Eco-friendly management of false smut disease of rice incited by <i>Ustilaginoidea virens</i> through the application of <i>Trichoderma</i> spp

Abstract

False smut disease of rice incited by Ustilaginoidea virens is an organ-specific pathogen that causes chalkiness of grain which leads to a reduction in 1000 grain test weight and yield. The dual culture assay results revealed that each Trichoderma isolates suppress the mean mycelial growth of U. virens under in-vitro conditions. Among the nine different Trichoderma isolates, 3 isolates were selected as effective isolates viz., TKM1, TKT9 and TTN5. Among these three effective isolates, maximum mycelial growth inhibition was recorded in the isolate TKM1 with 80.18 percentage reduction over control. The SEM photographs revealed that the hyphal round off in U. virens which is mainly due to the production of volatiles through direct antagonistic activity and competition through indirect antagonistic activity in which conidial adherence of T. harzianum over the surface of the mycelial mat of U. virens was observed. In 2020, the field experiment results revealed that the minimum disease severity was recorded when the Trichoderma isolate TKM1 was sprayed during booting stage with 4.61%, 50% PE stage with 17.91% and 100% PE with 21.86%. In 2021 the disease severity varied from 9.21% to 69.59%. The lowest disease severity was recorded in the plots sprayed with propiconazole fungicide with 9.21%. However, the disease severity recorded in fungicide treated plots were statistically on par with the Trichoderma isolate TKM1 treated plots at 50% PE spray with 10.60%. The disease severity recorded in the plots sprayed with TKM1 showed non-significant relationship with the fungicide treated plots which clearly revealed that the control efficacy of both TKM1 and Propiconazole treated plots were similar with each other. Among the Trichoderma treated plots the yield gain varied from 10.01% to17.20%. The yield gain was found to be 18.35% in fungicide treated plots. The yield and yield gain obtained by the effective isolate TKM1 (yield = 6405 kg/ha and yield gain = 17.20%) was statistically on par with propiconazole treated plots and significantly showed better yield and yield gain than the control plots. In 2021 among the Trichoderma treated plots the yield gain varied from 4.10% to 10.16%. The maximum yield gain was recorded in the fungicide treated plots (12.00%).