Role of nutritional factors and light in the sporulation of two isolates of Myrothecium roridum

Abstract

Among single-spore isolates of Myrothecium roridum obtained from leaf spots on Croton sparsiflorus, some required light for sporulation on natural media while others sporulated in the dark. A dark-sporulating (DSP) isolate and a light-requiring one (LSP) were studied. Sporulation of the DSP isolate was also better in light. Amino acids were, generally, the best sources of N for this isolate. The LSP isolate failed to sporulate on a medium containing nitrate. This isolate, however, showed moderate sporulation, even in the dark, on a medium with cellulose as the C source and around the inoculum plug on a medium lacking C. Appreciable sporulation was seen in the LSP isolate when nitrate was replaced by casaminoacids or tyrosine. While tyrosine did not enable sporulation in the presence of nitrate, a few other aromatic compounds did. The aromatic nature of tyrosine, rather than its role as an N source, has been suggested as being responsible for its effect on the LSP isolate.