Survival of the sclerotia of Phymatotrichopsis omnivora as a function of pH in vitro

Abstract

Phymatotrichopsis omnivora is a phytopathogenic fungus that attacks thousands of species of plants, mainly in alkaline soils. In this study, we assessed the capacity of sclerotia of P. omnivora to change the pH and survive in acidic and buffer solutions. The sclerotia were placed in acetic (0.4, 0.8 and 1.7 mmol L-1) and sulfuric acid solutions (0.25, 0.5 and 1 mmol L-1) for two weeks; these solutions were not replaced or were remade one, two or three times. The sclerotia were also put in buffer solutions for seven days (pH 4, 5, 8 and 9), undiluted or diluted at 1:2, 1:4 and 1:10 v/v. Other sclerotia were placed in selected solutions of 0.5 mmol L-1 sulfuric acid and in buffer solutions with pH 5 diluted 1:10; they were then extracted and subjected to stress treatments. These treatments consisted in placing the sclerotia in: NaOCl solution, sand saturated with glucose, f looded sand, and sand at field capacity. The sclerotia changed the pH of the acetic acid solutions without replacement, and the Ph of buffer solutions with pH 8-9 diluted 1:10. However, the change of pH of the solutions was marginal when the acids were not replaced and when the buffer solutions were not diluted. The survival of the sclerotia was null with three replacements of sulfuric acid at 1 mmol L-1 and in buffer solutions with pH 4 and 5 diluted 1:4 or less, and with pH 9 undiluted; some sclerotia survived in the rest of the solutions. Stress treatments had a synergistic effect of reducing the survival of sclerotia that had been previously placed in the selected solutions (0.5 mmol L-1 sulfuric acid and buffer with pH 5 diluted 1:10).