Isolation and Characterization of Root-Associated Bacterial Endophytes and Their Biocontrol Potential against Major Fungal Phytopathogens of Rice (Oryza sativa L.).

Maqsood Ahmed Khaskheli,Dawei Song,Long Chen,Sihui Liu,Sajid Hussain,Guozhong Feng,Lijuan Wu,Guoqing Chen

doi:10.3390/pathogens9030172

Maqsood Ahmed Khaskheli, Dawei Song + Show 6 more

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https://doi.org/10.3390/pathogens9030172

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Journal: Pathogens	Publication Date: Feb 28, 2020
Citations: 31	License type: CC BY 4.0

Affiliation: China National Rice Research Institute

Abstract

Rice (Oryza sativa L.) is a major cereal food crop worldwide, and its growth and yield are affected by several fungal phytopathogens, including Magnaporthe oryzae, Fusarium graminearum, F. moniliforme, and Rhizoctonia solani. In the present study, we have isolated and characterized root-associated bacterial endophytes that have antifungal activities against rice fungal phytopathogens. A total of 122 root-associated bacterial endophytes, belonging to six genera (Bacillus, Fictibacillus, Lysinibacillus, Paenibacillus, Cupriavidus, and Microbacterium) and 22 species were isolated from three rice cultivars. Furthermore, the 16S rRNA sequence-based phylogeny results revealed that Bacillus was the most dominant bacterial genera, and that there were 15 different species among the isolates. Moreover, 71 root-associated endophytes showed antagonistic effects against four major fungal phytopathogens, including M. oryzae, F. graminearum, F. moniliforme, and R. solani. Additionally, the biochemical, physiological, and PCR amplification results of the antibiotic-related genes further supported the endophytes as potential biocontrolling agents against the rice fungal pathogens. Consequently, the findings in this study suggested that the isolated bacterial endophytes might have beneficial roles in rice defense responses, including several bioactive compound syntheses. The outcomes of this study advocate the use of natural endophytes as an alternative strategy towards the rice resistance response.

Highlights

Rice (Oryza sativa L.) is considered to be the most widely used staple food among the cereal crops, as it feeds half of the world’s population [1,2]
In the current investigation, we studied that several types of biochemical and physiological characteristics, including gram reactions (GR), catalase activity (CA), endospore activity (EA), oxidase activity (OA), motility performance (MP), citrate activity (CA), gelatinase production (GP), urease activity (UA), nitrate reduction activity (NRA), Voges–Proskauer performance (VPP), methyl red activity (MRA), starch hydrolyses activity (SHA), glucose activity (GA), mannitol activity (MA), lactose activity (LA), and maltose activity (MA), from the isolated root-associated bacterial endophytes respectively (Table S2)
The main findings of this study revealed that Bacillus bacterial endophyte species were found in rice host plants with an antagonistic response against fungal phytopathogens, and that Bacillus could be suggested as a specific genus to check the biocontrol response against rice fungal pathogens

Summary

Introduction

Rice (Oryza sativa L.) is considered to be the most widely used staple food among the cereal crops, as it feeds half of the world’s population [1,2]. Rice blast, rice seedling blight, rice bakanae, and rice sheath blight caused by Magnaporthe oryzae, Fusarium graminearum, Fusarium moniliforme, and Rhizoctonia solani, respectively, are the common fungal phytopathogenic diseases causing severe crop damage and losses in yield [4,5,6,7,8]. The annual rice grain yield losses due to major fungal diseases were reported to be rice blast (30%), seedling blight, rice bakanae (50%–60%), and sheath blight (40%–50%) in Asian countries [7,9,10]. The focus has been given to the effective biocontrol of these phytopathogens, as the use of excessive fungicides and chemicals can cause pathogen resurgence and other environmental hazards [11,12]

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