First report of Fusarium pseudograminearum causing root and crown rot in the halophyte Salicornia europaea

Salicornia europaea L. (glasswort), a euhalophyte in the Amaranthaceae family, is a valuable green vegetable. In July 2021, an outbreak of root and crown rot disease occurred on S. europaea grown in peat-filled pots under greenhouse. Symptoms appeared on 20–25% of 6-month-old plants. The fungus was identifed as F. pseudograminearum by means of morphological observations and molecular sequence analysis based on tef-1α gene (EF-1/EF-2) and using species-specifc PCR primers (Fp1-1/Fp1-2). This pathogen is known as the causal agent of crown rot in cereals and has sporadically been reported on wheat plants and seeds of soybean and vetch in Europe. A pathogenicity test was then conducted in a growth chamber to fulfll Koch’s postulates. Forty-eight seedlings (57 days after sowing) were grown in aerated non-saline nutrient solution in which a suspension of F. pseudograminearum macroconidia had been poured (fnal concentration 105 ml−1). Other 48 plants (controls) were grown hydroponically in a separate growth chamber and inoculated with sterile distilled water. Twenty-four days after inoculation (dpi), half of control and inoculated plants was transferred into a new sterile nutrient solution while the other half was transplanted into pots flled with sterilized peat. After 80 dpi, 100% of pot-grown plants showed root and crown rot symptoms whereas only 70% of infected hydroponically-grown plants developed symptoms. No evidence of disease was observed in the controls. F. pseudograminearum was consistently re-isolated from diseased plants in both cultivation systems (64.5–83.0%). Further investigations are in progress on this new pathosystem in saltwater hydroponics.