MOLECULAR CHARACTERISATION OF NATIVE Bt ISOLATES AND LABORATORY EVALUATION OF THEIR NANO-FORMULATIONS ON Helicoverpa armigera (Hub.)
Loading...
Date
2023-12-01
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Acharya N G Ranga Agricultural University
Abstract
The present study on “Molecular characterisation of native Bt isolates and laboratory evaluation of their nano-formulations on Helicoverpa armigera (Hub.)” was conducted at Department of Entomology, Agricultural College, Bapatla during the period 2021-22.
Molecular diversity studies of seven Bt isolates including a reference strain HD1 was done using 10 RAPD decamer primers (OPA-02, OPA-05, OPA-07, OPA-09, OPA-10, OPA-12, OPA-18, OPC-19, OPK-14 and OPN-05). All the primers showed polymorphism. The polymorphic information content of primers ranged from 00.388 (OPA-09) to 0.478 (OPA-12). The dendrogram constructed using NTSYSpc 2.02i revealed that the seven isolates fell into two different clusters comprising of three (Isolates 49, HD1 and 55) and four isolates (Isolates 16, 52, 493 and 51) respectively. PCoA constructed using PAST software revealed that isolate 16 and 52 showed close genetic relationship and also isolate 49 and HD1 were found to show close genetic relationship among themselves and higher divergence with the remaining isolates. Crystal protein profiling of Bt isolates done using SDS-PAGE revealed the presence of band at 130-140 kDa indicating presence of Cry1 protein in isolates-16 and HD1, Vip3 protein of 92kDa in isolate- 49 & 493 and Cry2 protein of 65-70 kDa in isolates- 51, 52 & 55 were observed.
To know the bioefficacy of native Bt isolates viz., isolate 16, 49, 51, 52, 55 and 493 along with a reference strain HD1 were grown on nano enriched media and bioassay was conducted on the third instar larvae of H. armigera. Mortalities were observed from 48h after treatment for isolates 16, 493 and HD1 and maximum mortality was observed after 72h of treatment. Mean per cent mortalities ranged from 21.67 to 96.67 for all the isolates with NPs. For Bt grown on CaO based nano enriched media, the mortalities ranged from 25 to 96.67% and for MgO and ZnO based nano enriched media, the mortalities ranged from 23.33 to 95% and 21.67 to 93.33%, respectively.
xvi
To confirm the insecticidal activity of seven native Bt isolates including a reference strain HD1, bioassay was conducted on the third instar larvae of H. armigera using diet incorporation method. Mean per cent mortality of native isolates ranged between 23.33 and 91.67 and the LC50 values were between 2.78 × 107 and 7.73 × 1011 CFU ml-1 and LT50 in the range of 104.62 to 140.57 hpi at a dose of 1× 1012. The highest mortality of 91.67 per cent was observed in HD1 with LC50 and LT50 values of 2.78 × 107 CFU ml-1 and 104.62 hpi, respectively. Among the native isolates the lethal action with reference to LT50 was recorded by isolate 493 followed by isolate I-16, I-51, I-49 and I-55 with 119.95, 130.78, 136.51 and 136.53 hpi respectively and the LC50 of 1.75×109, 1.09×1010, 2.90×1010 and 5.04×1010 respectively. LC90 values were in the range of 5.89 × 1011(HD1) to 5.75×1016(isolate- 52) and LT90 values were in the range of 162.47 hpi (HD1) to 245.93 hpi (isolate-55). Bioassay studies revealed that, the reference strain HD1 (96.67%) was more effective than the nanobased formulations of native isolates although, CaO based nano formulation of 493 (91.67%) was more effective among the native isolates.