Elsevier

Rhizosphere

Volume 15, September 2020, 100208
Rhizosphere

Growth of chamomile (Matricaria chamomilla L.) and production of essential oil stimulated by arbuscular mycorrhizal symbiosis

https://doi.org/10.1016/j.rhisph.2020.100208Get rights and content

Highlights

  • It was found 22 species of AMF in the soil-inoculum, predominanted by Diversispora tortuosa.

  • Inoculation of AMF increased growth and production of capitula and such benefits varied with the inoculum levels.

  • The presence of AMF in the soil and soil pH altered the production of capitula and EO of chamomile.

Abstract

This study aimed to evaluate the influence of arbuscular mycorrhizal fungi on the growth and production of capitula and essential oil of chamomile plants, under different growth conditions. The symbiosis between fungi of the phylum Glomeromycota and plant roots may cause changes in secondary metabolism, including the synthesis of essential oils. Increasing biomass production associated with gains in oil content promoted by mycorrhization, makes soil biota management sustainable. Two assays were carried out in a greenhouse, in plastic pots (3 L), for 150 days after emergence of the seedlings. In the first assay, plants were inoculated with soil cultivated with organic chamomile, in three levels (0, 150 and 300 g), with pH adjusted at 6.5, for evaluating the influence of the quantity of inoculum on the growth and production of plants. In the second assay (factorial design with repetition at the central point), three levels of soil pH (6.5, 7.0, 7.5) and three levels of auxin (0; 10; 20 mg L−1) were tested to identify the influence of pH and auxin on the production of chamomile capitula and essential oil. The arbuscular mycorrhizal fungi present as spores in the soil-inoculum were composed of 22 species. In the first assay, mycorrhization favored the growth and production of capitula and such benefits tended to be higher with the increase in concentration of inoculum. In the second assay, the production of capitula and essential oil was promoted by mycorrhization, with the highest content at neutral pH (0.7 mL oil in 30 g of capitula), in synergy with the highest amount of inoculum. It was concluded that the presence of arbuscular mycorrhizal fungi in the soil is the most influential variable in the production of capitula and essential oil of chamomile, but subtle differences on soil pH influenced these parameters. The levels of auxin did not influence significantly plant growth and arbuscular mycorrhizal fungi.

Introduction

Most plants have roots colonized by arbuscular mycorrhizal fungi (AMF) and the most obvious beneficial effect of this association is the increase in plant growth by increasing the uptake of nutrients, especially those of low mobility such as phosphorus (P), zinc and copper (Smith and Read, 2008). In mycorrhizal symbiosis, interactions are regulated by permanent molecular mechanisms, from the recognition of symbionts to the functional establishment of associations (Sędzielewska-Toro and Delaux, 2016). Changes in plant metabolism and plant symbiosis with AMF, result in more vigor and resistance to adverse environmental conditions by increasing the production of structural components, defense compounds and energy reserves (Smith and Read, 2008). Under drought stress, i.e. chamomile plants have decreased essential oil (EO) content and the proportions of camazulene and bisabolo oxide B, however produced more carbohydrates, proline and bisabolo oxide A (Jeshni et al., 2017). In this environmental condition, the AMF would assume high importance for increasing nutrient absorption and protective adaptation capacity (Song, 2005).

According to the literature data, the production of biomass and metabolites in medicinal plants can be modulated not only by environmental and crop factors, but also by mycorrhization (Beltrame et al., 2019, Lermen et al., 2017, 2019; Morelli et al., 2017; Cruz et al., 2019, 2020). Singh et al. (2010) studied green tea [Camellia sinensis (L.) Kuntze, Theaceae] and after two years observed that mycorrhization significantly increased plant growth and the levels of total amino acids and proteins (up to 100% increase), total sugars (16%), reducing sugars (45%) and non-reducing sugars (69%). Regarding secondary metabolism compounds, the authors found an increase in the concentrations of total polyphenols (15%) and caffeine (34%).

Geneva et al. (2010) evaluated EO quantitative standard of Salvia officinalis L. (Lamiaceae) inoculated with Glomus intraradices and observed increases in dry matter production and in the content of antioxidant metabolites (ascorbic acid and glutathione). Zubek et al. (2010) evaluated specimens of Inula ensifolia L. (Asteraceae) inoculated with Glomus intraradices, G. clarum and AMF native community and obtained higher levels of thymol in mycorrhizal plants. In Hipericum perfuratum L. (Hipericaceae), Zubek et al. (2012) found an increase in hypericin, the main active compound of the plant after mycorrhization. Barto et al. (2011), when evaluating the allelopathic potential of Alliaria petiolata Bieb. (Brassicaceae), observed higher levels of glucosinolates and flavonoids in mycorrhizal plants.

Plant growth is influenced by mycorrhization and by various environmental factors, and as the degree of root colonization by AMF and symbiotic efficiency are also modified by several environmental factors, this study included the analysis of the influence of soil pH, an important variable in the dynamics the transport and absorption of mineral nutrients in the soil solution, especially phosphorus, the key element of the AMF association (Smith and Read, 2008), as well as auxin application that is closely related to the production of strigolactones, terpenoids involved in the communication between roots and AMF (Marzec et al., 2013).

The present study was carried out in three stages, one in the field and two in potted plants. The field phase aimed to evaluate the mycorrhizal status of the chamomile plants and the diversity of the AMF communities, which formed the basis for the AMF inoculum production. Two assays were carried out in pots: first, to investigate the influence of mycorrhization and inoculum concentration on the development and production of chamomile capitula; second, to observe the influence of environmental factors (soil pH and addition of auxin) on the effect of mycorrhization on the growth, production of capitula and essential oil of chamomile.

Section snippets

Field sampling

Ten soil samples (50 g) were collected in an organic planting area of commercial chamomile, located in the metropolitan region of Curitiba, Paraná - Brazil (Mandi Erva farm) to evaluate the AMF diversity. The AMF spores were extracted by wet sieving (Gerdemann and Nicolson, 1963) and sucrose centrifugation (Jenkins, 1964). Spores were quantified under light microscopy on permanent slides with polyvinyl alcohol-lactic acid-glycerol (PVLG) and PVLG + Melzer's reagent (Morton et al., 1993). The

AMF diversity of field-produced chamomile plants

Twenty-two species were identified, distributed into eleven genera: Acaulospora (4), Ambispora (3), Claroideoglomus (3), Dentiscutata (1), Diversispora (1), Funneliformis (3), Gigaspora (1), Glomus (3), Sclerocystis (1), Scutellospora (1), and Septoglomus (1). The species with the highest number of spores were Sclerocystis sinuosa and Diversispora tortuosa, the first found in only one sample, and the second in seven samples (Table 1). We observed a high variation in the number of spores per

Conclusions

The development and production of chamomile plants are influenced by subtle changes in soil pH and by effective mycorrhizal symbiosis. Increase in the production of capitula and in the essential oil content can be obtained from the manipulation of soil pH and in the management of the AMF community in the soil. Neutral soil pH and quantity of mycorrhizal propagules close to or above 300 spores g−1 of soil at the beginning of cultivation favor the production of capitula and essential oil of

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

Odair Alberton acknowledge a research fellowship from the CNPq (National Council for Scientific and Technological Development).

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