IDENTIFICATION OF POTENTIAL ISOLATES OF Nomuraea rileyi AND DEVELOPMENT OF FORMULATIONS
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The roving survey was taken up at monthly intervals in two agricultural zones viz., Southern and Krishna zones of Andhra Pradesh from November 2014 to February 2015 for the occurrence of N. rileyi, an entomopathogenic fungus. Among the crops and villages surveyed, at Narakoduru village of Guntur district in Krishna zone, the fungal infected S. litura cadavers were observed in cotton, in considerable number from December 2014 to February 2015. And also, in rabi groundnut crop, at Kandriga village of Chittoor district (Southern zone), the fungal infected cadavers were noticed during December 2014 - January 2015.
The cadavers were identified based on white mycelial mat or light green colour sporulation covered throughout the body except on the head capsules. They were also identified based on characteristic adhering nature to the plant parts. By studying the characters of fungus, laboratory confirmation was done.
The molecular characterization of 5 isolates of N. rileyi was done by RAPD-PCR for studying genetic variability/similarity. RAPD banding profiles with 10 different random primers viz., 5 primers from OPM, 4 primers from OPA, one primer from OPD revealed the existence of genetic variability to a considerable extent among the five isolates. These primers showed 52.02% polymorphism as all the bands obtained were polymorphic with size ranging from 100 bp to 3000 bp. Jaccards similarity co-efficients between the N. rileyi isolates produced shows 88.00 per cent genetic variation between isolates of Nr-7 (Narakoduru) and Nr-2 (V.Kota-1), closely followed by Nr-1 (Tirupati)
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and Nr-7 (V.Kota-1) (78.00%). While the isolate Nr-2 (V.Kota-2) and Nr-7 (Narakoduru) were found to be genetically more similar than other combinations.
Eleven formulations of N. rileyi (six grain formulations and five wettable powder formulations) were prepared in the Department of Entomology, S.V. Agricultural College, Tirupati during 2014-15. The formulations prepared were stored at 22°C and the viability, virulence studies (against H. armigera) were carried out at 15 days intervals up to 60 days. For the virulence studies, third instar larvae of H. armigera was used as the host insect.
Among the different formulations of N. rileyi made with grains, maize grain formulation recorded highest viability and virulence of 84.73 and 59.70 per cent, respectively. Lowest viability and virulence were recorded in ragi grain formulation (66.37 and 37.00 per cent, respectively).
Among the wettable powder (WP) formulations, (made flours as carrier material), maize flour formulation recorded highest viability and virulence of 84.37 and 71.66 per cent, respectively at 60 days of preparation. The remaining formulations i.e., rice flour, wheat flour, sorghum and bajra flour as inert material shown the viability and virulence ranging from 65.87-88.20 and 34.00 to 69.33 per cent respectively.
Both grain formulations and wettable powder formulations of N. rileyi were found almost equal in recording the viabilities and virulence.
In the field, when different formulations were evaluated against larvae of H. armigera, maize grain formulation recorded highest (72.33) per cent of larvae reduced 15 days after treatment. Formulations with maize flour and rice grain as carriers were found to be next best against the larvae of H. armigera. The remaining formulations i.e., sorghum grain, wheat grain, bajra grain, ragi grain, rice flour, sorghum flour and wheat flour formulations resulted in 37.00 to 61.00 per cent reduction of H. armigera. Least performance was observed by bajra flour formulation (34.33 per cent larval reduction).
Description
IDENTIFICATION OF POTENTIAL ISOLATES OF Nomuraea rileyi AND DEVELOPMENT OF FORMULATIONS
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