Abstract

Rhizoctonia bataticola, the root-rot pathogen of groundnut readily utilized L-phenyl- alanine, L-tyrosine and DL-tryptophan when either substituted as nitrogen source or suppli- mented in Czapek's medium. In the tryptophan supplemented medium indoleacetic acid was measured; the quantity of IAA synthesised considerably varied with incubation time and also with the amount of precursor fortified in the medium. Several phenolic substances were detected in the culture filtrate. Like IAA, ammonia in the culture filtrate also varied with incubation time. Phenylalanine ammoniatyase (PAL-ase) activity was detected in the culture filtrate of the medium which received phenylalanine. But, no tyrosine-deaminase was detected in tyrosine fortified medium. The role of these amino acids in the biosynthesis of IAA and phenols by R. bataticola is discussed.

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