Compatibility study of bio control agents with agrochemicals under in vitro conditions

Introduction

Notable success in disease control using antagonistic microorganisms has been achieved in the laboratory, greenhouse and field over the past several years. Based on this information, there is potential to develop biological control methods for plant diseases under field conditions. Commercial formulations of various biocontrol agents are already available in the market. However, inadequate information on the performance of these antagonists under varying environmental conditions remains a major constraint to the large-scale adoption of this technology and also lack of knowledge about compatibility of bioagents with agrochemicals. There is growing interest in combining fungal biocontrol with fungicides, and research on this form of integrated control is progressing more rapidly than on other combinations of control components (Lewis and Papavizas, 1991) [3] . A novel blending technique has been reported, in which biocontrol agents were used simultaneously with seeddressing fungicides without exhibiting toxic effects on the antagonists. Integrated seed treatment with chemicals and compatible antagonists not only protects seeds and seedlings from soil-borne infections but also offers protection from seed-borne inoculum. Therefore, the use of compatible fungicides is essential for effective integrated disease management (Dubey and Patel, 2001) [2] . Considering this, the present study was undertaken to evaluate the compatibility of agrochemicals with Trichoderma isolate-1 and Pseudomonas fluorescens isolate-6, with the aim of formulating an integrated disease management approach.

Materials and Methods

The present investigation was carried out in the Main Oilseeds Research Station Laboratory, Junagadh Agricultural University, Junagadh during the year 2024-25. Compatibility study of biocontrol agents (both fungal and bacterial bioagents) with agrochemicals under in vitro conditions using Factorial Completely Randomized Design (FCRD). Evaluation of fungal (Trichoderma isolate-1) and bacterial (Pseudomonas fluorescens isolate-6) compatibility test consists of nine agrochemical treatments with four different concentrations of each treatment.

Evaluation of Compatibility of Trichoderma isolate-1 with Agrochemicals under in vitro Condition

Nine best agrochemicals with four different concentrations were evaluated against Trichoderma isolate-1 under laboratory condition following poisoned food technique of Bagchi and Das (1968) [1] . Experiment was laid out with nine treatments and each treatment repeated three times. Completely Randomized Design with Factorial concept was used for analyzing the experimental data. A control plate without poisoned medium was also maintained simultaneously to compare the growth of Trichoderma isolate-1 in treated plates. The observation on radial growth was taken when fungal biocontrol colony in control plate attain 90 mm and percent growth inhibition of fungus in each treatment was calculated by using formula given earlier in Equation (1). The details of nine best promising agrochemicals used are given in Table 1. The percent mycelial growth inhibition of the fungus in each of the treatment was calculated by using the following formula (Vincent, 1947) [6] .

Where, I = percent inhibition of mycelial growth T = Mean radial growth of test pathogen in treated plate (mm) C = Mean radial growth of test pathogen in control plate (mm)

Evaluation of Compatibility of P. fluorescens isolate-6 with Promising Agrochemicals under in vitro Condition

Nine best agrochemicals with four different concentrations were evaluated against P. fluorescens isolate-6 under laboratory condition following poisoned food technique of Bagchi and Das (1968) [1] . Experiment was laid out with nine treatments and each treatment repeated three times. 5 mm paper disc dipped in bacterial suspension placed in the centre of Petri plate. A control plate without poisoned medium was also maintained simultaneously to compare the growth of P. fluorescens isolate-6 in treated plates. Completely Randomized Design with Factorial concept was used for analysing the experimental data. The observation on radial growth was taken when bacterial colony in control plate attain 90 mm and percent growth inhibition of bacteria in each treatment was calculated by using formula given earlier in Equation ( 1). The details of nine best promising agrochemical used are given in Table 2. The next compatible treatment was Pendimethalin 30 EC showed 68.71 percent mean mycelial growth inhibition of test bioagent over rest of insecticides which were found incompatible. The interaction effect between promising insecticides and concentrations shows that, imazamox 35 + imazethapyr 35 WG found more compatible with 39.29 percent least mycelial growth inhibition at 50 ppm concentration respectively and proved significantly compatible over rest of the herbicide treatments. Pendimethalin 30 EC found next moderately compatible treatment at 50 ppm concentration and gave 48.93 percent mycelial growth inhibition. Quizalofop ethyl 10 EC at 1500 ppm concentration showed maximum mycelial growth inhibition (94.51%) of Trichoderma isolate-1 was found incompatible reaction. The results obtained in present study of promising agrochemicals with Trichoderma isolate were corroborate with more or less similar type of results as obtained by Mohiddin and Khan (2013) [4] , Saxena et al. (2014) [5] and Vyas (2020) [7] while working on Trichoderma. isolates. The data presented in Table 2 indicated that all nine agrochemicals completely inhibited the growth of P. fluorescens isolate-6 at all four different concentrations, showed an incompatible reaction with all the agrochemicals tested. The complete inhibition observed may be due either to the toxicity of the agrochemicals or to the sensitivity of P. fluorescens isolate-6.

Conclusions

On the basis of this investigation, we can conclude that fungal bio control agent under the study can be applied to crop along with fungicides or insecticides or herbicides. Among the treatments, the fungicide pyraclostrobin 13.3 + epoxiconazole 5 SE at concentrations of 50 ppm; the insecticide tetraniliprole 18.18 SC at 250, 500, 1000, and 1500 ppm; and the herbicide imazamox 35 + imazethapyr 35 WG at 50 ppm, were found to be more compatible with Trichoderma isolate-1 compared to other treatments. While bacterial bio agent was found incompatible with agrochemicals.

Acknowledgement

The authors would like to thank the Junagadh Agricultural University, Junagadh

Funding

The research was conducted with the kind and supports from Junagadh agricultural University, Junagadh

Conflict of interest

No conflict of interests exists

References

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