• artificial inoculations.
• halophytes
• Pythium
• soil-borne pathogens
• Oomycetes

Atriplex hortensis is a halophyte species and represents an interesting new crop that can be widely used to overcome the salinization problem. The aim of this work was to study a novel pathosystem: A. hortensis/Pythium spp. We characterized two Pythium species for morphological, physiological and molecular characteristics and we evaluated their virulence in salinity conditions by artificial inoculations in hydroponic conditions.

Molecular identification of Pythium species was performed by PCR and sequence analysis of the obtained amplicons. We evaluated the in vitro growth of Pythium species at different salinity and temperature. Artificial inoculations of the Pythium species were carried out on A. hortensis cultivated in hydroponic floating system conditions using three different salinity concentrations.

Molecular studies allowed the identification of P. deliense, and Pythium sp. belonging to clade B2a. These species showed different virulence on A. hortensis under salinity conditions. P. deliense caused a higher level of mortality with more severe symptoms and a better tolerance to high salinity concentrations. Pythium sp. (clade B2a), caused less severe symptoms and plant mortality. The in vitro growth results showed an increased resistance to combined salt stress at high temperatures for P. deliense. Pythium sp. (clade B2a) showed a lower resistance to high concentrations of NaCl and a high resistance to lower temperatures.