Influence of pH on Cephalosporium gramineum. I. Radial growth and dry matter accumulation

Abstract

Radial growth of three isolates of Cephalosporium gramineum was fastest at or below pH 6.0 and slowest at pH 7.5 at 20 °C on corn meal agar and mineral salts agar adjusted to pH values from 4.5 to 7.5 with either phosphate or citrate–phosphate buffer. Interactions among medium, pH, buffer, and isolate occurred. On media containing phosphate buffer, growth occurred over the entire range of pH and was maximal at pH 5.5, but on media containing citrate–phosphate buffer, growth was maximal at pH 4.5, with little growth above pH 6.5. Dry matter accumulation was greatest at pH 4.5 and least at pH 7.5 in mineral salts broth buffered with phosphate or citrate–phosphate buffer. The water potential of media buffered with citrate–phosphate buffer was lower than that of media buffered with phosphate buffer, but these differences only partially explain the observed growth responses. Growth of C. gramineum occurred from 5 to 25 °C, but it was fastest at 20 °C. In general, temperature did not influence the qualitative response of C. gramineum to pH. The pH range most favorable to growth in vitro corresponds to the range of soil pH most favorable to development of cephalosporium stripe disease in the field and greenhouse; this may help explain the increased incidence of disease through increased inoculum potential.