Seed exudates from Pinus resinosa and their effects on growth and zoospore germination of Pythium afertile

Abstract

The role of exudates from germinating seeds of red pine, Pinus resinosa Ait., was examined in relation to zoospore germination and growth of Pythium afertile Kanouse and Humphrey. By paper chromatography, 14 amino acids, 4 sugars, and 3 organic acids were identified in the seed exudate. Among the sugars, glucose, fructose, and sucrose were detected in large amounts and arabinose in small amounts. Of 14 amino acids identified, threonine, lysine, arginine, and glutamine were present in trace amounts; leucine, γ-aminobutyric acid, valine, asparagine, and alanine in large amounts; and proline, serine, glycine, aspartic acid, and glutamic acid in small amounts. Of three organic acids detected, malonic acid was most abundant whereas citric and fumaric acids were present in small and trace amounts, respectively.When supplied singly, all sugars and amino acids, except alanine, threonine, γ-aminobutyric acid, and arabinose stimulated mycelial growth and germ tube growth of P. afertile. Organic acids promoted no growth and inhibited zoospore germination. Mixtures of sugars and mixtures of three or four amino acids effectively stimulated growth of mycelium and germ tubes. One to three germ tubes were produced with certain amino acids and sugars but only one germ tube with others. There was no correlation between the percentage zoospore germination and length of germ tube.