Amino acid changes during the early stages of tomato wilt disease (Verticillium albo-atrum)

Soil-borne pathogens such as Verticillium species, invade into the roots of many herbaceous and woody hosts. The xylem environment supplies these pathogens with a continuous flow of nitrogen-rich nutrition. Detailed quantitative increases in amino acids in the stems, petioles, leaflets and roots of young tomato plants infected with Verticillium. albo-atrum the causal agent of wilt disease, are described in this paper for the first time. Results focus in particular on the vascular environment prior to the emergence of visual symptoms. Total amino acid concentrations in infected stems and petioles increased substantially at 144 and 216 h after inoculation. This effect was evident in leaflets at 216 h after inoculation. By 216 h most amino acid concentrations were substantially increased in stems, petioles and leaflets of infected plants relative to healthy controls. Earlier at 144 h in stems substantial increases were recorded for aspartic acid, threonine, serine, glutamic acid, glycine and ethanolamine. A similar picture emerged for petioles with the addition of increases in proline but not glycine. Amino acids increasing substantially in infected leaflets at 216 h were aspartic acid, glutamic acid and ethanolamine. In the infected roots there was relatively little difference in amino acid concentrations relative to healthy controls with the particular exceptions of proline and ethanolamine. By 18 days (432h), when visual symptoms were well advanced marked increases in amino acid concentrations were found for threonine, serine, α-alanine, valine, methionine, iso-leucine, leucine, tyrosine, ethanolamine, ornithine, lysine, histidine and arginine.