The Effects of Papaya Ringspot Virus Infection on the Nitrogen Metabolism of Carica papaya L.: Part II. Composition of Free Amino Acids in the Leaves

Abstract

Leaves of mechanically inoculated Carica papaya L. plants with papaya ringspot virus (PRSV) were examined for free amino acids by using paper, thin layer and high pressure liquid chromatography (HPLC) techniques. Seven amino acids: aspartic acid, glutamic acid, serine, arginine, threonine, alanine and glycine were detected by paper and thin layer chromatography and another eight amino acids: histidine, methionine, isoleucine, leucine, lysine, tyrosine, valine and penylalanine were detected by HPLC. A two fold increase in the concentration of serine, alanine, arginine, threonine and aspartic acid was observed in the leaves infected with PRSV. Methionine, valine histidine and tyrosine contents in the infected leaves were decreased but no significant differences were found in the contents of glutamic acid, isoleucine and leucine, These changes were detected in the inoculated leaves as early as three hours of inoculation and same tendency was observed at the later stages of disease development. Similar changes in free amino acids were observed in the field plants naturally infected with PRSV, despite their age and different climatic conditions of growth.