Studies on compatibility and combined efficacy of microbialconsortia for the management of major diseases in coconutand citrus

The study was aimed to develop microbial consortia for the management of major diseases in coconut and citrus. The primary screening of rhizosphearic bacteria showed that Pseudomonas spp., Bacillus spp. and fungi Trichoderma spp. are found effective against test pathogens viz., Ganoderma lucidum, Thielaviopsis paradoxa, Phytopthora paradoxa, Lasiodiplodia theobromae from coconut, and Fusarium solani from citrus. Fungal and bacterial antagonists are found compatible without zone of inhibition. Efficacy of non-volatile compounds are found with increasing trend with increase in concentration of 10, 25, 50 and 75 per cent in individual consortia as well as combined consortia. Non volatile compounds of mixed consortia composed of bacterial consortia + fungal consortia exhibited the superior inhibition against test pathogens compared to the individual consortia. At 75 per cent as highest concentration, inhibited the pathogens in the order of T. paradoxa (90.28%), Ganoderma lucidum (89.44%), Fusarium solani (82.50%), Lasiodiplodia theobromae (81.94%) and Phytophthota palmivora (81.39%). Volatile compounds of bacterial consortia - T8 (Pf-A, Pst-A and Bs-T1) and fungal consortia -T4 (Tr-A, Th-A, Ta-A) are recorded the superior inhibition when compared to the individual bio agents. The bacterial consortia T8 recorded the superior inhibition on test pathogens in the order of Ganoderma (85.28%), Fusarium (75.28%), Thielaviopsis (71.94%), Phytopthora (71.67%) and Lasiodiplodia (67.50%) compared to the individual bio agents. Similarly, the fungal consortia showed the superior inhibitory effect on test pathogens in the order of Ganoderma (83.25%), Phytopthora (82.50%), Lasiodiplodia (83.06%) Fusarium (80.56%), and Thielaviopsis (73.61%). Compatibility of 3 bacterial and 3 fungal bio agents were evaluated in various combinations, no zone of inhibition was observed in any case and hence they may be mixed in preparing formulations. Screening of substrate for multiplication of bio agents revealed that superior CFU population ranged from 3.36 to 9.43 x 106 CFU and 20.62 x 108 CFU is recorded on neem cake at 7 days of incubation period by Trichoderma spp. and bacterial bio agents, respectively. Visual observations of substrates for mass multiplication on neem cake, farm yard manure, vermicompost, coir pith and press mud indicated that thick spur of green colour mycelial growth observed on neem cake indicated excellent grade followed by FYM (Average), vermicompost (good), coir pith (average) and press mud (poor). Shelf life study of promising bacterial bio agents + fungal bio agents in consortia as talc formulation indicated that all the bacterial CFU count recorded in 106 dilution for a period of 90 days and declined to 105 at 120 days whereas fungi it was below the 105 dilution at 120 days. Hence, the mixed consortia were found to be best for field use before 120 days.