ABSTRACT

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Ishimiya) Swings et al., is one of the destructive diseases of rice in all the major rice growing of regions India. Use of antibiotics are the common practice for the management of BLB, which have detrimental effect on human health and to environment. An attempt was made to isolate actinobacteria from the rice rhizosphere soil, to characterize and identify the potent isolates for management of BLB. From different agroclimatic zone viz., zone 3, zone 8 and zone 9 of Karnataka, total of thirty two actinobacterial isolates were isolated. By dual culture technique, all isolates were evaluated under primary and effective eight isolates were selected based on qualitative observation of pathogen inhibition and were further subjected to secondary screening. In secondary screening among eight effective isolates AUDT-502 (Streptomyces rimosus) produced a maximum zone of inhibition (1.86 cm) followed by DWD-9 (1.76 cm) and GVT-1 (1.44 cm). The potent actinobacterial isolates are characterized morphologically and biochemically. All three isolates morphologically differ w.r.t., colour, colony shape and mycelial pigmentation and showed positive results for gram staining, catalase test, HCN, IAA, siderophore production and phosphates solubilization and negative for 3% KOH test. 16 S rDNA sequencing the potent isolate viz., DWD-9 identified as Streptomyces capoamus and GVT-1 as Streptomyces cavourensis and AUDT-502 was previously identified as Streptomyces remosus. Under glasshouse, consortia of AUDT-502+ DWD-9+ GVT-1 @ 108 cfu/ml as seed treatment, seedling dip and foliar sprayed plants showed the least lesion length (4.01 cm) and PDI (31.11) followed by viz., ADUT-502, DWD-9 and GVT-1 treated plates as through seed treatment, seedling dip and foliar spray showed the reduced disease and respective treatments showed the improved growth parameters such as plant height, number of tillers per plant, root length and dry root weight.