In-vitro Evaluation of Efficacy of Trichoderma harzianum on the Radial Growth of Alternaria alternata

Stevia rebaudiana Bertoni, a herbaceous perennial known for its natural sweetness, has garnered global recognition and is found in various regions of India. A study was carried out to investigate the leaf spot disease in Stevia, caused by Alternaria alternata (FR.) Keissler to find out the most suitable design of dual culture technique. Since the leaves are the primary site for synthesizing sweet glycosides, in Stevia this disease leads to significant losses and ultimately reduces the yield which leads to a serious concern. Due to the harmful effects of chemical fungicides, finding a safer alternative to control the pathogen became a priority. This prompted experiments with bioagents for pathogen control. Bio fungicides derived from Trichoderma are increasingly being recognized as successful agricultural applications, with over 50 registered products available worldwide. The present study was conducted in the Laboratory, Department of Plant Pathology, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj (Uttar Pradesh). The dual culture technique was carried out on Completely Randomized Design (CRD) with three replications and six treatments. Examination of fungal colony characteristics was done through microscopic examination. At 7 DAI, maximum mycelial inhibition of 96.70% was recorded in the treatment T6 (six discs of Trichoderma harzianum against one disc of Alternaria alternata).