Reaction of spring barley to common root rot under several moisture regimes: Effect on yield components, plant stand, and disease severity

The reaction of spring barley to common root rot and its effect on yield components, plant stand, and disease severity was studied under several moisture regimes. Infection of barley from natural soil inoculum, primarily Cochliobolus sativus, was augmented with inoculum of C. sativus or Fusarium culmorum to insure uniform disease pressure during plant development. In one study during the 1986 and 1987 growing seasons, a line-source sprinkler irrigation system was utilized to establish a soil moisture gradient from a high-moisture regime receiving both irrigation water and rainfall to a dryland regime receiving only rainfall. In 1986, a second study was carried out to examine the effect of soil moisture at three locations that differed in annual precipitation. Plant emergence and harvestable tillers were reduced by C. sativus in both studies as compared to the noninoculated controls. Grain yield loss was associated with C. sativus and low plant density under drought but not under moderate to high moisture conditions. In the irrigated moisture regimes, moderate and high rainfall locations, the inoculated plants compensated for reduced plant stand and harvestable tillers by producing heavier kernels. Disease severity, based on the subcrown internode lesion development during the soft dough growth stage, did not differ in the dryland and irrigated moisture regimes. However, disease severity was higher in the drought location than in the moderate and high rainfall locations. Prolonged drought and disease pressure during seedling development can result in grain yield reductions, whereas subsequent moisture will affect the crop's ability to compensate for common root rot. Key words: Hordeum vulgare, ranking and selection, canopy temperature