B. Pezzarossa¹, E. Borghesi¹, R. Pini¹, F. Bretzel¹, R. Maggini² and F. Malorgio^2
1 Research Institute on Terrestrial Ecosystems (IRET), CNR, Pisa, Italy
² Department of Agriculture, Food and Environment, University of Pisa, Pisa, Italy

SUMMARY The rhizomes of Iris pallida, known as orris root, are an important source of essential oils for the perfume industry and of the powder used for making gins and cordials. Rhizomes contain irones, ketone compounds formed from iridals during post-harvest ageing. Iris pallida is cultivated in Europe, mainly in Italy and France, and in Morocco and India. The Italian product is highly sought after due to its qualitative characteristics. Little is known about the influence of pedo-climatic conditions on the quality of the cultivated rhizomes. Our investigation was carried out in the Iris pallida cultivation area of Tuscany (Italy) and intended to assess the possible relationship between the chemical profile of iridals, the climate, and soil properties. Seven farms were selected based on the significance of the cultivated surface, i.e., minimum area of 0.3 ha, and the proximity to the weather stations. A climate survey was conducted. Soil was analysed for the main physico-chemical characteristics and rhizomes for the content of iridals. Our results showed that despite the different physico-chemical soil properties and different rainfall regimes that characterize the cultivation areas, the iridals concentrations in rhizomes did not differ among farms. This supports the hypothesis that Iris pallida behaves like a hardy species by adapting well to different cultivation environments, especially to both non-calcareous and calcareous soils. The observed adaptability of this species to different environments might contribute to the spread of this crop even in marginal soils. This could generate more income for farmers. The cultivation of terrace soil could improve soil and water conservation, as well as decrease soil erosion. Further studies are needed to understand the dynamics of the accumulation of iridals in the rhizomes, and to identify the factors that influence the iridal transformation in irones. Keywords iridals, iripallidal, irones, orris root, soil characteristics, Tuscany (Italy)

Significance of this study What is already known on this subject? The ketone compounds (irones) contained in rhizomes of Iris pallida and formed by the chemical oxidative degradation of iridals, which are initially present in the rhizomes, seem to be affected by several factors such as the potassium fertilization, the age of the plant, the post-harvest conditions of the rhizomes, and the different extraction techniques. Little is known about the influence of pedo-climatic conditions and cultural practices on the quality of the cultivated rhizomes. What are the new findings? Despite the different physico-chemical soil properties and different rainfall regimes that characterize the cultivation areas under study, no significant differences in the iridals concentrations were observed. Soil and climate conditions might not have markedly influenced the accumulation of iridals, and support the hypothesis that Iris pallida behaves like a hardy species by adapting well to different environments, especially to both non-calcareous and calcareous soils. What is the expected impact on horticulture? The observed adaptability of Iris pallida to the different pedo-climatic conditions might contribute to the spread of this crop even in marginal soils. This could generate more income for farmers, who would otherwise not be able to cultivate less fertile soils. The cultivation of terraced soil could further improve soil and water conservation, as well as decrease soil erosion.

E-mail: beatrice.pezzarossa@cnr.it  

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Received: 14 December 2018 | Accepted: 20 May 2019 | Published: 4 May 2020 | Available online: 4 May 2020