INHIBITION OF RUST DEVELOPMENT ON DETACHED WHEAT LEAVES BY METABOLITES, ANTIMETABOLITES, AND ENZYME POISONS

The effect of metabolites and antimetabolites on rust development was studied, using detached leaves of Little Club wheat floated on solutions containing benzimidazole plus the compound under study. Purines and pyrimidines, vitamins, amino acids, carbohydrates, and enzyme poisons were tested. A number of these compounds inhibited leaf and stem rusts of wheat at concentrations that were not injurious to the host. Of the purines and pyrimidines that were tested, thymine and the analogue azathymine were the only effective inhibitors. The antivitamin oxythiamine was inhibitory and the inhibition was competitively reversed by thiamine.A few natural amino acids, notably histidine, isoleucine, methionine, and serine, inhibited rust development. The inhibition was reversed by glycine in all cases except with serine. Amino acid analogues, particularly canavanine, ethionine, and p-fluorophenylalanine, were excellent inhibitors; the inhibitions were reversed by comparable levels of arginine, methionine, and phenylalanine respectively. The carbohydrates lyxose, xylose, sorbose, and all the sugar alcohols tested were effective inhibitors of rust development. Of the enzyme poisons tested, sodium fluoride and sodium azide differentially inhibited rust growth.