A Kappaphycus alvarezii aqueous extract improves yield and kernel quality in barley (Hordeum vulgare L.)

Abstract

The search for sustainable agricultural inputs has increased the interest in biostimulants based on macroalgae. An aqueous extract of Kappaphycus alvarezii , a red seaweed rich in bioactive compounds, has emerged as a promising biostimulant for various crops, in Brazil, but its effects on barley ( Hordeum vulgare L.) remain underexplored. This study investigated the influence of foliar application of different concentrations, i.e., 0, 1, 2, 5, and 10% v/v, of a crude aqueous extract, derived from biomass cultivated in Santa Catarina, southern Brazil. The morphology, yield, and biochemical parameters of leaves and kernels, from treated plants in pots, in a greenhouse were measured. In contrast to the growth-promoting effects reported for other extracts of seaweeds, this Kappaphycus extract did not alter the plant architecture, but selectively enhanced reproductive output, suggesting an optimization of resource allocation towards grain development. It was seen that grain set increased at lower concentrations (1–2%) and the thousand-kernel weight at higher doses (5–10%). Biochemically, this specific extract elevated leaf amino acids by up to 47.4% at the 1% concentration, as compared to control. In addition, treatments selectively enhanced kernel qualities, including starch (+ 19.3%, at 5%), protein (+ 10.3%, at 10%), and amino acids (+ 56.6%, at 1–2%), while maintaining germination viability above 98.5%. PCAs revealed a clear segregation, isolating the control from all treatments, which formed distinct clusters in all parameters. The results demonstrated that the K. alvarezii extract used in this study could be an effective tool for enhancing barley kernel quality, particularly for the malting industry, by optimizing reserve accumulation, without compromising plant morphology and seed germination.

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