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Show The Effect of pH on Two Strawberry Root Rot Fungi' By F. B. W ANN and B. L. RICHARDS2 Strawberry root rot is a disease which apparently involves a number of inhabiting fungi. In a previous paper before this body, Richards and McKay3 discussed some of the general economic and symptornological aspects of this disease and reported on the results of isolation and inoculation studies, which showed that a number of common soil organisms are present in diseased roots and can produce lesions on healthy roots. In an effort to arrive at a clearer understanding of the etiology of this disease complex, certain physio logical studies of the isolated fungi were inaugurated. This paper reports some of these preliminary experiments on the effect of the H-ion concentta tion on growth of two of the root rot organisms. soil Method Two species of Fusarium--F. orthoceras and F. solam-were used. The fungi were grown in erlenmeyer flasks in a standard mineral nutrient solution, with glucose as a source of carbon. Each culture was supplied with 50 cc. of nutrient solution. The various cultures differed only in H-ion concentration, which was maintained by the use of phosphate buffers. At the end of a grow ing period of 16 days, the mycelial mats were harvested by filtering off the solutions through weighed Gooch crucibles provided with asbestos mats. The crops were dried at 100°C. for twenty-four hours, then weighed. Results Experiment 1. Fusarium orthoceras was used in this experiment, The dry weights of the crops produced in solutions ranging in pH from 3.4 to 6.5 were very uniform, averaging about 75mg. in weight. At pH 6.S there was an increase in growth to 10Smg., followed by a drop at pH 7.2 to 74 mg. A second rise in weights occurred in the more alkaline solutions, reaching a maximum of 138 mg. at pH 9.2. Experiment 2. The experiment was repeated with the same organism and with quite similar results. Two maxima of growth occurred, one at pH 6.8 with 178 mg. dry weight, and the second at pH 9.2 with 110 mg. The crops produced in the range from pH 3.4 to 5.9 were fairly uniform, averaging about 65 mg. From these two experiments it is obvious that there is double maximum in the growth of this organism when dry weights are plotted against the pH of the nutrient medium. Experiment 3. In this experiment Fusarium growth in all cultures ranging from pH 3.4 to 9.2 solani was was used. The quite uniform, the Contribution from the Department of Botany and Plant Pathology, Utah Agricultural 2 3 Experiment Station. Associate Plant Physiologist and Botanist and Plant Pathologist, respectively. Utah Academy of Arts, Science and Letters Authorized for publication by the Director. 45 13: 17, 1936. |
