METABOLITE CHANGES INDUCED BY CUCUMBER MOSAIC VIRUS IN RESISTANT AND SUSCEPTIBLE STRAINS OF COWPEA

Cucumber mosaic virus infection of both resistant (local lesion) and susceptible strains of cowpea (Vigna sinensis) resulted in an increase of most of the amino acids, especially asparagine, that were recovered 2 days after inoculation. Pipecolic acid was found only in the infected resistant strain of cowpea. Exposure of plants to C14O2 for 4 hr prior to harvest resulted in an increased labeling of the amino acid and organic acid fractions of the infected tissue. Radioactivity was detected only in aspartic acid, except for traces in asparagine in the infected tissue. Radioactivity of malic and malonic acids was greater in the infected tissue of resistant and susceptible strains, whereas an increase in labeled citric acid occurred only in the infected tissue of the susceptible strain. Phosphoenolpyruvate carboxylase activity increased 40 and 60% in infected resistant and susceptible strains of cowpea, respectively. An accelerated dark CO2 fixation can partly account for the increase of some organic acids, amino acids, and amides in infected plants.