Abstract
BackgroundSpecies 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 bodyTrichoderma 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.ConclusionStrain 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.
Highlights
ConclusionStrain TAIK-1 showed strong competitive and antagonistic activities against fungal soil-borne pathogens, in addition with promoting healthy growth and development of rice plants
Materials and methods Bioagents and pathogens used in the study Isolates of T. asperellum IIRRCK 1 to 4 (Kannan et al 2018) and other 4 Trichoderma isolates from the Department of Plant Pathology, ICAR-IIRR, were used for the study
The present study focused on the use of Trichoderma asperellum, its mass multiplication using commonly available organic wastes, and assessment of its efficiency in plant growth promotion and disease suppression against 2 important soil-borne pathogens of rice, viz., R. solani and S. oryzae
Summary
The results revealed that the isolate TAIK-1 of T. asperellum had the ability to release plant growth hormones and suppress the 2 major rice pathogens, viz., R. solani and S. oryzae. Chlamydospores produced by TAIK-1 help in their survival under stress conditions. Injury and nitrogen sources in the media enhanced the conidia producing ability of TAIK-1. Mass multiplication of organic substrates provided a long-term viability of TAIK-1, which can be considered for commercial storage and use
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