biology Review Trends in Nanotechnology and Its Potentialities to Control Plant Pathogenic Fungi: A Review Abdulaziz Bashir Kutawa 1,2,* , Khairulmazmi Ahmad 1,3,* , Asgar Ali 4,* , Mohd Zobir Hussein 5 , Mohd Aswad Abdul Wahab 1, Abdullahi Adamu 1,6 , Abubakar A. Ismaila 1,7, Mahesh Tiran Gunasena 1,8, Muhammad Ziaur Rahman 1,9 and Md Imam Hossain 1 1 Department of Plant Protection, Faculty of Agriculture, Universiti Putra Malaysia, Serdang 43400, Malaysia; [email protected] (M.A.A.W.); [email protected] (A.A.); [email protected] (A.A.I.); [email protected] (M.T.G.); [email protected] (M.Z.R.); [email protected] (M.I.H.) 2 Department of Biological Sciences, Faculty of Life Science, Federal University Dutsin-Ma, Dutsin-ma P.M.B 5001, Nigeria 3 Sustainable Agronomy and Crop Protection, Institute of Plantation Studies (IKP), Universiti Putra Malaysia, Serdang 43400, Malaysia 4 Centre of Excellence for Postharvest Biotechnology (CEPB), School of Biosciences, University of Nottingham Malaysia, Jalan Broga, Semenyih 43500, Malaysia 5 Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, Serdang 43400, Malaysia; [email protected] 6 Department of Biological Sciences, Faculty of Science, Sokoto State University, Birnin Kebbi Road, Citation: Kutawa, A.B.; Ahmad, K.; Sokoto P.M.B 2134, Nigeria 7 Ali, A.; Hussein, M.Z.; Abdul Wahab, Department of Integrated Science, School of Secondary Education (Science), Federal College of M.A.; Adamu, A.; Ismaila, A.A.; Education (Technical), Bichi P.M.B 3473, Nigeria 8 Gunasena, M.T.; Rahman, M.Z.; Grain Legume and Oil Crop Research and Development Centre, Angunakolapelessa 82220, Sri Lanka 9 Plant Pathology Division, Regional Agricultural Research Station (RARS), Bangladesh Agricultural Research Hossain, M.I. Trends in Institute (BARI), Barishal 8211, Bangladesh Nanotechnology and Its Potentialities * Correspondence: [email protected] (A.B.K.); [email protected] (K.A.); to Control Plant Pathogenic Fungi: [email protected] (A.A.) A Review. Biology 2021, 10, 881. https://doi.org/10.3390/ Simple Summary: Fungal pathogens were reported to cause about 70–80% losses in yield. Nanotech- biology10090881 nology can be a panacea to this problem by reducing the negative effect of the fungicides, enhancing the solubility of low water-soluble fungicides, and reducing their toxic effect in a sustainable and eco- Academic Editors: Maria Doroteia Campos and Maria do friendly manner. This review focuses on the description, properties, and synthesis of nanoparticles, Rosário Félix their utilization for plant pathogenic fungal disease control (either in the form of nanoparticles alone, or in the form of a nanocarrier for several fungicides), nano-formulations of agro-nanofungicides, Received: 5 July 2021 Zataria multiflora, and ginger essential oils to control plant pathogenic fungi, as well as the biosafety Accepted: 28 July 2021 and limitations of the nanoparticles applications. Published: 8 September 2021 Abstract: Approximately 15–18% of crops losses occur as a result of animal pests, while weeds and Publisher’s Note: MDPI stays neutral microbial diseases cause 34 and 16% losses, respectively. Fungal pathogens cause about 70–80% losses with regard to jurisdictional claims in in yield. The present strategies for plant disease control depend transcendently on agrochemicals that published maps and institutional affil- cause negative effects on the environment and humans. Nanotechnology can help by reducing the iations. negative impact of the fungicides, such as enhancing the solubility of low water-soluble fungicides, increasing the shelf-life, and reducing toxicity, in a sustainable and eco-friendly manner. Despite many advantages of the utilization of nanoparticles, very few nanoparticle-based products have so far been produced in commercial quantities for agricultural purposes. The shortage of commercial Copyright: © 2021 by the authors. uses may be associated with many factors, for example, a lack of pest crop host systems usage and Licensee MDPI, Basel, Switzerland. the insufficient number of field trials. In some areas, nanotechnology has been advanced, and the best This article is an open access article way to be in touch with the advances in nanotechnology in agriculture is to understand the major distributed under the terms and aspect of the research and to address the scientific gaps in order to facilitate the development which conditions of the Creative Commons Attribution (CC BY) license (https:// can provide a rationale of different nanoproducts in commercial quantity. In this review, we, therefore, creativecommons.org/licenses/by/ described the properties and synthesis of nanoparticles, their utilization for plant pathogenic fungal 4.0/). disease control (either in the form of (a) nanoparticles alone, that act as a protectant or (b) in the Biology 2021, 10, 881. https://doi.org/10.3390/biology10090881 https://www.mdpi.com/journal/biology Biology 2021, 10, 881 2 of 26 form of a nanocarrier for different fungicides), nano-formulations of agro-nanofungicides, Zataria multiflora, and ginger essential oils to control plant pathogenic fungi, as well as the biosafety and limitations of the nanoparticles applications. Keywords: biosafety; disease control; essential oils; fungi; nanocarrier; nanoparticle; nanopesti- cides; nanotechnology 1. Introduction Agriculture plays a vital role by providing nourishment and serving as a source of income for many countries. It is the major source of livelihood for people in rural areas; about 86% of the rural people depend on agricultural cultivation [1]. Approximately 15–18% of crops losses occur as a result of animal pests, while weeds and microbial diseases cause 34 and 16% losses, respectively. Fungal pathogens cause about 70–80% losses in yield [1]. Approximately, there are 1.5 million species that are classified under the kingdom ‘fungi’ and these fungal pathogens are mostly parasitic and saprophytic in nature, causing different diseases in agricultural crops. Fungal pathogens may cause serious decreases in the yield of different crops worldwide each year [2,3]. Presently, disease control depends on the utilization of agrochemicals, for example, fungicides. Regardless of numerous favorable advantages, such as fast action, reliability, and high availability, fungicides can cause negative impacts on the non-target living organisms because of their toxicity and their systemic mode of action by disrupting the metabolite levels in the biosynthetic pathway of aromatic amino acids within the soil microorganisms, the development of resistance, and resurgence in the population of pests and environment [4,5]. Moreover, it is assessed and estimated that about 80–90% of sprayed fungicides are lost to the environment after or during their applications [5,6]. Accordingly, there is an urgent need to procure high- performance fungicides which are cost-effective and cause less negative impacts to the environment. Nanotechnology has prompted the advancement of novel ideas and agriproducts having tremendous potential to address the aforementioned issues. Nanotechnology has progressed in areas of pharmacology and medicine, yet has not developed nearly as much in agricultural uses [7]. The utilization of nanotechnology in the agricultural sector is presently being investigated in the delivery of plant chemical, water, and seed control, nanobarcoding, transfer of genes, controlled release of agrochemicals, and nanosensors [8]. Many researchers have designed nanoparticles pertaining to different qualities, such as pore size, surface properties, and shape, in such a way that they would be utilized as protectants or for exact delivery through encapsulation, and adsorption of an active ingredient [8]. There is a possibility for nanotechnology in agriculture to create and give another age of fungicides and different active ingredients for fungal disease control in plants, as presented in Figure1. The application of nanoparticles for plants protection could be achieved using two types of mechanisms: (a) as individual nanoparticles giving protection in plants; or (b) nanoparticles as fungicides transporters of different active ingredients, for example, fertil- izers, which could be applied by soaking/drenching or by spraying onto the foliar tissue, roots, or seeds. Nanoparticles serve as a carrier and may give numerous advantages such as (i) enhanced solubility of low water-soluble fungicides; (ii) enhanced shelf-life; (iii) improved site-specific uptake in the targeted microbe; and (iv) reduced toxicity [9]. Other advantage of the nanocarrier system is the increment for the efficacy of the stability and activity of the nanofungicides under different ecological factors, essentially reducing the number as well as the quantity of applications, which accordingly diminishes harmfulness and decreases their expenses or cost. BiologyBiology 20212021,, 1010,, 881x FOR PEER REVIEW 3 of 26 Figure 1. (a) Different nanomaterialsnanomaterials as protectants usedused inin plantplant protection.protection. (b) Nanomaterials as transporters forfor several active ingredientsingredients suchsuch asas fungicides.fungicides. (c) NanomaterialsNanomaterials targetingtargeting differentdifferent fungalfungal pathogens.pathogens. (d) TheThe potentialitiespotentialities ofof nanomaterials to provideprovide protectionprotection toto thethe plant.plant. TheNanotechnology application of has nanoparticles played an important for plants role