Differential effects of yeast derivatives on pepper productivity, stress resilience, and soil microbial communities

The excessive application of chemical fertilizers is a prevalent issue in modern agriculture, as it increases production costs, undermines economic returns, and degrades soil health. In this study, the effects of two compositionally distinct yeast derivatives, namely Yeast Glycoside Type I (YD1) and Water-Soluble Yeast Glycoside (YD2), on the growth, nutrient use efficiency, low-temperature (LT) stress tolerance, and rhizosphere microbial communities of pepper (Capsicum annuum L.) were investigated. The yeast derivatives (YD) were characterized using scanning electron microscopy (SEM) and biochemical analysis, which revealed distinct profiles: YD2 contained higher nitrogen (11.89%), isindole-3-acetic acid (IAA), and 1-Aminocyclopropane-1-carboxylic acid (ACC), whereas YD1 was enriched in cytokinins (isopentenyl adenine, iP; trans-zeatin, tZ). Under normal temperature (NT) conditions, application of YD2 at concentrations of 1% significantly enhanced pepper yield, shoot biomass, and nitrogen/potassium use efficiency, whereas YD1 exerted minimal effects. However, under low-temperature (LT) stress, applications of YD1 and YD2 did not significantly increase yield. Despite this, YD2 maintained root activity, mitigated chlorophyll degradation, and increased the activities of antioxidant enzymes under LT stress. Both YD altered rhizosphere bacterial community structure under NT conditions (PC1: 42.09%, p = 0.007); however, this effect was attenuated under LT stress (PC1: 24.85%, p = 0.003). Specifically, YD1 was associated with an increased relative abundance of Microscillaceae (NT) and Thiobacillus (LT), while YD2 was linked to an increase in Kaiserbacteria (NT) and Armatimonadales (LT). These findings suggest that the two YDs, particularly YD2, can influence pepper productivity and stress resilience through associations with improved nutrient uptake, physiological adjustments, and shifts in the rhizosphere microbiome. This pot-based study provides insights into the potential of tailored yeast derivatives as biostimulants, offering a basis for developing more sustainable agricultural practices.