Studies on Bipolaris oryzae (Shoemaker), the Incitant of Brown Spot of Rice and its Management
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Date
2023-07
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G. B. Pant University of Agriculture & Technology, Pantnagar-263145
Abstract
Rice (Oryza sativa L.) is the major crop cultivated all around the world and
considered as the staple food. The cultivation is impeded by a number of insect-pests and
diseases causing a huge economic loss. Brown spot of rice caused by Bipolaris oryzae
(teleomorph : Cochliobolus miyabeanus) is one of the major fungal disease leading to
significant reduction in quality and quantity of produce. The present investigation was
carried to study the variability in the pathogen, in-vitro and field management of the
disease and activity of defence related enzymes in response to application of bio-agents.
The morphological and molecular variability was studied in isolates obtained from
different tehsils of Udham Singh Nagar district. A significant variability was resulted from
the isolates of the pathogen in a district. For the management of disease, seven fungicides
and four biocontrol agents were tested both under in-vitro and field conditions. Among the
fungicides, Tebuconazole 25.9%EC resulted to be the best by inhibiting the maximum
mycelial growth under in-vitro conditions and leading to maximum reduction of disease
index under field conditions. However, under in-vitro conditions T. harzianum (Pant
bioagent-1) was found to the most effective bioagent followed by P. fluorescens (Pant
bioagent-2) and under field conditions, the minimum disease index and maximum yield
was obtained with the combination of T. harzianum and P. fluorescens (Pant bioagent-1
and Pant bioagent-2). The activity of three defence related enzymes i.e., Phenylalanine
ammonia lyase (PAL), Peroxidase (POD) and Polyphenol oxidase (PPO) was found to be
maximum in the treatment with spray application of T. harzianum. An integrated
management approach with use of effective bioagents and fungicides should be
recommended for the disease management.
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Theses of M.Sc.