Paenibacillus polymyxa 29-Y2: A Promising Endophytic Biocontrol Agent Against Wheat Common Bunt Caused by Tilletia foetida

Wheat common bunt, caused by Tilletia foetida Liro, is a devastating disease in wheat production. In this study, the antagonistic endophytic bacteria 29-Y2 were screened based on the germination rate of teliospore and the control effect of wheat common bunt. During primary screening, 29-Y2 had the best performance, with a 96.73% inhibition on TFL spore germination. In the deep screening, the control effect of 29-Y2 on wheat common bunt was 66.12% in pots. Based on morphological, physiological, and biochemical characteristics and molecular biological identification, the antagonist 29-Y2 was identified as Paenibacillus polymyxa. The antagonist 29-Y2 promoted the germination rate of wheat seeds and the growth of wheat seedlings at a solution dilution of 10−5 cfu/mL. In different field trials, the antagonists 29-Y2 both had better control efficiencies of 62.31% and 67.62% for wheat common bunt. In order to further promote the inhibition activities of 29-Y2, the optimal culture condition was 11.1 g/L of glucose, 20 g/L of yeast extract powder, 3.8 g/L of soybean pepyone and 10 g/L of NaCl based on the response surface methodology; the liquid loading volume was 15 mL, of which the inoculant amount accounted for 2%, the pH was 6.8, the temperature was 30 °C and the rotation speed was 186 r/min for 26 h. When the fermentation broth obtained under these cultivation conditions was diluted 10,000 times, the inhibition rate of TFL teliospore germination could reach 80.32%. The fermentation broth control effect in pots improved from 57.77% to 84.17%. It was a promising endophytic bacterium for the prevention and control of wheat common bunt.