Effect of Growth Stage on Resistance to Drechslera teres f. teres in Barley

Three experiments were conducted to evaluate seedling and adult plant resistance to Drechslera teres f. teres in barley lines with a potential use as resistance sources in barley breeding. Disease resistance of barley seedhngs, inoculated in the glasshouse and growth chatnber at the one- and two-leaf stages, was significantly (P 0.05) correlated with disease reactions on the fourth and flag leaves of barley plants grown in growth chambers (r = 0.84- 0.94) as well as with disease levels recorded on the three uppermost leaves in a field experiment (r — 0.64). Several of the barley lines showed no correlation, demonstrating either improved or decreased disease resistance at later growth stages. Six barley lines (Alexis, Heartland, Kinnan, CI4922, CI9776 and SWl 114-93) had the same ranking in disease resistance to D. teres when damaged (punctured) leaves were inoculated with a drop of spore suspension as when undamaged leaves were spray-inoculated with a spore suspension.