Molecular Diagnostics of Pathogen, Status and Management of Newly Emerging False Smut Disease of Rice in different Geographic Areas of North Karnataka

Author: Gururaj Sunkad, Shivamurthy P., Pramesh Devanna and Kasi Rao Mediga

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Abstract

Rice false smut is an important emerging biotic stress caused by the fungus Ustilaginoidea virens. Occurrence and distribution of rice false smut disease had been documented from diverse agro-climatic zones of Karnataka are still scanty. In this study, comprehensive surveys, molecular diagnostics and management of disease were carried out to know the disease status, identity of pathogen and best fungicide for the management of the disease. The survey for the disease was carried out during Kharif 2019 and 2020 in different parts of North Karnataka. The cultural and morphological characters of the pathogen were studied by using different media. The molecular characterization of the pathogen was carried out by using universal ITS primers. The field evaluation of fungicides during Kharif 2019 and 2020, followed by large-scale demonstrations and farm trials in farmer’s fields was conducted during Kharif 2021 for identification of best fungicide molecule. The results indicated the disease severity varied among different parts of north Karnataka. Potato sucrose agar (PSA) medium found to be superior for ideal growth of pathogen among different media tested. The fungus grows as acute angle branching, smooth and good mycelial growth with dark brown coloured and globular shaped chlamydospores. The DNA of U. virens was successfully amplified with universal ITS1 and ITS4 primers as well as specific uvr-F and uvr-R primers and the band size obtained was 700 bp and 350 bp, respectively. New combi fungicide molecule Trifloxystrobin 25% + Tebuconazole 50% WG @ 0.4 g/lit was very effective for the management of disease by recording lesser disease incidence and higher yields along with BC ratio in farm and large-scale demonstration trials.

Keywords

Characterization, False smut, Management, Rice, Severity

Conclusion

In the present study, the incidence of false smut varied from season to season as well as location to location. Potato sucrose agar was found ideal for growth and development of pathogen under in vitro. The pathogen was identified and characterized as U. virens based on morphological characters as well as at molecular level by using both universal and specific primers. On the basis of performance in field and farm as well as large scale demonstration trials, Trifloxystrobin (25%) + Tebuconazole (50%) 75% WG @ 0.4 g/lit was found highly effective in the management of false smut and has found a place in the university package of practices for the benefit of farmers of the region. Now, the fungicide molecule has become very popular among farmers for the management of false smut.

References

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How to cite this article

Gururaj Sunkad, Shivamurthy P., Pramesh Devanna and Kasi Rao Mediga (2023). Molecular Diagnostics of Pathogen, Status and Management of Newly Emerging False Smut Disease of Rice in different Geographic Areas of North Karnataka. Biological Forum – An International Journal, 15(8a): 197-202.