Indexing

Pathogenic variability of Rhizoctonia bataticola and Sclerotium rolfsii isolates of Groundnut (Arachis hypogeae L.) in Andhra Pradesh

Author: T. Ganesh, K. Vemana, B.V. Bhaskara Reddy, N.C. Venkateswarlu, A. Sri Vidhya, R. Sarada Jayalakshmi Devi and K.S.S. Naik

PDF Download PDF

Abstract

Groundnut is an important oil seed leguminous crop which is affected by several fungal, viral and phytoplasmal diseases. Among the fungal diseases, soil borne diseases viz., dry root and stem rot incited by Rhizoctonia bataticola and Sclerotium rolfsii respectively are the most important as they possess the major threat to the crop in all the stages of crop and causes higher yield loss. The soil borne fungal pathogens survives in the soil for many years in the form of microsclerotia and sclerotia and causing soil borne fungal infections when the conditions are favorable. The current study was conducted to know the pathogenic variability (virulence) among these pathogens. Dry root rot and stem rot affected samples were collected from the major groundnut growing areas of Rayalaseema region of Andhra Pradesh and isolated the pathogens. A total of 44 Rhizoctonia bataticola and 40 Sclerotium rolfsii isolates were isolated and purified and tested the pathogenicity under glasshouse conditions at ARS, Kadiri by following the sick soil inoculation method with mass multiplied pathogen(s) inoculum on sorghum grains. The results revealed that the isolate of GNRb-2 of Rhizoctonia bataticola and GNSr-25 of Sclerotium rolfsii isolate were found significantly more virulent with maximum of 89.4 and 95.8 percent disease incidence respectively and the isolates GNRb-5, GNRb-17, GNRb-29 of R. bataticola and GNSr-24 of S. rolfsii were recorded the least percent disease incidence with 13.3 and 13.3 respectively, when compared with other isolates tested. Further the isolates were categorized into the non-pathogenic, weekly pathogenic (WP), moderately pathogenic (MP, strongly pathogenic (SP) and highly/ aggressively pathogenic (HP/AP) based on their percent disease incidence (PDI) on the susceptible host cv. Kadiri-6.

Keywords

Groundnut, Rhizoctonia bataticola, Sclerotium rolfsii, Pathogenic variability.

Conclusion

The plants showing the typical symptoms of the dry root rot and stem rot were collected from the major groundnut growing regions of the Andhra Pradesh viz., Anantapuramu, Chittoor, YSR Kadapa, Kurnool and SPSR Nellore districts. A total of 44 No’s of Rhizoctonia bataticola and 40 No’s of the Sclerotium rolfsii isolates were isolated from the field collected samples and were tested for their pathogenic variability. The R. bataticola and S. rolfsii isolate(s) viz., GNRb-2 and GNSr-25 isolates showed the maximum percent disease incidence of 89.39 and 95.83 respectively. The isolates viz., GNRb-5, GNRb-17, GNRb-29 of R. bataticola and GNSr-24 of S. rolfsii were recorded the lowest disease incidence with 13.33 and 13.33 respectively, when compared with other isolates tested. Further the isolates were categorized into the non-pathogenic, weekly pathogenic (WP), moderately pathogenic (MP, strongly pathogenic (SP) and highly/ aggressively pathogenic (HP/AP) based on their percent disease incidence (PDI) on the susceptible host (K-6 groundnut cultivar). Among the isolates tested for R. bataticola the non-pathogenic were found as zero or nil, whereas WP were found as 4 and 13, MP as 21 and 18, SP as 15 and 16 and HP as 3 and 4 in Rhizoctonia bataticola and Sclerotium rolfsii respectively. The categorization of the pathogen isolates will help to understand the virulence pattern of the pathogens. Further it was helpful to study the major factors responsible for their variation in the pathogenicity at the genomic level.

References

-

How to cite this article

T. Ganesh, K. Vemana, B.V. Bhaskara Reddy, N.C. Venkateswarlu, A. Sri Vidhya, R. Sarada Jayalakshmi Devi and K.S.S. Naik (2023). Pathogenic variability of Rhizoctonia bataticola and Sclerotium rolfsii isolates of Groundnut (Arachis hypogeae L.) in Andhra Pradesh. Biological Forum – An International Journal, 15(8a): 352-358.