Screening Barley Doubled Haploid Lines for Spot Blotch Resistance and Its Interrelationship with Common Root Rot Resistance

Spot blotch (SB) caused by the fungus Cochliobolus sativus, is a devastating disease of barley that causes significant yield losses worldwide. Development of resistant cultivars is generally considered difficult, therefore, in this work; doubled haploid (DH) lines derived from crossing common cultivars currently used in Europe and West Asia were tested for reaction to C. sativus. Following field experiments 40 lines were evaluated under artificial infection conditions during two consecutive seasons. Results demonstrated significant differences among barley lines with a broad spectrum of disease responses ranging from highly susceptible to highly resistant, which were consistent in both seasons. However, seven promising lines had slightly lower SB disease than the others. On the other hand, positive correlation (r=0.80, P=0.01) between SB and common root rot (CRR; caused also by C. sativus) was found when these highly resistant DH lines were inoculated by the same virulent pathotype Pt4, which could suggest that resistance to C. sativus in the sub-crown internodes and leaves might involve similar defence mechanisms. The newly identified DH resistance lines can be potential donors for ongoing SB and CRR resistance breeding program to generate high-yielding commercial barley cultivars.