Pyrenophora teres growth and severity of net blotch on barley under salt stress

Pyrenophora teres causes one of the most destructive barley diseases in semi-arid production areas worldwide. With the burgeoning issue of soil salinization, this study focused on the effect of salt in combination with temperature and light on growth of P. teres and the response of barley to the pathogen. The growth of four isolates of P. teres (Pt12, Pt14, Pt16 and Pt18) was dependent on the media (potato dextrose agar (PDA), oatmeal agar or carrot meal agar). The growth of the P. teres isolates decreased with increasing NaCl concentration from 50 to 700 mM (except Pt14 at 50 mM) in comparison to 0 mM on PDA. At 0 to 150 mM NaCl P. teres isolate Pt18 showed more growth at 25 °C compared to at 15 °C or 35 °C, but at concentrations >200 mM of NaCl concentration, the salt reduced growth more than the temperature. A 16 h photoperiod induced better growth of P. teres isolate Pt18 at 0 to 200 mM of NaCl in comparison to constant darkness; at concentrations >200 mM fungal growth was influenced mostly by NaCl concentration. The growth of P. teres isolate Pt18 was more sensitive to NaCl in comparison to polyethylene glycol 6000 when both compounds were applied at iso-osmotic concentration greater than 248 mOsm kg−1. After 6 days of culture at 50–700 mM NaCl, isolate Pt18 showed reduced growth compared to at 0 mM NaCl when transferred to salt-free PDA. Severity of net blotch on detached leaves of barley inoculated with isolates Pt14, Pt16 and Pt18 decreased when plant had been irrigated with 50 mM NaCl, whereas infection increased when irrigated with water at concentrations >200 mM NaCl. The results indicate that the irrigation of barley plants with moderately salt-laden water can improve barley resistance to P. teres, but greater concentrations of salinity may increase infection of barley by P. teres.