Effect of Seed Dressing and Soil Chemical Properties on Communities of Microorganisms Associated with Pre-Emergence Damping-Off of Broad Bean Seedlings

Abstract

Combating soil pathogens that disable plant emergence is among the most difficult challenges of global agriculture. Legumes, preferred in sustainable cultivation systems, are particularly sensitive to pre-emergence damping-off of seedlings. Seed dressing is therefore a very important element in the cultivation technology. The aim of this study was to compare the impact of biological (Pythium oligandrum) and chemical (carboxin + thiuram) seed dressing on the quantitative and qualitative composition of microorganisms participating in the epidemiology of this disease, under specific hydrothermal conditions and chemical properties of the soil (pH, humus, macro-, and micronutrient). Microorganism identification was done using the MALDI-TOF MS (Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry) technique. Species were assigned to frequency groups, and populations of pathogens, saprophytes, and antagonists were identified. The biodiversity of these communities was expressed with Simpson’s Reciprocal, Shannon–Wiener, and Evenness (Shannon) indices. In individual variants of seed pre-treatment, the correlations between individual edaphic factors and the suppression of pre-emergence damping-off, the number of isolates obtained from infected seedlings, and the share of individual trophic groups of fungi were assessed. The main causes of pre-emergence damping-off of broad bean seedlings are Ilyonectria destructans, Globisporangium irregulare, Fusarium equiseti, Rhizoctonia solani, and Fusarium solani. Eliminating seed treatment results in a seedling mortality rate of 33.5%–42.5%. The effectiveness of the chemical protection product is 44.2% and 25.9%. Carboxin and thiuram reduce the diversity of microorganisms involved in the pathogenesis of pre-emergence damping-off and limit the presence of antagonistic fungi. Under the influence of P. oligandrum, there was a five-fold increase in the population of antagonists. An increase in humus in the soil reduces the percentage of diseased broad bean seedlings.

Health Parameters of Potato Tubers under the Influence of Soil Applied Bio-Preparations and Bio-Stimulants

“…The representative of the kingdom of Chromista (class Oomycetes), Pythium oligandrum, is one of the best-known organisms used in plant protection for the longest [43,44,95,96]. According to Brozowa [97], P. oligandrum contributes to an increase in the soil population of antagonists, which reduces the density of many important pathogens, including R. solani.…”

“…Knowledge of the causes of diseases is crucial for the successful management of potato production. In practice, the fight against pathogens living in soil and carried with seed potatoes is not easy [20,21,30,32,[40][41][42][43][44]. It should be highlighted that the use of chemical protective agents may be ineffective if environmental conditions promote the dispersion of pathogens or if fungicide-resistant genotypes appear [45][46][47].…”

“…It should be highlighted that the use of chemical protective agents may be ineffective if environmental conditions promote the dispersion of pathogens or if fungicide-resistant genotypes appear [45][46][47]. The use of synthetic pesticides has numerous times been shown to lead to a loss of soil biodiversity and an accumulation of pathogenic bacteria, fungus-like organisms, and fungi in soil [42][43][44]48]. The introduction of organic matter to soil is one of the more effective methods of restoring soil biodiversity and balance between populations of beneficial and pathogenic microorganisms [42,49,50].…”