Studies on the effect of exogenous amino acid application on nematodes

Abstract

Plant parasitic nematodes are considered as key pathogens in agricultural crop production. They cause substantial yield losses in numerous crops and across all climatic regions worldwide. Antagonistic effects on various life stages of economically relevant plant pathogenic nematode species were reported for different amino acids (aa). In order to screen for effects induced by exogenous application and to reveal their underlying mechanistic methionine (Met), lysine (Lys), threonine (Thr), isoleucine (Ile), 2-ketobutyric acid (Ket), homoserine (Hom) and tryptophan (Trp) were tested on the free-living nematode <em>Caenorhabditis elegans</em> and the plant parasite <em>Heterodera schachtii</em>. <br /> Try applications reduced the activity and development of <em>C. elegans</em>, whereas only Ket affected the activity of <em>H. schachtii</em>. Interestingly, soaking J2 stage nematodes in aa solutions for twenty-four hours, induced a sex ratio change for both Lys isomers. The strongest effects were observed when aa were supplemented to the nutrient-medium in a monoxenic culture of the host plant, <em>Arabidopsis thaliana</em>. This approach reduced the number of female nematodes per plant for Iso, Met, Thr, and Ket. Additionally, slight negative effects could be detected on the adult female sizes. Interestingly, these effective aa all belong to the aspartate pathway. Herein, in particular the plant inherent enzyme methionine-γ-lyase (MGL) was identified as possible key functional element.