ROOT EXUDATES FROM RED PINE SEEDLINGS AND THEIR EFFECTS ON PYTHIUM ULTIMUM

Abstract

The role of root exudates in interaction between pine roots (Pinus resinosa Ait.) and Pythium ultimum Trow was studied. By paper chromatographic methods three sugars and 13 amino acids were definitely identified in the root exudate. Gamma amino butyric acid was most abundant, although asparagine, glycine, serine, and alanine were also present in large amounts. Valine, leucine, glutamine, aspartic acid, glutamic acid and proline were detected in smaller quantities. Among the sugars, both glucose and fructose were abundant while traces of arabinose were detected. When supplied singly, all amino acids and sugars except serine, leucine and arabinose, stimulated growth of the pathogen and germination of sporangia. Mixtures of sugars or mixtures of three or four amino acids were very effective in stimulating mycelial growth and development of germ tubes. The kind of nutrient influenced the number of germ tubes per sporangium. Favorable nutrient combinations, viz. mixtures of sugars, mixtures of three or four amino acids or root exudate solution, produced two to nine germ tubes, while unfavorable ones, viz., glycine, arabinose and serine, etc., produced one or two germ tubes.