Bacillus valezensis bacterial strain JK-1 as an effective biocontrol strategy against wheat root rot disease

Bipolaris sorokiniana infestation in wheat is highly susceptible to common root rot and leaf black spot diseases, leading to significant yield loss. The detrimental effects of chemical fungicides are evident. However, the development of new biological control methods that meet the requirements of environmentally friendly and sustainable agriculture is still underway. In this study, we screened and identified a bacterial strain, JK-1, which exhibited significant antagonistic effects against B. sorokiniana, as Bacillus velezensis. In the present study, the fermentation filtrate of the antagonist strain JK-1 was prepared and its inhibitory effect on B. sorokiniana was investigated. Treatment with 20% JK-1 culture filtrate (CF) resulted in a reduction of 65.8% in the dry weight of B. sorokiniana mycelium and a decrease of 93.3% in the spore germination rate. Scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) revealed that the culture filtrate (CF) of JK-1 caused significant damage to the integrity of the cell membrane of B. sorokiniana. Additionally, LSCM demonstrated that CF treatment led to increased DNA leakage and the accumulation of reactive oxygen species (ROS) in B. sorokiniana mycelial cells. Moreover, the disruption of the antioxidant defense system of B. sorokiniana by CF was demonstrated through the assessment of key antioxidant enzyme activities. The crude extract of the JK-1 CF was analyzed using liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) and was determined to contain the lipopeptide surfactin. B. velezensis JK-1 exhibited significant control effects in biocontrol experiments involving detached leaves and potting. Furthermore, the JK-1 CF was found to significantly promote the growth of wheat seedlings. These results indicate that B. velezensis JK-1 holds great potential as a strain for controlling wheat root rot and can provide a new approach to wheat management.