Characterisation of endophytic Bacillus thuringiensis strains isolated from wheat plants as biocontrol agents against wheat flag smut

Abstract

To explore effective and ecofriendly means of controlling wheat flag smut (WFS) using biocontrol agents, three endophytic strains (58-2-1, 37-1 and YC-1) of Bacillus sp. were isolated from winter wheat plants in China and identified as Bacillus thuringiensis based on their 16S rDNA sequences as well as phenotypic characteristics. Four morphological (leaf length, root length, dry weight and tiller numbers) and one physiological [root vigour (RV)] parameters of wheat plants treated by strains 58-2-1 and 37-1 were significantly enhanced compared to the control. The soluble sugar contents in the roots of wheat samples treated by the two strains were significantly lower than the control. The resistance of wheat varieties to WFS was investigated by inoculation tests. Of the 12 wheat varieties tested, 6 (Yunhan-618, Bainongaikang-58, Kaimai-20, Zhengmai-9023, 04-zhong-36 and Yanzhan-4110) were identified as WFS-highly resistant (HR), 3 (Pumai-9, Jinboshi-1 and Yunong-202) WFS-moderately resistant (MR), 1 (Yubao-1) WFS-susceptible (S) and 2 (Yumai-012 and Yunong-416) WFS-highly susceptible (HS) varieties. The Urocystis tritici-induced yield loss on the S/HS varieties was significantly higher than that on the HR/MR ones. The strains 58-2-1 and 37-1 had control efficacies of 6.7–100% (av.54.8%) and 33.3–100% (av. 66.5%) on 9 and 7 out of 12 varieties, respectively. The strains 58-2-1 and 37-1 had enhanced yields of 10.2–54.9% (av. 32.9%) and 2.8–43.4% (av. 24.8%) on 10 and 8 out of 12 varieties, respectively. This is the first report on endophytic B. thuringiensis strains isolated from wheat plants with the abilities to suppress WFS and to enhance yields on multiple wheat varieties.