The Effect of some Amino Acids on the Growth of Two Varieties of Ophiobolus graminis

SUMMARY: An examination was made of the effect of certain amino acids on the growth of three isolates of Ophiobolus graminis Sacc. and of six isolates of 0. graminis var. avenue, either as sole sources of nitrogen, or as supplements to ammonium nitrate. In all cases growth with aspartic acid was equal or nearly equal to that obtained with hydrolysed casein. Lysine and threonine were strongly inhibitory. The two varieties differ from each other in their reaction to cystine and cysteine, 0. graminis itself making as good growth with these amino acids as with hydrolysed casein, and var. avenae being inhibited in growth. Ophiobolus graminis Sacc. var. avenae differs from 0. graminis itself in patho-genicity, being capable of causing a root rot (take-all) in oats as well as in wheat, in ascospore length, and in its capacity to make good growth in expressed sap from oat roots which does not support growth of 0. graminis. The two varieties resemble each other closely in general morphology, in the type of infection and development of the disease in wheat, and in sensitivity to an inhibitor of growth and respiration obtained from oat sap (Turner