Inactivation of the Plant Pathogen Pythium ultimum by Plasma-Processed Air (PPA)

Abstract

Pythium species are saprophytic or facultative plant pathogens that cause a variety of diseases. Usually, chemical anti-fungal seed dressing is applied in the conventional pre-harvest for seed protection. Nevertheless, recent legislative rules have created a ban on certain agrochemicals. Therefore, alternative eco-friendly methods have to be identified to ensure healthy field emergence and seedling development. In this study, a proof-of-concept was performed on the inactivation of Pythium ultimum Trow mycelia grown on potato dextrose broth agar (PBA) by plasma-processed air (PPA). Different plasma process parameters were applied using variation in gas flow of air through the microwave plasma generator and PPA exposure time. The PPA treatment was compared to the untreated and gas treated controls. The results showed a complete inactivation of P. ultimum mycelia after the PPA treatment. Inactivation efficiency was independent of the gas flow parameter and even shorter exposure times resulted in complete inactivation. To fully evaluate the potential of PPA as a possible seed hygiene measure, tests regarding the inactivation of P. ultimum after artificial inoculation onto seeds and/or studies using naturally infected seeds should be performed. This may be accompanied by monitoring the disease severity after the PPA treatment on a field scale.

Exploring Microbial Rhizosphere Communities in Asymptomatic and Symptomatic Apple Trees Using Amplicon Sequencing and Shotgun Metagenomics

“…On the other hand, Pythium species are extensively spread as plant pathogens, including several apple pathogens [98]. However, other members of this genus are prevalent as soil saprophytes [99] and have been identified as exhibiting saprophytic behavior in soil samples, with distribution influenced by factors such as soil type, precipitation, and temperature. Hence, it is crucial to emphasize that not every Pythium species is pathogenic.…”