Effects of Trichoderma harzianum and Arthrobacter ureafaciens on control of Fusarium crown rot and microbial communities in wheat root-zone soil

Abstract Biocontrol by inoculation with beneficial microbes is a proven strategy for reducing the negative effect of soil-borne pathogens. The effects of Trichoderma harzianum LTR-2 and Arthrobacter ureafaciens DnL1-1 on reducing Fusarium crown rot (FCR) disease and influencing microbial community structure in wheat root-zone were evaluated by a plot experiment. The experimental design consisted of four treatments: (1) control, (2) Fusarium pseudograminearum Fp (FP), (3) F. pseudograminearum + LTR-2 (LFP), and (4) F. pseudograminearum + LTR-2 + DnL1-1 (HFP). The results showed that wheat seeds coated with LTR-2 spore suspension and combination of LTR-2 and DnL1-1 had relative control efficacies of 50.77% and 67.73% on FCR disease, and increased wheat yield by 58.32% and 64.19%, respectively. Illumina MiSeq sequencing revealed that bacterial and fungal abundance and diversity were significantly higher ( P < 0.05) in both treatment groups (HFP and LFP) than in FP and control groups. Principal coordinates analyses revealed that fungal and bacterial communities were distinctly separated among the treatment and control groups. Fungal community composition analysis demonstrated that the relative abundance of phytopathogenic fungi Alternaria , Fusarium , and Cladosporium decreased and that of beneficial fungi Mortierella and Gamsia was more enriched in HFP and LFP than in FP group. Bacterial community composition analysis revealed that the beneficial microbes, such as Bacillus and Streptomyces were more abundant in HFP and LFP than in FP group. LEfSe analysis indicated that the key different genera, e.g. Tetracladium (fungus), Sphingomonas and Ramlibacter (bacteria), which were significantly negatively correlated with TP in HFP treatment. It was concluded that application of LTR-2 and DnL1-1 may recruit a variety of phosphate-solubilizing microbes to promote wheat growth. Overall, these results confirm that the relative abundance of phytopathogenic fungi decreased significantly following application of LTR-2 alone and combined with DnL1-1 and beneficial microbes accumulated more easily in the wheat root-zone compared with that in FP and control groups.