Endophytic and saprobic fungi associated with mangoes and potential of Endophytic fungi as biocontrol agents against selected mango pathogens

Abstract

Mango is cultivated in over 100 countries, exists in more than 1,000 varieties worldwide, and is an important agricultural economic industry in several countries. China introduced mango from India in 645 A.D. and has a long history of over 1,300 years of cultivation. Yunnan province is one of China’s main mango planting areas, contributing the annual total economic output of 1.8 billion Chinese Yuan with a mango cultivating area of up to 74,100 Km2 in 2018. The main mango planting regions in Yunnan were distributed in Baoshan, Honghe (Yuanjiang), Lijiang (Huaping), and Pu’er, with Keitt, Guifei, Sannian, Nang Klangwan, and JinHwang as the major varieties. This study carries out endophytic fungi and saprobic fungi associated with mangoes in Yunnan Province (Baoshan and Honghe) and is divided into three parts. In the first part, 34 endophytic fungi strains were isolated from mango health leaves. Based on phylogenetic analyses of ITS locus and cultures morphological observation in potato dextrose agar (PDA), those isolates belong to three classes and 12 different orders (Amphisphaeriales, Botryosphaeriales, Calosphaeriales, Capnodiales, Diaporthales, Glomerellales, Hypocreales, Mycosphaerellales, Pezizles, Pleosporales, Sordariales and Xylariales) and the family Chaetomiaceae (Chaetomium spp.) has the highest diversity. In the second part, the 34 fungal endophytic strains from the first part were used for screening antagonistic properties in the vitro assay. All endophytic fungi were tested with two fungi (Penicillium digitatum CGMCC 3.15410 and Botrytis cinerea CGMCC 3.3790) and two bacterial pathogens (Pseudomonas syringae CGMCC 1.3333 and Erwinia amylovora CGMCC 1.7276). The results showed Chaetomium strains. (KUNCC22-10749, KUNCC22-10750 and KUNCC22-10752) exhibit antagonistic properties (>=50%) against two bacterial pathogens. While Alternaria (KUNCC22-10760), Chaetomium (KUNCC22-10749), Daldinia (KUNCC22-10744) and Rosellinia (KUNCC22-10751) exhibited antagonistic properties against two fungal pathogens. In the third part, 20 saprobic fungal species from decaying woody substrates of mango were isolated and identified. The morphological examination and phylogenetic analyses provide, evidence for known and novelties taxa, including two new genera Mangifericomes and Mangiferivora and eight novel species Cyphellophora hongheensis, Diaporthe hongheensis, Hypoxylon hongheensis, Mangifericomes hongheensis, Mangiferivora hongheensis, Neomassaria hongheensis, Paramonodictys hongheensis, Paramonodictys yunnanensis. In addition, six new host and country records (Aplosporella artocarpi, Byssosphaeria siamensis, Crassiparies quadrisporus, Paradictyoarthrinium diffractum, Pleurostoma ootheca, Vaginatispora amygdali), the four new host records (Eutypella citricola, Hypomontagnella monticulosa, Phaeoseptum mali and Torula fici). Descriptions and illustrations of the above taxa are provided and their systematic placement is discussed. This study increases the knowledge of the diversity of microfungi associated with mango, both endophytic and saprobic fungi. All the fungi related to this study were confirmed for phylogenetic relationship based on morphology and DNA sequences. In addition, endophytic fungi from mango leaves showed remarkable growth inhibition against the tested pathogenic bacteria and fungi. This revealed that the endophytic fungi from mango are potentially as alternative biocontrol agents against mango diseases.