of fungi in the rhizosphere. The rhizospheric soil of PM and PMI were characterized by the highest utilization of amines, amides, and amino acids, whereas the lowest level of utilization was detected in the P and PI rhizospheres. The highest biodiversity and metabolic activity were observed in the rhizospheres from the PMI and PM samples, whereas lower catabolic activity were recorded in the P and PI rhizospheres. The mycorrhization of crops improved the biological properties of the rhizosphere, especially under conditions of drought stress.

Highlights

The rhizosphere is a zone of intense microbial activity and shows a close relationship between plant, soil, and microorganisms
The analysis showed that catalase activity in the soil under the cultivation of peppers in the organic production was determined to a varying degree by the studied factors: years of research, mycorrhizal inoculation and irrigation, soil sampling zones, and plant developmental stages (Table 1)
The lowest similarity was recorded between the rhizosphere of the control plants (P) and the other studied communities (Figure 1). These results indicate that the irrigation of plants during the growing season limited the development of fungal colonies, and the application of mycorrhizal fungi (MF) contributed to the increase in their numbers and biodiversity

Summary

Introduction

The rhizosphere is a zone of intense microbial activity and shows a close relationship between plant, soil, and microorganisms. It is characterized by biological activity, which, in turn, is one of the factors determining the growth of plants and their resistance to pathogens [1,2]. The activity of dehydrogenases, phosphatases, and catalases are most often assessed in the soil [8,9]. It seems interesting to determine the activity of catalase, as it is an intracellular enzyme involved in the metabolism of microorganisms that reduces the effects of oxidative stress [10,11,12]. The activity of catalase in soil depends, inter alia, on the content of organic matter, heavy metals, mineral and organic fertilization, and soil depth but, on the activity of dehydrogenases [9,13]

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