The genotype-dependent effects of biologicals on drought adaptation in spring barley

Frequent periods of drought stress are causing significant challenges for agriculture worldwide. Given the global importance of drought stress, the use of biological plant growth agents (hereinafter referred to as “biologicals”) is being discussed as a potential approach to enhance the drought tolerance of plants. However, there is currently limited empirical evidence supporting positive effects of biologicals, and their mode of action is still largely unknown. In this study, eighteen biologicals were tested for their effects on early drought stress tolerance in two spring barley genotypes. Eight biologicals (Alginure, ASL Kombi Power, CropCover, ErosionControl, Burdock, Giant knotweed, FytoSafe, and Bioplantol mycos V forte) showed positive effects on six traits in one genotype and on seven traits in another genotype under early drought stress compared to the untreated control. Four biologicals were selected for validation trials with ten genotypes in greenhouse and field experiments. Thereby, grain biomass under drought stress was significantly (P < 0.05) increased by the biological Giant knotweed under both conditions. This study provides valuable insights into the genotype specific effects of biologicals and introduces a potential strategy for managing drought stress. Moreover, the results offer a better understanding of the effects and mechanisms of biologicals on abiotic stress in barley.