RANGASWAMY, K. T.SAHANA, N. BANAKAR2020-10-032020-10-032018-10-30Th-12212https://krishikosh.egranth.ac.in/handle/1/5810152280Rice is an important food crop cultivated all over the world. India occupies first and second position in area and production respectively. Fungicidal stress which is abiotic stress and blast disease a biotic stress, are constrains in the rice production. This study aimed at managing these stresses through tropical red seaweed (Kappaphycus alvarezii) bioformulations (LBS-6 and LBD-1). Foliar application of fungicides alone led to negative physiological changes (stomatal closure and leaf temperature) which were positive in combinations. Biochemical analysis of ROS, antioxidants and plant minerals revealed that the seaweed bioformulations alleviated the production of H2O2 and O2 -1 due to fungicidal stress by inducing the activity of antioxidants viz., APX, CAT, GR, POD and SOD. Increased levels of Ca+ and K+ interacted with cellular signalling systems of ROS and stomatal closure respectively. RNA sequencing revealed the growth and defence related expression of genes in different treatments. A total of 3498 differentially expressed genes (DEG’s) were identified. Among them 1116 DEG’s were specifically regulated in MG-01 inoculated treatments. Gene expression using qPCR showed the increased expression levels of OsPR1#012, OsPR1#021, OsPR1#022, OsPR1#074, OsPR1#121, PAL-6, PR1-5 and PR-15 transcripts and least disease severity in plants primed and challenge inoculated with MG-01 under glass house condition. Expression level of different stress transcripts viz., E2F, HSFA2A, HSFB2B, HSFB4C, HSFC1A and ZIP12 was less in case of combination treatments compared to sole application of fungicides. LBD-1 a defence bioformulant was found to be on par with tricyclazole in curtailing the blast disease under field condition. Increased chlorophyll content, leaf area, plant height, productive tillers and panicles were recorded in LBS6 treated plants. Results of tricyclazole residue analysis revealed that, seaweed bioformulations were efficient in drastic reduction of tricyclazole residue (0.016 mg Kg-1 ) in rice grains. Overall growth and yield parameters directly impacted on straw and grain yield.EnglishThesis