Fungal growth is affected by and affects pH and redox potential (Eh) of the growth medium

Abstract

Fungal plant pathogens live in the specific environment of plants. Understanding of the interaction between pathogens and their host plants might open new ways to control plant diseases. Yet, the specificities of the plant environment and its effects on fungal growth are not yet fully explored. Both pH and Eh play a key role during the interaction between the fungus and its host plants, but often studied independently or at different scales. To decipher the interrelation between plant growth and their soil environment, recent theoretical and methodological advances have been made through the joint characterization of the pH and Eh. This opens the prospect to develop similar methods for fungi. The aim of our study was to investigate whether the methods developed for soil could be transposed to fungi. We first worked on artificial media, assessing the impact of fungal growth on the media in cultures. The growth of all 16 species tested significantly altered either Eh, pH or both in agar media. Measuring Eh reveals that even the species not modifying pH can have an impact on the surrounding environment. Reciprocally, altered media were used to characterize sensitivity of fungal growth to both pH and Eh parameters. The response of the six fungi tested to the modified media was quantitative with a decrease in colony diameter. In addition, colony aspect was repeatedly and thoroughly modified. As a first step towards the same studies in conditions matching the natural environment of fungal pathogens, we tested how the measurement can be performed with fungi growing on oilseed rape plants. In infected plant stems, pH and Eh were significantly altered, in opposite directions for L. maculans and S. sclerotiorum. The observed alcalinisation or acidification correlates with canker length. Our series of experiments indicate that the procedure published for Eh and pH in soil can be extended for measurement in agar media and in infected plants. Further, the joint characterization of both parameters opens the way to a more precise understanding of the impact of fungi on their environment, and conversely, of the environment on fungal growth. The availability of methods for measurement opens the prospect to study combinations of stresses, either on agar media or in plants, and get an understanding of the involvement of pH and Eh modifications in these interactions.

Comparative analysis of rhizosphere soil physiochemical characteristics and microbial communities between rusty and healthy ginseng root

“…Also, Acidobacteria subgroup 6 and Gemmatimonadetes emerged as the keystone taxa in HG rhizosphere soils, and they may play an important ecological role by degrading polysaccharides of plant and fungal origin 46,47 . These differences could be partially due to the different physicochemical characteristics of the two soils 48 . Fungal plant pathogens live in a specific environment, and the GRR rhizosphere soil environment may be more suitable for the survival of pathogenic fungi such as Ilyonectria.…”

The study of pH effects on contaminated fungal growth dynamics of date palm tissue culture

“…Also, the fungi differ in their pH requirements, despite their ability to grow across a wide range. (Landraud et al 2013;Bousset et al 2018). pH levels play a regulatory role in fungal virulence genes and stimulate mycotoxin release.…”

“…Consequently, pH alterations directly impact traits of explants and microorganisms, either positively or negatively. (Leifert et al, 1992;Bousset et al, 2018).…”