Evaluation of the effects of biostimulant substances on Avena sativa, Vicia faba, and Olea europaea

Enhancing crop performance through sustainable and efficient methods is an increasingly important goal in modern agriculture. Among the tools explored to achieve this goal, biostimulants have gained growing attention for their ability to influence plant physiology, improve growth, and increase tolerance to environmental stress. Unlike fertilizers or pesticides, these substances act indirectly, often by stimulating natural plant processes. This study evaluates the bioactivity of several experimental formulations, applied as foliar sprays, on three plant species of agronomic importance: Vicia faba (broad bean), Avena sativa (oat), and Olea europaea (olive tree). These species were selected not only for their agricultural relevance in Southern Europe, but also for their contrasting biological traits, Vicia faba as a nitrogen-fixing legume, Avena sativa as a fast-growing cereal, and Olea europaea as a perennial woody species. The tested substances were applied as foliar treatments in different formulations, composed of either single or multiple components. Some of these included a Blad-containing oligomer (BCO), applied alone or in combination with other active ingredients, due to its known biostimulant and antifungal properties. All substances were provided by an industrial partner, and their detailed composition remains confidential. The experimental work was carried out in three main phases. The first phase consisted of the cultivation of the three species and the application of the treatments. Vicia faba and Avena sativa were grown in pots under greenhouse conditions and treated with five formulations, applied foliarly three times per week starting from the third week after sowing. Olea europaea trees (cv. Galega Vulgar), aged seven years and grown in pots under outdoor conditions, were treated with seven formulations, partially overlapping with those used for the herbaceous species, and sprayed twice weekly for three weeks. Two control groups were included for each species. The second phase involved the evaluation of physiological and morphological parameters. In broad bean and oat, parameters included NDVI and PRI reflectance indices as proxies for chlorophyll content and photosynthetic efficiency, shoot and root length, dry biomass, and the presence or absence of nodules in Vicia faba. In olive, NDVI and PRI measurements were also taken to monitor the photosynthetic state of the plant. In the third phase, olive trees were artificially inoculated with a virulent strain of Colletotrichum godetiae, the fungal pathogen responsible for olive anthracnose. Symptoms development was monitored, and pathogen identity was confirmed by re-isolation from infected fruits. The study revealed species-dependent responses to the formulations, with some treatments showing measurable effects on selected parameters. In olives, although physiological differences among groups were limited prior to inoculation, differences in the percentage of infected fruits were observed later on in the growing season. The results suggest potential biostimulant activity and a possible contribution to disease mitigation. These findings represent a basis for further investigation into the mechanisms of action of the tested substances and their application in different plant systems, including liquid cultures and integrated strategies aimed at improving crop performance and resilience. This work is also a very first insight for further studies on olive anthracnose management strategies.