Native isolates of Trichoderma as bio-suppressants against sheath blight and stem rot pathogens of rice

Background Species belonging to the genus Trichoderma are considered as one of the most potential biocontrol agents which can be readily collected from soil and found effective against various fungal and bacterial diseases. In rice-growing areas, the major fungal pathogens affecting rice production include Rhizoctonia solani causing sheath blight and Sclerotium oryzae causing stem rot disease of rice. Due to the lack of resistant varieties and detrimental effects of chemicals, biocontrol gives a good opportunity to manage the diseases efficiently in a sustainable manner. Main body Trichoderma spp. from native rice rhizosphere soil were examined for their antagonistic efficiency to supress the two soil-borne rice pathogens, viz., R. solani and S. oryzae. Morphological, biochemical and molecular characterisation of the isolates led to the identification of species as T. asperellum. The isolates of Trichoderma spp. were found to be positive to IAA release and phosphate solubilisation and were screened against R. solani and S. oryzae in vitro and in vivo in pots under glass house conditions. Regression analysis indicated a positive correlation between the amount of chlamydospores produced by T. asperellum and their antagonistic potential against the two pathogens. Exposure to external stimuli, viz., light, injury and nitrogen sources in culture media triggered increased conidiation in Trichoderma isolates. Among the four isolates studied, Trichoderma asperellum IIRRCK1 (TAIK-1) was found to be the most effective in improving plant growth in rice and highly antagonistic against R. solani and S. oryzae. Sorghum grain was found to be the most suitable among different organic substrates studied to provide better growth and viability of TAIK-1 and improved the efficiency of the seed treatment and soil application. External stimuli in the form of near UV blue light, mechanical injury to the colonies and nitrogen source added to the culture media help in faster conidiation of Trichoderma. Conclusion Strain TAIK-1 showed strong competitive and antagonistic activities against fungal soil-borne pathogens, in addition with promoting healthy growth and development of rice plants. This can be a suitable and safe alternative to chemical management in the rice fields for long-term scenario.

Automated summary

Species of Trichoderma genus are effective biocontrol agents against various fungal and bacterial diseases, providing a sustainable alternative to chemical management in rice fields. Trichoderma asperellum strain TAIK-1 showed strong competitive and antagonistic activities against soil-borne pathogens while promoting healthy growth of rice plants. External stimuli like near UV blue light and mechanical injury can enhance conidiation of Trichoderma isolates, improving their efficiency in disease management.