AUTHOR=Zhang Jiahao , Lu Jiemiao , Zhu Yichun , Huang Qinger , Qin Luping , Zhu Bo 

TITLE=Rhizosphere microorganisms of Crocus sativus as antagonists against pathogenic Fusarium oxysporum

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1045147

DOI=10.3389/fpls.2022.1045147

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>Several microorganisms in the plant root system, especially in the rhizosphere, have their own compositions and functions. Corm rot is the most severe disease of <italic>Crocus sativus</italic>, leading to more than 50% mortality in field production.</p></sec><sec><title>Methods</title><p>In this study, metagenomic sequencing was used to analyze microbial composition and function in the rhizosphere of <italic>C. sativus</italic> for possible microbial antagonists against pathogenic <italic>Fusarium oxysporum</italic>.</p></sec><sec><title>Results</title><p>The microbial diversity and composition were different in the <italic>C. sativus</italic> rhizosphere from different habitats. The diversity index (Simpson index) was significantly lower in the <italic>C. sativus</italic> rhizospheric soil from Chongming (Rs_CM) and degenerative <italic>C. sativus</italic> rhizospheric soil from Chongming (RsD_CM) than in others. Linear discriminant analysis effect size results showed that differences among habitats were mainly at the order (Burkholderiales, Micrococcales, and Hypocreales) and genus (<italic>Oidiodendron</italic> and <italic>Marssonina</italic>) levels. Correlation analysis of the relative lesion area of corm rot showed that <italic>Asanoa</italic> was the most negatively correlated bacterial genus (ρ = −0.7934, <italic>p</italic>&lt; 0.001), whereas <italic>Moniliophthora</italic> was the most negatively correlated fungal genus (ρ = −0.7047, <italic>p</italic>&lt; 0.001). The relative lesion area result showed that <italic>C. sativus</italic> from Qiaocheng had the highest resistance, followed by Xiuzhou and Jiande. <italic>C. sativus</italic> groups with high disease resistance had abundant pathogen resistance genes, such as chitinase and β-1,3-glucanase genes, from rhizosphere microorganisms. Further, 13 bacteria and 19 fungi were isolated from <italic>C. sativus</italic> rhizosphere soils, and antagonistic activity against pathogenic <italic>F</italic>. <italic>oxysporum</italic> was observed on potato dextrose agar medium. <italic>In vivo</italic> corm experiments confirmed that <italic>Trichoderma yunnanense</italic> SR38, <italic>Talaromyces</italic> sp. SR55, <italic>Burkholderia gladioli</italic> SR379, and <italic>Enterobacter</italic> sp. SR343 displayed biocontrol activity against corm rot disease, with biocontrol efficiency of 20.26%, 31.37%, 39.22%, and 14.38%, respectively.</p></sec><sec><title>Discussion</title><p>This study uncovers the differences in the microbial community of rhizosphere soil of <italic>C. sativus</italic> with different corm rot disease resistance and reveals the role of four rhizospheric microorganisms in providing the host <italic>C. sativus</italic> with resistance against corm rot. The obtained biocontrol microorganisms can also be used for application research and field management.</p></sec>