plants Article In Vitro Evaluation of the Inhibitory Activity of Different Selenium Chemical Forms on the Growth of a Fusarium proliferatum Strain Isolated from Rice Seedlings Elisabetta Troni 1 , Giovanni Beccari 1, * , Roberto D’Amato 1, * , Francesco Tini 1 , David Baldo 2 , Maria Teresa Senatore 2 , Gian Maria Beone 3 , Maria Chiara Fontanella 3 , Antonio Prodi 2 , Daniela Businelli 1 and Lorenzo Covarelli 1   Citation: Troni, E.; Beccari, G.; D’Amato, R.; Tini, F.; Baldo, D.; Senatore, M.T.; Beone, G.M.; Fontanella, M.C.; Prodi, A.; Businelli, D.; et al. In Vitro Evaluation of the Inhibitory Activity of Different Selenium Chemical Forms on the Growth of a Fusarium proliferatum Strain Isolated from Rice Seedlings. Plants 2021, 10, 1725. https:// doi.org/10.3390/plants10081725 Academic Editors: Dragana Šunjka and Špela Mechora Received: 2 August 2021 Accepted: 17 August 2021 Published: 20 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 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/). 1 Department of Agricultural, Food and Environmental Sciences, University of Perugia, 06121 Perugia, Italy; elisabetta8891@gmail.com (E.T.); francesco.tini@collaboratori.unipg.it (F.T.); daniela.businelli@unipg.it (D.B.); lorenzo.covarelli@unipg.it (L.C.) 2 Department of Agricultural and Food Sciences, Alma Mater Studiorum University of Bologna, 40127 Bologna, Italy; david.baldo@unibo.it (D.B.); mariateresa.senatore@unibo.it (M.T.S.); antonio.prodi@unibo.it (A.P.) 3 Department for Sustainable Food Process, Catholic University of the Sacred Heart of Piacenza, 29122 Piacenza, Italy; gian.beone@unicatt.it (G.M.B.); mariachiara.fontanella@unicatt.it (M.C.F.) * Correspondence: giovanni.beccari@unipg.it (G.B.); roberto.damato@unipg.it (R.D.) Abstract: In this study, the in vitro effects of different Se concentrations (5, 10, 15, 20, and 100 mg kg −1 ) from different Se forms (sodium selenite, sodium selenate, selenomethionine, and selenocystine) on the development of a Fusarium proliferatum strain isolated from rice were investigated. A concentration-dependent effect was detected. Se reduced fungal growth starting from 10 mg kg −1 and increasing the concentration (15, 20, and 100 mg kg −1 ) enhanced the inhibitory effect. Se bioac- tivity was also chemical form dependent. Selenocystine was found to be the most effective at the lowest concentration (5 mg kg −1 ). Complete growth inhibition was observed at 20 mg kg −1 of Se from selenite, selenomethionine, and selenocystine. Se speciation analysis revealed that fungus was able to change the Se speciation when the lowest Se concentration was applied. Scanning Electron Microscopy showed an alteration of the fungal morphology induced by Se. Considering that the inorganic forms have a higher solubility in water and are cheaper than organic forms, 20 mg kg −1 of Se from selenite can be suggested as the best combination suitable to inhibit F. proliferatum strain. The addition of low concentrations of Se from selenite to conventional fungicides may be a promising alternative approach for the control of Fusarium species. Keywords: fungi; Fusarium; selenium; micronutrient; inhibition; bioactivity 1. Introduction Selenium (Se) is an essential micronutrient for humans and animals, and is involved in numerous biological processes, such as cellular response to oxidative stress, cellular differentiation, redox signaling, and protein folding [1–3]. More than 25 Se-containing proteins have been identified in mammals, having a role in the regulation of redox processes. Among Se proteins, Se is a crucial component of glutathione peroxidase, whose main biological role is to protect against oxidative damage by reducing free hydrogen peroxide to water and lipid hydroperoxides to their corresponding alcohols [4]. In addition to humans and animals, Se is also beneficial to plants when applied at low concentrations [5–8]. For example, Se contributes to the control of water status [9], prevents oxidative stress, delays senescence, and promotes growth [10]. Due to this experimental evidence, numerous studies have investigated Se-biofortification strategies for providing plant protection against abiotic stresses and, at the same time, when possible, beneficial food for human health [11–13]. As demonstrated for many other nutrients, Se Plants 2021, 10, 1725. https://doi.org/10.3390/plants10081725 https://www.mdpi.com/journal/plants