Seed Priming with Devosia sp. Cell-Free Supernatant (CFS) and Citrus Bioflavonoids Enhance Canola and Soybean Seed Germination

Abstract

Climate change, environmental pollution and associated abiotic stresses are beginning to meaningfully affect agricultural production worldwide. Salt stress is, however, one of the most important threats that significantly impairs plant growth and development. Plants in their early growth stages such as seed germination, seed emergence and early seedling growth are very sensitive to salt stress. Among the range of sustainable techniques adopted to improve seed germination and early plant growth is seed priming; however, with the use of ecofriendly substances, this is one of the most effective and economically viable techniques to improve seed tolerance against such environmental stresses. For instance, priming with appropriate non-synthetic compounds including microbial biostimulants are prominent ways to sustainably address these challenges. Therefore, in this research, by using the “priming technique”, two biostimulants were tested for their potential as sustainable approaches to improve canola and soybean seed germination under salt stress and optimal growth conditions. Canola and soybean seeds were primed with flavonoids extracted from citrus fruits (flavopriming) and cell-free supernatant (CFS; produced by a novel strain of Devosia sp.—SL43), alone and in combination, and exposed to low–higher levels of salt stress and ideal growth conditions. Both biostimulants showed promising effects by significantly improving seed germination of soybean and canola under both ideal and stressful conditions. However, increases in seed germination were greater under salinity stress as flavonoids and CFS with stress amelioration effects showed substantial and statistically significant improvements in seed germination under varying levels of salt stress. In addition, combinations (mixtures) of both biostimulants were tested to determine if their effects might be more additive or multiplicative than the individual applications. However, results suggested incompatibility of both biostimulants as none of the combinations showed better results than that of the individual applications of either flavonoids or CFS. Conceivably, the use of flavonoids and this novel Devosia sp. CFS could be significant plant growth enhancers, perhaps much better than the few other biostimulants and bacterial-based compounds currently in use.

Flavonoids and Devosia sp SL43 cell-free supernatant increase early plant growth under salt stress and optimal growth conditions

“…In addition, increased potential has been observed for this bacteriocin and a bacterium-produced nod factor (LCO) in promoting soybean growth under stressful conditions ( Gautam et al., 2016 ). In this part of the research, the CFS, after successful trials on seed germination of soybean and canola ( Shah et al., 2022 ), was applied as foliar spray with the thinking that it would increase the growth of both crops under salt stress and optimal growth conditions. Arguably, soybean growth was unaffected by CFS under optimal growth conditions, however, this is not overly surprising as many of the bacteria-to-plant signal compounds show little or no effects in the absence of stress, and large effects in the presence of stress ( Subramanian et al., 2016b ), particularly at lower concentrations ( Gautam et al., 2016 ).…”

“…strain (SL43), isolated from Amphicarpaea bracteate plants growing wild along the shore of Lac St. Louis, Sainte-Anne-de-Bellevue, Quebec, Canada. Three dilutions were prepared from the extract material, and selected for foliar spray doses on canola and soybean based on our seed germination experiments with the extracted material ( Shah et al., 2022 ); minimum (1:100), intermediate (1:500) and maximum (1:1000) dilutions. ( Table 2 ).…”

“…Although their application is gradually increasing, and growers are developing more interest in sustainability, there is still a gap to be filled. In this study, two biostimulants: CFS (SL43) and flavonoids; after successful trials as seed treatments ( Shah et al., 2022 ), were evaluated for their growth stimulatory effects as foliar sprays. The purpose of this study was to determine whether or not these products can be used on crop foliage, and how effective they are in improving the growth and resistance of canola and soybean under both optimal and salt stress growth conditions.…”

Lactobacillus helveticus EL2006H cell-free supernatant enhances growth variables in Zea mays (maize), Glycine max L. Merill (soybean) and Solanum tuberosum (potato) exposed to NaCl stress

“…The association between PGPM and their host plants can enhance the latter’s growth and development, through mechanisms such as biostimulation, mitigation of abiotic stress effects, bioremediation and biocontrol ( Glick, 2012 ; Ahemad and Kibret, 2014 ; Backer et al, 2018 ; Naamala and Smith, 2020 ), in a sustainable and environmentally friendly manner ( Naamala and Smith, 2021a , b ). PGPM and their derived compounds can be utilised in singular or consortium forms, results varying in such a way that some strains may be more effective when applied as single cells while others, in a consortium ( Giassi et al, 2016 ; Subramanian et al, 2016a , b ; Shah et al, 2022 ). Lactobacillus helveticus is a gram positive facultative anaerobic lactic acid bacterium (LAB) that is mostly known for its role in the food processing industry.…”

“…Recent studies have focused on the possibility that such metabolite rich media, also known as cell-free supernatant (CFS) can enhance plant growth without the presence of microbial cells. Experimentation with CFSs has previously yielded interesting results, showing that such CFSs can enhance the growth of different crop species, such as corn, soybean, canola and tomato, at germination and seedling stages ( Msimbira et al, 2022 ; Naamala et al, 2022 , Shah et al, 2022 ). Earlier studies went further and extracted bioactive compounds from the CFS, resulting in the discovery of compounds such as lipo-chitooligosaccharide (LCO) from Bradyrhizobium japonicum CFS and thuricin17 from Bacillus thuringiensis NEB17 CFS ( Prithiviraj et al, 2003 ; Gray et al, 2006a , b ; Lee et al, 2009 ), which are already on the market as plant growth promoting biostimulants.…”