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Influence of pH and Matric Potential on Sporulation of Cephalosporium gramineum. Timothy D. Murray, Associate professor, Department of Plant Pathology, Washington State University, Pullman 99164-6430; C. Campbell Walter, agricultural research technologist, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Phytopathology 81:79-84. Accepted for publication 2 August 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-79.

Sporulation by Cephalosporium gramineum on mineral salts agar (MSA) containing phosphate or citrate-phosphate buffer, respectively, was 10-fold and 104-fold greater at pH 4.5?5.5 than at pH 6.5?7.5, regardless of temperature (MSA-phosphate buffer only) or fungal isolate. Sporulation on MSA with phosphate buffer was greatest at 20 and least at 5 C, which corresponds to the temperatures for greatest and least hyphal growth, respectively, on this medium. Sporulation on oat kernels artificially colonized by C. gramineum or on naturally colonized wheat straw, on or buried 2 cm below the soil surface, was twofold to threefold greater at soil pH 4.5?5.5 than at 6.5?7.5. In contrast to the effect of temperature in vitro, sporulation by C. gramineum on oat kernels on soil was 28-fold to 50-fold greater at 5 than at 15 C. Sporulation on oat kernels or straw on soil increased from twofold to 103-fold as soil matric potential decreased from ?0.001 to ?0.07 MPa. Greater sporulation of C. gramineum at low soil pH may partially explain why Cephalosporium stripe is more severe in acid soils (pH 4.5?5.5) than in soils of higher pH. However, the influence of soil matric potential on sporulation observed in this study was not consistent with the increase in Cephalosporium stripe at high soil moisture contents.

Additional keywords: inoculum production, Triticum aestivum, vascular wilt.