pH regulates the pathogenicity and extracellular enzyme activity of Gilbertella persicaria on pitaya fruit.

pH is an important environmental factor affecting the pathogenicity of many fungi. The pH change in the decayed tissue of pitaya fruit inoculated with Gilbertella persicaria, the kinds of organic acids secreted by G. persicaria, the effects of three ambient pH values on pathogenicity, and the activities of pectinase and cellulase in pitaya fruit were studied. The results showed that colonization of pitaya fruit by G. persicaria was accompanied by local acidification of the host tissue, with the pH decreasing from 4.76 to 4.41. The main organic acid secreted by G. persicaria was oxalic acid, followed by citric acid. Furthermore, pH 4.4 enhanced the activities of pectin methylesterase (PME), polygalacturonase (PG), pectin methyl polygalacturonase (PMG) and pectatelyase (PL), as well as cellulase (Cx) and β-glucosidase (β-Glu), in pitaya fruit. Our results indicate that ambient pH is a regulatory factor for the pathogenicity of G. persicaria infecting pitaya fruit, and this study will aid in the development of new methods to control fruit decay caused by G. persicaria. [ABSTRACT FROM AUTHOR]