Exploration of Native Isolates of Metarhizium rileyi (Farlow) Samson (Ascomycetes: Hypocreales) in Maize

Author: Mamatha M., Arunkumar Hosamani, Sowmya E., Hanchinal S.G., Vijaykumar N. Ghante and Aswathanarayana D.S.

Journal Name:

Download PDF

Abstract

Metarhizium rileyi (Farlow) Samson is an important entomopathogenic fungus of more than 30 species of Lepidoptera larvae. In India, the commercial biopesticides have been suggested against different insect pests on different crops, but their application shown only a decreased efficiency credited to differences in susceptibility of target pests or non-adaptability to Indian agro-climatic conditions, and another challenging issue is non availability of region specific entomopathogenic strains. Therefore, there is a need to isolate location-specific biopesticide strains to increase the efficacy of such biopesticides for insect pest management. This study aimed to explore the new isolates of the entomopathogenic fungus, M. rileyi species across the major cropping ecosystems of Raichur and Koppal districts of kalyana Karnataka and we found consistant growth of M. rileyi throughout the year. From the survey data in Raichur district the highest number of fall armyworm (15.33/m2) cadavers were recorded at UAS, campus Raichur with 51.11 per cent incidence and in Koppal district at Gondbal village 49.25 per cent natural incidence have been recorded. Pearson’s correlation studies showed significantly positive correlation with relative humidity, minimum temperature and maximum wind speed. These isolates (UASRBC Mr-3 and UASRBC Mr-15) and its concentrations were evaluated on third instar larvae of S. frugiperda with the standard reference strain NrSf-1 from NBAIR. NrSf-1 recorded significantly highest per cent mortality (87.78 %) at 1 × 1010 spores per ml of concentration which was on par with Mr-3 (86.67 %) whereas, Mr-15 recorded 80 per cent mortality at 1 × 1010 concentration per ml. Survey data indicated that natural incidence was highest from July second fortnight to December first fortnight. Later the infection rate gradually reduced with the decrease of precipitation, relative humidity and increase in temperature. Isolate UASRBC Mr-3 was more virulent with 86.67 per cent mortality which is on par with NBAIR isolate NrSf-1 with 80.66 per cent mortality against S. frugiperda, These isolate should be formulated as a myco-insecticide and tested under field conditions in further studies.

Keywords

Metarhizium rileyi, Exploration, Spodoptera frugiperda, virulent

Conclusion

In Raichur district the survey was conducted to record the natural incidence of M. rileyi in maize crop. Highest number of fall armyworm (15.33/m2) cadavers were recorded at UAS, campus Raichur with 51.11 per cent incidence. Whereas in Koppal highest S. frugiperda cadavers (11.0/m2) were noticed in Gondbal village with 49.25 per cent natural incidence. Pearson’s correlation studies showed that during 2020-21 the natural infection was significantly positive for minimum temperature, rainfall and maximum wind speed and there was negative correlation with maximum temperature for natural infection in Raichur and Koppal. Isolate UASRBC Mr-3 was more virulent with 86.67 per cent mortality which is on par with NBAIR isolate NrSf-1 with 80.66 per cent mortality against S. frugiperda UASRBC Mr-3 isolate should be formulated as a myco-insecticide and tested under field conditions in further studies. From results showed that the EPF M. rileyi isolates were the most pathogenic to S. frugiperda larvae. The results presented in this study increase the knowledge about natural zoonosis of M. rileyi on different lepidopteran pests and open new avenues for studies regarding the virulence against S. frugiperda larvae.

References

-

How to cite this article

Mamatha M., Arunkumar Hosamani, Sowmya E., Hanchinal S.G., Vijaykumar N. Ghante and Aswathanarayana D.S. (2023). Exploration of Native Isolates of Metarhizium rileyi (Farlow) Samson (Ascomycetes: Hypocreales) in Maize. Biological Forum – An International Journal, 15(4): 668-677.