Root Colonization of Rice by Serendipita indica and Azotobacter chroococcum and their Soil Enzyme Activity

ABSTRACT: Serendipita indica is a root endophytic fungus that promotes overall plant development by forming a symbiotic relationship with the roots of vascular host plants. Azotobacter is a Gram-negative, motile, aerobic, free-living bacteria, used as a biofertilizer, improves seed germination, overall plant development and yield of various crops. In this paper, we are evaluating the impact of combinatorial effect of Serendipita indica and Azotobacter chroococcum on root colonization and soil enzyme activity of Oryza sativa. The study utilized cultures of S. indica and A.chroococcum grown in jaggery- based broth for bulk multiplication. Tests in the field were carried out during May–October 2023, with treatments: Control (C), T1 (A. chroococcum), T2 (S. indica), and T3 (combination) with 3 replicates and approximately 100 plants each replicate. Root colonization was examined using Trypan blue staining, and soil enzyme activities (alkaline phosphatase, urease, and dehydrogenase) were measured following standard protocols. This study evaluated the effects of Serendipita indica and Azotobacter chroococcum on soil enzymes in two rice types i.e. PB1121 and PB1718. PB1718 exhibited higher soil dehydrogenase activity, while PB1121 showed greater increases in alkaline phosphatase and urease activities. In PB 1121, the combined treatment of S. indica and A. chroococcum significantly boosted soil dehydrogenase (148.2%), urease (89.5%), and alkaline phosphatase (109.9%) activities, demonstrating strong synergy. Similarly, in PB 1718, these activities increased 219.8, 70.5 and 27.2%, respectively, with a greater rise in urease and phosphatase in PB 1121, while PB 1718 exhibited a higher enhancement in dehydrogenase activity.. The in-depth analysis provides valuable insights into synergistic effect of S. indica and A. chroococcum on plant root system and soil enzyme activity.