###### Abstract  
Biostimulants are the next-generation choice for sustainable agricultural production and are gradually becoming an alternative to synthetic chemicals. Various botanicals are proposed to exert stimulatory effects, and garlic allelochemicals are among such botanicals; however, a peer-reviewed scientific evaluation is required to understand garlic-derived substances such as biostimulants. Current studies were therefore performed to identify the bioactivity of garlic extract as a biostimulant to improve crop quality, alter its physiological potential, and prime its defense responses against pathogenic fungal infections. 100 \(\mu\)g mL\({}^{-1}\) aqueous garlic extracts (AGE) in consort with 1 mM of acetyl salicic acid (ASA) and distilled water as a control treatment were applied to eggplant and pepper seedlings as foliar application and fertigation methods. The results revealed stimulatory responses in the growth of the vegetables with improved plant height, number of leaves, root growth, fresh and dry weight, etc., due to AGE and ASA applications. Moreover, significant alterations were indicated in plant metabolites such as chlorophyll, carotenoids, and soluble sugars. Additionally, stimulation of the antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD), as well as the root activity of these plants, was observed after treatment. Application of AGE and ASA also exerted priming effects on pepper plants, inducing defense responses prior to _Phytopthora capsici_ inoculation, and the treated plants therefore successfully resisted infection through activated antioxidant systems, and probably carotenoid and other protectory metabolites. Stress-induced H\({}_{2}\)O\({}_{2}\) content was extremely low in the treated plants, indicating successful resistance against pathogenic infection. Keywords:aqueous garlic extract; biostimulant; H\({}_{2}\)O\({}_{2}\); defense priming; SOD; POD; carotenoids; _Phytopthora capsici_; disease resistance +
Footnote †: journal: Applied Soft  
production cannot be overlooked [1; 2]. However, due to its enclosed environment, the increase in humidity and fluctuations in the temperature often cause favorable conditions for the phytopathogens, which may seriously impair crop production [3]. To ascertain the safety of plants and safeguard against these phytopathogens, various synthetic chemicals are widely used in these production units. In the long run, however, these chemicals pose a serious threat to human health due to their hazardous outcomes [4]. Nonetheless, the demand from the consumers for greener produce and organic foods has increased recently. Therefore, scientific communities must try to find alternatives to these synthetic chemicals to ensure the production of safer and more environmentally friendly horticultural production. Agricultural biostimulants, for instance, could be considered a reasonable alternative. These biostimulants include diverse formulations of compounds, substances, and micro-organisms that are applied to seeds, plants or soils to improve crop vigour, yields, quality, and tolerance to abiotic stresses. Various organic compounds have been identified as biostimulants that enhance crop quality, improve physiology, or activate disease resistance in the receiver plants [5; 6]. In a recent study, gelatin used as solid capsules placed beside seeds during germination, stimulated the growth and development of cucumber by providing nitrogen [7]. On the other hand, the biostimulation of soy flour as a seed coating considerably improved the root and shoot growth of broccoli seedlings after germination [8]. Apart from animal- and plant-derived biostimulants, numerous seaweeds have been reported to improve plant growth due to their biostimulation potential. A homogenate from Baltic seaweeds was shown to have improved the seedling vigour and growth of radish [9].