Citation: Gallardo, J.; Díaz, M.; Carballo, J.; Garayalde, A.; Echenique, V. Phytolith Content Negatively Affects Forage Quality of Eragrostis curvula (Schrad.) Nees. Agronomy 2023, 13, 924. https:// doi.org/10.3390/agronomy13030924 Academic Editors: Wanjun Zhang and Jingjin Yu Received: 10 February 2023 Revised: 10 March 2023 Accepted: 15 March 2023 Published: 21 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). agronomy Article Phytolith Content Negatively Affects Forage Quality of Eragrostis curvula (Schrad.) Nees Jimena Gallardo 1,2 , Marina Díaz 1,3 , José Carballo 1 , Antonio Garayalde 4 and Viviana Echenique 1,2, * 1 Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS), Universidad Nacional del Sur-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca 8000, Argentina 2 Departamento de Agronomía, Universidad Nacional del Sur (UNS), San Andrés 800, Bahía Blanca 8000, Argentina 3 Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), San Juan 670, Bahía Blanca 8000, Argentina 4 Departamento de Matemática, Universidad Nacional del Sur (UNS), Av. Alem 1253, Bahía Blanca 8000, Argentina * Correspondence: echeniq@cerzos-conicet.gob.ar; Tel.: +54-291-486-1124 Abstract: Phytoliths are intra and extracellular siliceous deposits present in different plant tissues. Si uptake and transport are mediated by Lsi genes and its concentration is associated with forage quality. Our objective was to determine the phytolith content in seven Eragrostis curvula genotypes at the outbreak and re-growth stages to assess its relationship with the forage quality parameters and perform a genome-wide analysis to detect the presence/absence of Lsi genes. The mean values of the phytolith content of dry matter varied between 1.94–2.26% and 2.72–4.71% at the outbreak and re-growth stages, respectively, with highly significant differences among the genotypes and phenological stages. A highly negative correlation was observed in the phytolith content and in vitro dry matter digestibility and crude protein, revealing its importance as a selection parameter in breeding programs. A positive correlation was obtained between the phytolith content and lignin, neutral detergent fiber, and acid detergent fiber. The main morphotypes of the phytoliths included saddle-shaped, bulliform, and acicular cells. Genes Lsi1, Lsi2, Lsi3, and Lsi6, previously reported in silica uptake, were identified and compared with related species, being the gene sequences highly conserved, meaning that its accumulation is probably due to differences in the gene expression or different allelic variants among cultivars. Keywords: phytoliths; weeping lovegrass; dry matter digestibility; Lsi genes 1. Introduction Phytoliths are silica structures that originate from the precipitation and polymerization of silicic acid through a process known as biosilicification, largely distributed throughout the plant kingdom. This process occurs at both intracellular (cytoplasm or vacuole) and intercellular spaces in almost all plant parts (i.e., roots, stems, leaves, fruits and inflores- cences) [1,2]. In soil solution, silica (Si) is present in the form of silicic acid [Si(OH) 4 ], being found in percentages ranging from approximately 10% to close to 100% in some sediments [3]. Its presence is a consequence of the leaching processes of siliceous minerals (for example, quartz and feldspars) as well as the dissolution of the silica biominerals themselves (phy- toliths, diatoms, sponge spicules, among others). Silicic acid is absorbed by plant roots at <9 pH and is transported to different parts of the plant through the vascular system [4]. In most grasses, the uptake of Si is mediated by both an aquaporin-like channel gene Low silicon 1 (Lsi1) and a proton antiporter (Lsi2) gene. The gene Lsi3, together with Lsi2, are involved in the generation of a Si concentration gradient that is used by Lsi6, another aquaporin-like gene, to transport the Si to other organs [5,6]. The content of phytoliths Agronomy 2023, 13, 924. https://doi.org/10.3390/agronomy13030924 https://www.mdpi.com/journal/agronomy