Mycelium growth of early tomato blight pathogen, Alternaria solani, subjected to high dilution preparations

This study investigated the effect of high dilution preparations on the development of Alternaria solani mycelium, which causes early blight on tomato plants. Twelve bioassays were conducted under controlled conditions. Colony discs, 0.7cm diameter, of A. solani were transferred into Petri dishes containing potato dextrose agar (PDA) or PDA+V8((R)) vegetable juice media. High dilution preparations of Arsenicum album, Nitricum acidum and Staphysagria at 6, 12, 25, 30, 50, 60, 80 and 100CH (centesimal Hahnemannian dilution scale) were applied either over the media or mixed in with it. Results showed that high dilution preparations have different effects on A. solani mycelium growth, according to the dynamization level. A. solani colonies were reduced by A. album 80CH, by N. acidum 80 and 100CH, and by Staphysagria 6, 30 and 60CH compared with the control when applied over PDA medium. Higher mycelium reduction was observed in the PDA assays when the treatments were applied over the medium than when incorporated into it. The differences among high dilution treatments were distinctly greater on the PDA medium than on the PDA+V8((R)). Bioassay is a suitable method for screening high dilution preparations before studying them under field conditions.