INTRODUCTION Groundnut is one of the major edible oil seed crops of Andhra Pradesh, occupying 0.66 M ha of area with 0.85 M t of average production and 1.28 t ha-1 of average productivity. Majority of groundnut crop in Andhra Pradesh is cultivated during kharif in Anantapuramu, Chittoor, Kurnool and Kadapa districts. Several biotic and abiotic factors are the causes of low productivity (1.28 t ha-1) of groundnut in A.P (Directorate of Economics and Statistics, 2019-20). Pattee and Young (1982) reported that, M. phaseolina can cause pod, root, peg, stem and leaf spots on older and younger seedlings. The congenial conditions for the development of the disease are soil temperature of 80-95oF prevailing for two to three weeks. The pathogen is primarily soil borne and transport of implements, irrigation water and grazing animal from the infected field to healthy field transmits the disease. The air borne pycniospores also acts as potential dispersing agent for the pathogen (Rangaswami and Mahadevan 2008). The current indiscriminate use of toxic chemicals alone to reduce the disease incidence resulted in environmental deterioration, additional financial burden to the farmer and fungicidal resistance development in the pathogen (Rudresh et al., 2005). Considering the above demerits of using toxic chemicals to manage the disease, inclusion of biological control in the disease management has the good potential to ameliorate the environmental risks, provides long lasting management and reduces the chances of resistance build up in the target pathogen. Use of consortia formulation of potential biocontrol agents like PGPR bacteria and antagonistic fungi is the recent advancement in the field of plant protection. This approach besides controlling the diseases, increases the nutrient uptake, phosphorous solubilization and uptake, plant growth and finally the yield. MATERIALS AND METHODS Pathogen, M. phaseolina isolation. The standard tissue segment method as described by Rangaswamy and Mahadvan, (1999) was followed for isolation of the pathogen from the infected plant sample. The isolation includes cutting a small bit of host root tissue having both infected and healthy portions using sterilized scalpel. The cut pieces were kept for two minutes in one per cent sodium hypochlorite and washed thrice with sterile distilled water. The resultant root pieces were inoculated on to Petri plates containing sterilized potato dextrose agar (PDA) medium and incubated at 28 ± 2°C. The Petri plates were regularly inspected for the growth of the fungal pathogen and pure culture of the same was maintained following single hyphal tip method. PDA slants were used to store the pure cultures of the test pathogen. Identification and morphological characterization of M. phaseolina. The morphological description of Barnett and Hunter, (1972) were followed for identification of M. phaseolina. The compound microscope (ACCU SCOPE-EX 30) was used to study the hyphal branching pattern, size and shape of microsclerotia. Biocontrol agents isolation. The Trichoderma spp. were isolated form the rhizosphere soil of groundnut following serial dilution technique on Trichoderma Specific Medium (TSM) (Johnson and Curl 1977). The bacterial biocontrol agent, P. fluorescens isolates were isolated form the rhizosphere soil of groundnut and were purified following streak plate method. The isolated bacteria was found gram negative and emitted fluorescent light when illuminated with UV light. (Manjunatha et al., 2012). Trichoderma spp. taxonomic identification The six isolates of Trichoderma spp. were classified up to species level using the Trichoderma morphological descriptions of Bisset, (1984, 1991 a, b, c). To do so, the characters of conidiophore branching, phialide shape, phialide grouping, chlamydospore formation, spore balls, conidial shape and sterile appendages were considered. In vitro dual culture studies of biocontrol agents against M. phaseolina In vitro fungal antagonist-test pathogen interaction. The standard dual culture technique described by Morton and Straube (1955) was followed for assessment of effectiveness of Trichoderma isolates against M. phaseolinain vitro. The test was conducted by inoculation of 5 mm mycelial discs of both the test pathogen and the fungal biocontrol agents opposite to each other form one cm away from the periphery of Petri plate containing PDA. When the test pathogen was fully occupied the control plate, the results of the dual culture were recorded. Bacterial antagonist-test pathogen interactions in vitro. The P. fluorescens isolates were tested for their effectiveness against M. phaseolinain vitro following dual culture method. In a Petri plate containing equal amounts of PDA and NA, the antagonistic bacterium was inoculated as two streaks of 5 cm opposite to each other one cm away form the periphery and the test pathogen was inoculated as five mm mycelial disc in the middle. The monoculture of the test pathogen was maintained as the control for comparison. The results were recorded as the zone of inhibition in the dual culture plates when the pathogen in the monoculture was fully grown. The formula given by Vincent (1927) was used to obtain the per cent inhibition exhibited by the bacterial biocontrol agent against mycelial growth of test pathogen in the dual culture plates. where, I = Per cent reduction in growth of test pathogen. C = Radial growth (mm) in monocultured check. T = Radial growth (mm) in dual cultured plates. In vitro compatibility studies between bacterial and fungal antagonists Dual culture studies were conducted to test the compatibility between bacterial and fungal antagonists as described by Morton and Stroube (1955). The Petri plate containing equal amounts of PDA and NA was inoculated with fungal and bacterial biocontrol agents as 5 mm mycelial disc in the middle and 5 cm streaks at one cm away from the periphery of the plate on either side of the fungal mycelial disc respectively. The Petri plates containing the pathogen was treated as control. The plates were incubated at 25 ± 2°C and observations from the dual cultured plates were recorded when the pathogen in the control plates was fully grown. The standard formula by Vincent (1927) was used to obtain the percent inhibition of fungal biocontrol agent by bacterial biocontrol agent. where, I = Per cent reduction in growth of test pathogen. C = Radial growth (mm) in monocultured check. T = Radial growth (mm) in dual cultured plates. M. phaseolina mass multiplication. Sterilized sorghum grains were used as substrate for mass multiplication of M. phaseolina. The clean sorghum grains were soaked in solution containing 4 per cent dextrose for overnight. Later the solution was drained and the grains were dried to appropriate moisture levels. The dried sorghum grains were filled up to 2/3 volume of 250 ml conical flasks and autoclaved at 15 p.s.i. for twenty minutes. The sterilized sorghum grains were inoculated with four day old 5 mm mycelial discs of test pathogen and kept for incubation. Talc based formulations of potential antagonists. The sterilized potato dextrose broth (PDB) was inoculated with three-day old Trichoderma culture and kept agitated by placing inside shaking incubator for seven days to get increased biomass production. Nutrient broth (NB) was inoculated with two loops full of bacterial antagonist and kept in shaking incubator for continuous agitation for three days for increased biomass production. The standard procedure was followed to develop talc formulations of both bacterial and fungal biocontrol agents (Vidhyasekaran and Muthamilan, 1995). Effective Trichoderma isolate formulation in paraffin oil + soybean oil (1:1). Effective Trichoderma sp. isolate was formulated using paraffin oil + soybean oil (1:1) liquid carrier material. For this, dry spores of Trichoderma were harvested from solid substrate (Trichoderma mass multiplied on sorghum grains) after 12 days of incubation using 100 mesh sieve. Two grams of dry spore was aseptically transferred into pre-sterilized 100 ml of liquid carrier containing paraffin oil + soybean oil (1:1). Later the formulation was poured into glass bottles and stored at 4oC in a refrigerator (Sathiyaseelan et al., 2009). Formulation of effective P. fluorescens isolate in glycerol. Solution containing two per cent glycerol in NB was used as liquid carrier material for formulation of effective isolate of P. fluorescens. The formulation was prepared by mixing 1 ml of effective bacterial antagonist at log phase and kept for incubation for two days. Later the formulation was stored in refrigerator at 4oC (Manikandan et al., 2010). Glass house studies on management of M. phaseolina using effective isolates of bacterial and fungal antagonists. The experiment was designed to test the performance of chemical and formulation of biocontrol agents in managing dry root of groundnut in pot culture. The table below shows the design of the CRD. Completely Randomized Design (CRD) statistical method was followed with groundnut test variety Narayani for finding effectiveness of above treatments in the management of groundnut dry root rot. The observations recorded were, PDI, final plant population, initial plant population, dry weight and fresh weight, shoot length and root length of groundnut plants. RESULTS AND DISCUSSION The pathogen, M. phaseolina The disease samples of groundnut dry root rot were collected from Sangam, Somasila areas of SPSR Nellore Dt. and R.A.R.S Tirupati, Rangampeta areas of Chittoor Dt. of Andhra Pradesh. The isolates collected from Sangam, Somasila, R.A.R.S Turuapti, Ramgampeta are named as SgMp, SmMp, TpMp and RgMp respectively. The different isolates of M. phaseolina were isolated following tissue segment method and single hyphal tip purification technique on PDA (Ghewande et al., 2002). The isolates RgMp, SgMp and SmMp produced partially fluffy mycelium whereas isolate TpMp produced highly fluffy mycelium in culture. Morphological studies to characterize M. phaseolina isolates were conducted by observing 10 d old culture grown on PDA medium. Mycelia of for RgMp, TpMp and SgMp appeared white fluffy in the beginning and grey at maturity but the mycelia of SmMp appeared black at maturity. The microscopic examination of fungal mycelia revealed characteristic right angular branching pattern of M. phaseolina. The average microsclerotial size of SmMp was 94.30 µm which was bigger among four isolates followed by RgMp (91.80 µm) and TpMp (85.80 µm). Smaller microsclerotia were observed in isolate SgMp (70.82 µm). The microsclerotia of all isolates were blackish brown in colour. The test pathogen exhibiting all the above characteristics was identified as M. phaseolina (Tassi.) Goid. The results were similar with the works of Subramanayam (1971) who morphologically characterized M. phaseolina. Native rhizosphere isolates of antagonistic Trichoderma spp. Six isolates of Trichoderma spp. were isolated from different soil samples of Chittoor and SPSR Nellore districts. The Trichoderma selective medium was used for initial selective isolation and PDA was used for further purification and storage of the fungal antagonist. The isolates of Chittoor were named as GRT1, GRT2, GRT3 and Nellore as GRT4, GRT5 and GRT6. Using ACCU-SCOPE-EX 30 microscope, the Trichoderma isolates were characterized up to species level by considering the characters of conidiophore branching, chlamydospore formation, structure and distribution of phialides, size and shape of conidia. Form the study conducted, two species of Trichoderma were identified i.e., T. viride (GRT2, GRT5) and T. harzianum (GRT1, GRT3, GRT4 and GRT6). Native rhizosphere isolates of antagonistic P. fluorescens. Five isolates of antagonistic P. fluorescens were isolated from rhizosphere soil samples of groundnut collected from different places in Chittoor (PF1, PF2, PF3) and SPSR Nellore (PF4, PF5) districts. King’s B medium was used for selective isolation of P. fluorescens and PDA was used for further purification and maintenance. The bacterial isolates were confirmed as P. fluorescens as the cells were gram negative and emitted fluorescens under UV light. The results were similar with the findings of Elangovan and Gnanamanickam (1990). Interaction between Trichoderma spp. and M. phaseolina. Dual culture technique was performed to study interaction between Trichoderma spp. and M. phaseolina in vitro. Two factorial CRD was used to analyze the results as shown in Table 1. we observed Trichoderma isolates GRT5 (67.92%), GRT6 (61.25%), GRT1 (59.17%) and GRT4 (60.42%) recorded maximum inhibition percentage when tested against RgMp, TpMp, SmMp and SgMp. Trichoderma isolates, GRT1, GRT2, GRT4 and GRT 5 were found effective in inhibiting the mycelial growth of M. phaseolina while the pathogen isolate SmMp appeared as virulent pathogen by showing minimal inhibition percentage (56.81 %). Kumari et al. (2022) recorded highest mycelial growth inhibition of M. phaseolina, the causal agent of dry root of chickpea by T. harzianum (73.33) which outperformed over other biocontrol agents under the study. Interaction between P. fluorescens and M. phaseolina. Dual culture technique was performed with five isolates of P. fluorescens and four isolates of M. phaseolina to find the effective isolates of bacterial antagonist in vitro. Two factorial CRD was used for analysis of results as presented in the Table 2. We observed that, PF4 isolate of P. fluorescence recorded maximum inhibition percentage against RgMp (37.04%), SgMp (38.52%), SmMp (31.85%) and PF3 isolate against TpMp (39.26%). The two isolates of antagonist i.e., PF3 and PF4 were found effective in inhibiting the growth of M. phaseolina with maximum inhibition while the pathogen isolated SmMp was identified as virulent pathogen isolate with minimum inhibition (15.26 %). In a study conducted by Shanmugam et al. (2002), it was found that, Pf 1 isolate of P. fluorescens was significant in reducing the growth of M. phaseolinain vitro. Compatibility studies between effective isolates of P. fluorescens and Trichoderma sp. We obtained successful combination of antagonistic fungal (GRT4) and bacterial (PF4) isolates with minimum negative interaction (21.48 %) from the dual culture studies in vitro. Mishra et al. (2013) reported that the PBAP-27 isolate of Pseudomonas and PBAT-43 isolate of Trichoderma were found most compatible with least negative interactions in vitro. The same combination was used for developing mixed formulation. Formulations of isolate GRT4 of T. harzianum and isolate PF4 of P. fluorescens. For solid formulations of bacterial and fungal antagonists talc was used as solid carrier material and paraffin oil + soybean oil (1:1) and glycerol as liquid carrier material. For control of chickpea root rot Gaur et al. (2005) used talc formulation of T. harzianum and obtained better results. Management of groundnut dry root rot using bioformulations of P. fluorescens (PF4) and T. harzianum (GRT4) The mass multiplied test pathogen on sorghum grains was applied as 100 g kg-1 of soil in pots and treatments were imposed in different combinations of biocontrol agents and chemical to test for the best performing treatment. At 45 DAS the biometric observations like root length, shoot length, dry weight, fresh weight were recorded along with germination percentage, final plant population, initial plant population and per cent disease incidence (PDI) of dry root rot. Impact of treatments on biometric parameters of groundnut plant (a) Root length. It was observed that, treatment T10 showed increased root length (34.44 cm) followed by T9 and T8 (31.97, 29.99 cm respectively). Jayasree et al. (2000) observed similar effects on shoot and root lengths of sesame and black gram with combined application of bacterial and fungal biocontrol agents. (b) Shoot length. Similar with the root length, the treatment T10 again recorded highest shoot length (22.39) followed by treatments T9, T8 and T2 (22.16, 21.92 and 19.57 cm respectively). As presented in the Table 4, T12, the control treatment recorded 6.04 cm of shoot length which was lowest among all treatments tested. Aiswarya et al. (2022) reported that seed treatment of groundnut seeds with T. viride @ 10 g kg-1 and P. fluorescens @ 10 g kg-1 against collar rot pathogen Aspergillus flavus showed increased seedling lengths of 17.07 cm and 16.89 cm respectively over control (16.04 cm). (c) Fresh weight and dry weight. Treatment T10 recorded highest fresh weight of 10.72 g and treatment T9, T8 and T11 found next best treatments with 9.42, 8.91 and 7.75 g respectively. The dry weight was highest in the pots imposed with treatment T10 followed by T9 and T8 (2.16, 1.86 g respectively). Treatment T12, the control yielded lowest dry weight of 0.76 g. Martínez-Salgado et al. (2021) reported increased growth of groundnut plants (1417.60 g) and low disease incidence (76 %) with the application of T. koningiopsis (T-K11) @1 × 108 conidia mL−1 at 16 days after sowing on seedlings. Germination percentage. The treatment T10 recorded highest germination percentage of 96.67 per cent and treatments T9, T8, T11 and T2 stood next with germination percentages of 93.33, 90.00, 86.67 and 83.33 per cent respectively as represented in Table 3. The germination percentage was very poor in the control treatment T12 (53.33 %). Mishra et al. (2013) found that higher germination percentage (72.11 %) was recorded in soybean and chickpea plants treated with combined bioformulation of PBAT-43, PBAP-27 isolates of Trichoderma and Pseudomonas respectively. Effect on groundnut plant population. The treatment T10 recorded highest initial (9.67) and final (9.33) plant population followed by T9, T8, T11 and T2. The control treatment T12 recorded least plant population (1.33). Effect on dry root rot disease. Lowest dry root rot disease incidence (3.70%) was observed in T10 treatment and T9, T8 treatments were also shown to be promising treatments with minimal disease incidence of 7.41 and 11.20 per cent respectively. The disease incidence was very high (76.67 %) in control treatment. Ramesh and Korikantthimath (2006) observed same effect on groundnut dry root incidence with combined use of P. fluorescens and T. viride.