Exploring the potential of saline-tolerant Streptomyces for managing blast disease in rice (Oryza sativa L.)

Rice (Oryza sativa L.) is recognized as one of the world’s most important staple food crops. Yield loss due to diseases is one of the major constraints in rice cultivation. Among them, the blast disease caused by Magnaporthe oryzae ranks first in affecting the rice crop. Hence, the present study proposed to study the efficacy of antagonistic activities of Streptomyces spp. against blast disease in rice. Twenty isolates of the antagonistic Streptomyces sp. were isolated from rhizosphere soil. From the sequence analysis of 16s rRNA of isolate TRYS 10 was identified as Streptomyces caelestis. Antagonistic activity assay was conducted using a dual culture technique for blast pathogens. The isolates S. caelestis (TRYS 10) and TRYS 16 were effective against blast and recorded the inhibition zone of 19 and 15.2 mm, respectively followed by TRYS 5 (9.0 mm). An isolate S. caelestis (TRYS 10) induced the growth promotion of rice viz, root length (16.72 cm), shoot length (22.13 cm) and vigour index (3807). S. caelestis (TRYS 10) was tested for its efficacy against blasts under greenhouse conditions. Disease severity of blast in pathogen-inoculated control plants was 8.89 %, while in Streptomyces + pathogen-inoculated, it was 2.22 %. A foliar spray of S. caelestis (TRYS 10) at the time of symptom appearance and repeated 15 days later was found to be effective in reducing blast in rice up to 42.64 % under field conditions. Two sprays of S. caelestis at the time of initial appearance of blast disease and 15 days later reduced the disease incidence as well as improved the plant growth and yield in rice.