Management of bakanae disease of rice using biocontrol agents and insights into their biocontrol mechanisms.

Bakanae disease is an emerging problem for the Basmati rice cultivation in India. Forty-seven endophytes isolated earlier along with three Talaromyces flavus isolates evaluated against Fusaium fujikuroi [Nirenberg] bakanae pathogen [isolate F250] through dual culture and enzymatic assays. Out of 50 isolates, 6 isolates namely, Tf1, Tf2, Tf3, Fusarium equiseti, Fusarium sp. and Trichoderma sp. produced good inhibitory results under in vitro conditions and were proceeded with in planta studies and conducted microscopic studies and real-time PCR assays. Microscopic studies revealed that the defense response system of plants was activated to a longer extent in bioagent treatments, since the number of live nuclei (DAPI staining) and green stained live plant cells (FDA staining) were higher as seen in treated plants when compared to pathogen-inoculated and uninoculated control when observed under confocal laser scanning microscopy. The analysis of cell cycle-related genes expressed during the ROS activity showed increased expression of the cell cycle-related genes involved. The selected isolates were also tested under glasshouse for disease inhibition studies. F. equiseti, Fusarium sp. and Trichoderma sp. gave a disease inhibition of, 87%, 66% and 94%, respectively. Tf2 and Tf1 isolate dominantly inhibited the disease with 95% whereas Tf3 also inhibited successfully with 70%. Through the results of our study, we can deduce that the T. flavus (Tf1, Tf2, Tf3) isolates and the endophytes F. equiseti, Fusarium sp. and Trichoderma sp. may represent an important biocontrol agent to control the bakanae disease of rice and also implicated that could further be befitting to capitalize them for field evaluations.