During the propagation and cultivation of pot plants, plant pathogenic bacteria and fungi can cause serious
problems, including plant death. In this study, biostimulatory products were investigated. Influence of three biostimulants and the fungicide Metalaxyl-M on expression of twenty-four genes of Arabidopsis thaliana infected by Botrytis cinerea or Phytophthora capsici was analyzed.
Addition of salicylic acid caused upregulation of genes important in jasmonic acid pathway, making the plant less susceptible to Botrytis infection. Chitosan upregulated an expression of genes that are involved in the salicylic acid route, making the plant less susceptible to Phytopthora infection. Interestingly, use of Metalaxyl-M resulted in a down regulation of plant defense genes.
In addition, we tested the influence of six biostimulants on development of disease symptoms of Fusarium foetens in Begonia and P. nicotianae in Kalanchoe in greenhouse experiments. Significant suppression of Phytophthora symptoms in Kalanchoë was observed in salicylic acid and silicon treatments. Decrease in disease occurrence was 60% and 87% for salicylic acid and silicon treatments, respectively. In the Begonia trial, no suppression against Fusarium foetens was obtained with any of the biostimulants. NMR analyses of plant compounds showed that in Kalanchoe plant compounds differed when compared to the other treatments when treated with silicon or chitosan.
A direct toxicity assay with aid of dual plate techniques showed an inhibition of Phytophthora as well as Fusarium with Streptomyces, while salicylic acid showed an inhibition of Fusarium only. Since silicon showed a clear effect on Phytophthora in Kalanchoe, an effect was visualized by NMR plant compound analyses and no direct toxicity towards the fungus was demonstrated, we may conclude that a plant response is the expected mode of action.
Sponsor of the research: Productschap Tuinbouw