The Assessment of an Effect of Natural Origin Products on the Initial Growth and Development of Maize under Drought Stress and the Occurrence of Selected Pathogens

Abstract

Poland, like other countries in the world, increasingly experiences the ongoing climate change that is a critical yield-limiting factor. The use of biostimulants in agriculture has shown tremendous potential in combating climate change-induced stresses such as drought, temperature stress, etc. They could be a promising tool in the current crop production scenario. Biostimulants are organic compounds, microbes, or amalgamation of both that could regulate plant growth behavior through molecular alteration and physiological, biochemical, and anatomical modulations. They can promote plant growth under various environmental stresses because they have a positive effect, in particular, on plant growth and resistance. There are many products of this type available on the market, including those of natural origin, which are part of the Integrated Pest Management. The ecotoxicity of chemical plant protection products, the negative effects of their use, and the change in regulations make it recommended to use low-risk chemicals and non-chemical methods, that involve the least risk to health and the environment, and at the same time ensure effective and efficient protection of crops. Natural origin biocomponents obtained by the supercritical CO2 extraction of plant material or by fermentation process in bioreactors were tested. Common maize (Zea mays L.) was selected as a test plant for growth tests at climate chambers. Results showed that the only supernatant (fermentation broth) obtained with the Paenibacillus bacteria (S2) had a positive effect on the germination index (GI > 100%) of maize seeds, compared to the obtained plant seed extracts from the crop of the legume family (Fabaceae) (E3) and from the crop of the smartweed family (Polygonaceae) (E9) (GI < 100%). The extracts E3, S1 (supernatant obtained with the use of bacteria from the genus Enterobacter) and S2 used as a single product and in combination with UAN+S, under optimal conditions of the experiment, had a positive effect on the maize root weight compared to the untreated, while under drought stress, a decrease in the root weight was observed. Moreover, on the basis of the conducted research, differences in the mycelial growth of selected fungi were found. The applied biocomponent S2 of microbial origin extract (supernatant 2) showed a mycelial growth-limiting effect on all tested Fusarium fungi isolated from the corn cobs.