Influence of the cyst nematode Heterodera schachtii on relative changes in the pattern of free amino acids at feeding sites

Abstract

A microanalytical method with sensitivity at the pmol level was used to study relative changes in the pattern of free amino acids at feeding sites of the sugar beet cyst nematode (Heterodera schachtii) on roots of oil radish (Raphanus sativus var. oleiformis) and rape (Brassica napus) grown in aseptic nutrient agar. Measurements were made on root segments 0·5 cm long containing the metabolically very active nurse cells (syncytia) produced at nematode feeding sites, on adjacent segments without syncytia and on corresponding segments of uninoculated roots.The method was shown to be reliable and was used to examine amino acid changes in host tissue at six stages of the female's development from early parasitism until death. It was essential to remove nematodes uninjured to obtain reliable assessments of changes occurring in host cells.Similar changes occurred in both host species. Glutamine and asparagine decreased significantly from the early stages of parasitism until the females had produced eggs. Other significant changes were restricted to a few amino acids at certain developmental stages only. For example, isoleucine, leucine, valine, phenylalanine and tryptophan increased during egg production by females. Changes in the pattern of free amino acids were the same in susceptible and resistant roots of oil radish up to 1 to 2 days prior to syncytium degeneration in resistant roots.