The relationship between seedling infection types and field reactions to leaf scald in Clipper barley backcross lines

Abstract

Eighty-four third backcross (BC) lines of barley with different chromosomal segments of Hordeum spontaneum in a H. vulgare (cv. Clipper) background, were tested for resistance to a mixture of isolates of Rhynchosporium secalis using a seedling assay. Twelve of the lines were classed as resistant, including two which segregated for resistance. Plants tested using the seedling assay were subsequently planted in the field in Canberra and levels of disease monitored through to plant maturity. Seedling assay scores and field disease levels were closely correlated (r = 0.72, P < 0.001). Furthermore, grain yields for resistant BC-lines were 25% higher, on average, than those for susceptible lines. A separate field trial containing a selection of these lines was conducted in a scald-prone barley growing area (Wagga Wagga). The results obtained were consistent with those from the Canberra trial. The experiments demonstrate that resistances to leaf scald in H. spontaneum, first detected as seedling response types, also function to increase the resistance of barley throughout the growing season.