Different Responses to Salinity of Pythium spp. Causing Root Rot on Atriplex hortensis var. rubra Grown in Hydroponics

Emiliano Delli Compagni (), Bruno Bighignoli, Piera Quattrocelli, Irene Nicolini, Marco Battellino, Alberto Pardossi and Susanna Pecchia ()
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Emiliano Delli Compagni: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Bruno Bighignoli: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Piera Quattrocelli: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Irene Nicolini: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Marco Battellino: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Alberto Pardossi: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy
Susanna Pecchia: Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy

Agriculture, 2025, vol. 15, issue 15, 1-24

Abstract: Atriplex hortensis var. rubra (red orache, RO) is a halotolerant species rich in nutraceutical compounds, which makes it a valuable crop for human nutrition. This plant could also be exploited for phytoremediation of contaminated soil and wastewater, and for saline aquaponics. A root rot disease was observed on hydroponically grown RO plants, caused by Pythium deliense and Pythium Cluster B2a sp. Identification was based on morphology, molecular analysis (ITS and COI), and phylogenetic analysis. We assessed disease severity in plants grown in a growth chamber with nutrient solutions containing different NaCl concentrations (0, 7, and 14 g L −1 NaCl). In vitro growth at different salinity levels and temperatures was also evaluated. Both Pythium species were pathogenic but showed different responses. Pythium deliense was significantly more virulent than Pythium Cluster B2a sp., causing a steady reduction in root dry weight (RDW) of 70% across all salinity levels. Pythium Cluster B2a sp. reduced RDW by 50% at 0 and 7 g L −1 NaCl while no symptoms were observed at 14 g L −1 NaCl. Pythium deliense grew best at 7 and 14 g L −1 NaCl, while Pythium Cluster B2a sp. growth was reduced at 14 g L −1 NaCl. Both pathogens had an optimum temperature of 30 °C. This is the first report of Pythium spp. causing root rot on RO grown hydroponically. The effective use of halophytic crops must consider pathogen occurrence and fitness in saline conditions.

Keywords: halophytes; hydroponics; Oomycota; Pythium deliense; Pythium Cluster B2a sp.; plant pathology; salinity (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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