Abstract
The increasing culinary use of onion (Alium cepa) raises pressure on the current production rate, demanding sustainable approaches for increasing its productivity worldwide. Here, we aimed to investigate the beneficial effects of licorice (Glycyrrhiza glabra) root extract (LRE) in improving growth, yield, nutritional status, and antioxidant properties of two high-yielding onion cultivars, Shandaweel and Giza 20, growing under field conditions in two consecutive years. Our results revealed that pretreatments of both onion cultivars with LRE exhibited improved growth indices (plant height and number of leaves) and yield-related features (bulb length, bulb diameter, and bulb weight) in comparison with the corresponding LRE-devoid control plants. Pretreatments with LRE also improved the nutritional and antioxidant properties of bulbs of both cultivars, which was linked to improved mineral (e.g., K+ and Ca2+) acquisition, and heightened activities of enzymatic antioxidants (e.g., superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, and glutathione S-transferase) and increased levels of non-enzymatic antioxidants (e.g., ascorbic acid, reduced glutathione, phenolics, and flavonoids). LRE also elevated the contents of proline, total free amino acids, total soluble carbohydrates, and water-soluble proteins in both onion bulbs. In general, both cultivars displayed positive responses to LRE pretreatments; however, the Shandaweel cultivar performed better than the Giza 20 cultivar in terms of yield and, to some extent, bulb quality. Collectively, our findings suggest that the application of LRE as biostimulant might be an effective strategy to enhance bulb quality and ultimately the productivity of onion cultivars under field conditions.
Highlights
Innovation of sustainable and environmentally friendly agricultural technologies is the biggest challenge of modern agriculture to ensure a continuous supply of food and nutrition for the burgeoning world population [1]
We examined the effects of licorice (Glycyrrhiza glabra) root extract (LRE) on physiological and biochemical properties, oxidative marker accumulations, antioxidant activities, nutraceutical quality, and growth- and yield-related features of onion cultivars under field conditions
The results of the present study demonstrated that the use of LRE enhanced the contents of photosynthetic pigments in both onion cultivars compared to the corresponding control plants, suggesting that plants supplemented with LRE maintained better photosynthetic capacity (Figure 1A–C)
Summary
Innovation of sustainable and environmentally friendly agricultural technologies is the biggest challenge of modern agriculture to ensure a continuous supply of food and nutrition for the burgeoning world population [1]. The use of biostimulants has recently been identified as a promising natural product application-based approach that offers a flexible, cost-effective, and widely applicable alternative for improving sustainable agricultural productivity while buffering the impacts of climate change [2,3]. Their extensive usage in the agricultural sector has tremendously increased, as indicated by the current global market of around USD 2.0 billion, which is projected to be expanded to USD 3.0 billion by 2021 [4]. In the era of dwindling agricultural lands, it should be a paramount goal of today’s plant scientists and farmers to explore biostimulants as a tonic to boost the yields of commercially valuable crops, including onions (Allium cepa), under field conditions
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