Improved Salinity Resilience in Black Bean by Seed Elicitation Using Organic Compounds

The adaptive responses of plants to abiotic stress include stimulation of secondary metabolites and endogenous antioxidant enzymes through up-regulation of the pentose phosphate pathway (PPP). Therefore improving abiotic stress resilience in food crops through upregulation of critical redox-linked anabolic PPP and enhancement of phenolic-linked antioxidant enzyme responses has merit. This study evaluated the effects of seed elicitor treatments (chitosan oligosaccharide [COS] Kong Poong Bio, Jeju, Korea, and marine hydrolysate [GroPro], Icelandic Bioenhancer, Harrison, NY) to improve salinity stress resilience through up-regulation of PPP in black bean (Phaseolus vulgaris L.) cultivars. Eclipse and Zenith cultivars were subjected to elicitor treatments (1%) and then 1 wk after germination were transplanted into three soil salinity treatments (no salt, 2-3, and 5-6 dS m(-1)) in greenhouse. Elicitation resulted in enhanced survival at medium salt stress (2-3 dS m(-1)), however none survived more than 55 to 60 d post germination under high salt stress (5-6 dS m(-1)). Stimulation of phenolic biosynthesis through up-regulation of PPP was confirmed in Eclipse, while Zenith exhibited higher reliance by stimulation of endogenous antioxidant enzyme responses to counter salinity stress. GroPro induced elicitation improved total soluble phenolic content (60 d) and higher glucose-6-phosphate dehydrogenase (G6PDH) activity (45 d) in Eclipse. In Zenith, GroPro stimulated antioxidant enzyme responses (superoxide dismutase [SOD] and guaiacol peroxidase [GPX]) during later growth stages, while COS elicitation improved antioxidant response in early stages. Therefore seed elicitation can be a selective strategy to improve salinity stress resilience in black bean.