Saline‐Water Irrigation Elicits Hormetic Yield Responses in Sweetpotato Across 28 Genotypes Under Field Conditions

ABSTRACT

The use of saline water for irrigation is increasing as the quantity and quality of irrigation water resources are declining. Saline irrigation also provides a means to investigate crop responses to heterogenous salinity, which is a common occurrence in agricultural fields. Crop responses to salinity are dose‐ and genotype dependent, providing opportunities for sustainably managing saline soils and irrigation water. Sweetpotato, a food security crop in regions often affected by salinity and limited water resources, exhibits broad genotypic variation, which provides potential for selecting salt‐adapted genotypes. The effects of saline irrigation on sweetpotato storage root yield were assessed in a split‐plot field trial with 28 genotypes during the dry seasons of 2022 and 2023 in Southern Mozambique. The treatments were freshwater irrigation (control) and saline water irrigation, applied at 37 mM NaCl in 2022 and 75 mM NaCl in 2023, respectively. After 5 months, plants were harvested and assessed for aboveground biomass, yield and yield components, and quality traits. Saline irrigation enhanced mean storage root yield, with an increase of 5 t ha ⁻¹ in 2022 ( p  < 0.05) and 2 t ha ⁻¹ in 2023 ( p  > 0.05). In both years, salinity amplified genotypic variation, with 75 mM NaCl enhancing both positive and negative responses. Genotypic yield ranged from 0.3 to 2.2 times the freshwater yield with hormetic optima being genotype specific. Yield stimulation was associated with larger storage roots and higher harvest indices. Genotypes showing positive yield response also exhibited higher dry matter and sucrose, and lower glucose and fructose concentrations in storage roots grown under salinity. The results demonstrate that saline irrigation can induce hormetic responses in sweetpotato, improving yield in specific genotypes. We hypothesize that adaptive biomass allocation mediated by phloem transport is a potential mechanism underlying salinity hormesis. Strong genotype × salinity interactions at 75 mM NaCl indicate that this treatment may serve as an effective selection environment. Targeted use of saline irrigation with adapted genotypes may support the resilience of sweetpotato production under constrained water resources and seasonal salinity.