Resistance of New Zealand barley cultivars to scald, caused by Rhynchosporium secalis

Abstract

The resistance of New Zealand barley cultivars to leaf scald, caused by Rhynchosporium secalis, was assessed under conditions of high disease pressure in two autumn-sown disease nurseries. Assessments of disease severity were made at several growth stages and area under the disease progress curves calculated. Cultivars ranged from highly resistant to highly susceptible, with several cultivars showing intermediate levels of resistance. Relative disease levels between cultivars were largely consistent between assessment dates. Subsets of these cultivars were spring-sown in three trials situated within commercial crops, where disease pressures ranged from low to high. Two trials, one in Canterbury and one in the Wanganui district, consisted of four cultivars, with or without fungicide treatments. The other trial, in Southland, consisted of eight cultivars. Scald severity differed between cultivars. Partial resistance to scald, such as that found in Regatta, is likely to be more affected by environment than high level resistance. Such cultivars will probably require fungicide control of scald when inoculum pressure is high.