Abstract
The ascomycete fungus Microdochium nivale is a major pathogen of many species of the gramineae. Control measures rely heavily on chemical fungicides, making alternative means of disease reduction desirable. Phosphite (PO33−), has proven efficacy in reducing susceptibility of different species of gramineae to oomycetes, and has adverse effects on the in vitro growth of numerous other pathogens. The effect of phosphorous acid (H3PO3), phosphoric acid (H3PO4), dihydrogen potassium phosphite (KH2PO3), dihydrogen potassium phosphate (KH2PO4) and potassium hydroxide (KOH) on the in vitro mycelial growth and development of M. nivale was determined. Radial growth on amended potato dextrose agar (PDA) was used to calculate mean daily growth and percentage inhibition. PO33− had a significant inhibitory effect on mycelial growth, with EC50 values ranging between 35.9 and 40.99 μg mL−1, whilst PO43− and KOH had no significant inhibitory effect. Microscopic examination of mycelia showed morphological deformities in hyphae growing on PO33− amended PDA, whilst hyphal growth was normal on PO43− and KOH amended PDA. Conidial germination of M. nivale was significantly reduced following immersion in solutions of 50, 100 and 250 μg mL−1 of PO33−, while PO43− and KOH at the same concentrations induced no inhibitory affect. These results show that PO33− is a significant inhibitor of the growth of M. nivale and may have the potential to be used as a chemical control agent in the field.
Highlights
Suppression of M. nivale by phosphiteMicrodochium nivale (teleomorph Monographella nivalis (Schafnitt)) is an ascomycete pathogen and causal agent for many disease complexes in numerous graminaceous species (Smiley et al, 1992; Tronsmo et al, 2001)
Percent relative growth (PRG) rates of M. nivale grown on amended PDA were used to determine the percent inhibition
The majority of research with phosphite for controlling plant pathogens has been with oomycetes (Coffey and Bower, 1984; Smillie et al, 1989; Cook et al, 2005; Garbelotto et al, 2008)
Summary
Microdochium nivale (teleomorph Monographella nivalis (Schafnitt)) is an ascomycete pathogen and causal agent for many disease complexes in numerous graminaceous species (Smiley et al, 1992; Tronsmo et al, 2001). M. nivale is regarded as the most damaging pathogen of temperate climates, infecting and causing disease in most cool season species, causing pink snow mould and microdochium patch (Vargas, 2005). While phosphite is registered as a fungicide in some legislations, in many it is regarded as a biostimulant. It is the alternative mode of action in suppressing numerous plant pathogens that is of interest here
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