agriculture Article Mycorrhizal Fungal Diversity and Its Relationship with Soil Properties in Camellia oleifera Rui-Cheng Liu 1 , Zhi-Yan Xiao 2 , Abeer Hashem 3,4 , Elsayed Fathi Abd_Allah 5 and Qiang-Sheng Wu 1, *   Citation: Liu, R.-C.; Xiao, Z.-Y.; Hashem, A.; Abd_Allah, E.F.; Wu, Q.-S. Mycorrhizal Fungal Diversity and Its Relationship with Soil Properties in Camellia oleifera. Agriculture 2021, 11, 470. https://doi. org/10.3390/agriculture11060470 Academic Editors: Isabelle Trinsoutrot-Gattin and Babacar Thioye Received: 16 April 2021 Accepted: 20 May 2021 Published: 21 May 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 College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China; liunian10111226@163.com 2 Wuhan Forestry Workstation, Wuhan 430023, China; xzhyan@163.com 3 Botany and Microbiology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia; habeer@ksu.edu.sa 4 Mycology and Plant Disease Survey Department, Plant Pathology Research Institute, ARC, Giza 12511, Egypt 5 Plant Production Department, Faculty of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Saudi Arabia; eabdallah@ksu.edu.sa * Correspondence: wuqiangsheng@yangtzeu.edu.cn or wuqiangsh@163.com Abstract: Arbuscular mycorrhizal fungi (AMF) are well known for their important physiological implications on diversified host plants, while the information on AMF diversity and its relationship with soil properties of Camellia oleifera is yet not fully understood. In the proposed study, high- throughput sequencing of small subunit ribosomal RNA was performed to analyze the AMF diversity of the rhizosphere and endosphere of 20-year-old C. oleifera Xianglin in the field at Wuhan (China) and their relationship with soil physico-chemical properties. As high as 30.73–41.68% of the roots of C. oleifera were colonized by indigenous AMF with a spore density of 66–111 spores/10 g soil. The surface soil (0–20 cm) showed significantly higher root fungal colonization, spore density, soil hyphal length, and easily extractable glomalin-related soil protein content than the sub-surface soil (20–40 cm). Soil pH value, available K, and NO 3 − -N content affected the root and soil mycorrhizal development, whilst soil pH proved to be the most influential soil property governing their variability. A total of 467 OTUs associated with AMF were detected from the endosphere and rhizosphere, representing 10 genera and 138 species, of which 295 OTUs and 9 genera were jointly observed. The genus Glomus displayed maximum relative abundance (>86%) in both endosphere and rhizosphere. Scutellospora was detected in the endosphere, but absent in the rhizosphere. The endosphere recorded a relatively higher number of OTUs and alpha diversity indices (Shannon, Simpson, and PD index) of AMF than rhizosphere. Our study, hence, revealed that C. oleifera in fields was mainly colonized by Glomus, coupled with comparatively greater AMF diversity in the endosphere than in the rhizosphere, governed predominantly by soil pH, NO 3 − -N content, and available K content. Keywords: Glomus; high-throughput sequencing; mycorrhiza; OTU; oil plant 1. Introduction Camellia oleifera is an evergreen woody edible oil plant, widely distributed in the subtropical areas of southern China, and less frequently in northern Southeast Asia [1]. Seeds of C. oleifera are extracted for oils (tea oil), as well known for fragrance, nutritive value, and long storage. Tea oil is a high-quality edible oil that protects the liver from oxidative damage caused by CCl 4 [2]. C. oleifera is also used in the industry as a pesticide as well as the fertilizer, with the ability to improve water storage capacity of farmland and pests’ suppressive ability in rice fields [3,4]. Pharmacological studies showed that seeds of C. oleifera contained various bioactive substances and are traditionally used as folk medicine against bacterial infections, stomach pains, and burns [5]. The demand for C. oleifera has increased greatly in recent years, encouraging the planting area increasing by leaps and bounds. However, the seed yield of C. oleifera is not high, reported as 21–25 t/hm 2 [6]. Agriculture 2021, 11, 470. https://doi.org/10.3390/agriculture11060470 https://www.mdpi.com/journal/agriculture