SPORULATING POTENTIAL OF RHYNCHOSPORIUM SECALIS ON NATURALLY INFECTED LEAVES OF BARLEY

The period of time during which Rhynchosporium secalis retained its ability to sporulate in lesions of naturally infected leaves of barley was strongly influenced by an interrelationship of moisture, temperature, and location of leaves in relation to the soil. Saprophytic microbial invasion of scald lesions appeared to play a dominant role in terminating the sporulating potential of the scald fungus. Most rapid deterioration of the stroma occurred at 18 °C in continually moist conditions on leaves in contact with the soil. A second factor involved in the destruction of sporulating ability in lesions that escaped microbial deterioration depended on the depletion of food reserves of the stroma. This depletion was induced by the production of successive crops of conidia without observable new growth of the fungus. This latter factor operated under alternately wet and dry conditions.