Evolution of pest resistance threatens the benefits of genetically engineered crops that produce Bacillus thuringiensis (Bt) insecticidal proteins. Strategies intended to delay pest resistance are most effective when implemented proactively. Accordingly, researchers have selected for and analyzed resistance to Bt toxins in many laboratory strains of pests before resistance evolves in the field, but the utility of this approach depends on the largely untested assumption that laboratory- and field-selected resistance to Bt toxins are similar. Here we compared the genetic basis of resistance to Bt toxin Cry2Ab, which is widely deployed in transgenic crops, between laboratory- and field-selected populations of the pink bollworm (Pectinophora gossypiella), a global pest of cotton. We discovered that resistance to Cry2Ab is associated with mutations disrupting the same ATP-binding cassette transporter gene (PgABCA2) in a laboratory-selected strain from Arizona, USA, and in field-selected populations from India. The most common mutation, loss of exon 6 caused by alternative splicing, occurred in resistant larvae from both locations. Together with previous data, the results imply that mutations in the same gene confer Bt resistance in laboratory- and field-selected strains and suggest that focusing on ABCA2 genes may help to accelerate progress in monitoring and managing resistance to Cry2Ab.

Abstract:Field experiment was conducted at the Main Agricultural Research Station, University of Agricultural Sciences, Raichur during 2012-13 to identify and evaluate the suitable refuge strategy systems for pink bollworm resistance management in Bt cotton (Gossypium hirsutum L.) cultivation. The experiment was laid out in randomized complete block design with nine refuge systems : 0 % N-Bt (BIR), 5 % N-Bt (BIR), 10 % N-Bt (BIR), 15 % N-Bt (BIR), 20% N-Bt perimeter refuge, 100% Non Bt, 50% Non Bt, 10% structured refuge and 20% structured refuge as treatments with three replications in replacement series. Significantly lowest incidence (3.55 larvae/plant) and number of bolls with exit holes (11.22) due to pink bollworm was recorded in 0% BIR (41.25 q/ha) followed by 5 % N -Bt (BIR) with yield of 38.74 q/ha and this was on par with 10 % N-Bt (BIR) with yield of 37.79 is next best refuge systems with Bt cotton for higher production and greater economic benefits.

Banana germplasm with 17 different accessions for resistance were screened against banana stem weevil, Odoiporous longicollis in Koduru region of Kadapa district (Andhra Pradesh). All the accessions had infestation of stem weevil but with varying percent infestation. The 17 accessions of germplasm had weevil infestation ranging from 10.0-100 percent in 2012 with maximum infestation of 100 percent in red banana (AAA genome) followed by Bontha selection-88.88 % (ABB), Karpuravalli-84.60% (AAB) and Ellakibale-64.7% (AB) and the lowest was in Sugandhalu-10.00% (AAB). In the year 2013, the infestation was in the range of 13.00-90.40% and with respect to infestation levels in different accessions, and the trend remained same as the earlier year wherein the highest infestation was recorded in red banana-90.40% followed by Bontha selection with the damage of 83.50 %, Karpuravalli (79.80%), Ellakibale (70.00%) and least in Sugandhalu-13.0% (AAB). There was no correlation between number of adults observed and percent damage and similarly no relation can be drawn between percent infestation and height of oviposition, This implies that the infestation caused by the weevils varied in different genotypes and also this information will be further helpful in selecting the resistant germplasms for future.

Abstract:Whitefly species related to sunflower was identified as Bemisia tabaci (Gennadius). Further the identified whitefly species was confirmed to be indigenous B. tabaci on molecular basis by using B-biotype specific SCARs and biological silver leaf assay on sensitive pumpkin (cv Big variety). None of the whitefly samples could positive for the presence of B biotype. The results of the study on the pest life cycle under the laboratory conditions showed that, B. tabaci passed through four nymphal instars before the adult stage. The mean duration values of these stages were 5.6, 4.2, 4.4 and 5.6 days respectively. The total duration of the life cycle of B. tabaci ranged from 23-42 days at the temperature of 29±2°C with a mean of 34.5. The damage to sunflower crop caused by the whitefly species is discussed with a special emphasis on its ability to transmit leaf curl viral disease.

Seasonal incidence of major insect pests in groundnut was studied during kharif 2015-16 with the variety, Kadiri-6 (K6). The results indicated that the population of groundnut leaf miner (Aproaerema modicella) reached peak in the first week of September with a mean larval incidence of 0.8 plant-1 and the larval population of tobacco caterpillar (Spodopter alitura) was more abundant on the crop during second week of October with a mean incidence of 9.3 plant-1. Aphid (Aphis craccivora) touched the peak in the first week of September with a mean population of 8.8 aphids top 2 cm shoot-1; whereas, leaf hopper(Empoasca kerri) attained the peak in the second week of September with a mean population of 10.6 three leaves-1 plant-1. Maximum activity of thrips, Scirtothrips dorsalis (Hood) was recorded in the second week of October with a mean of 4.8 terminal-1. Leaf miner, leafhopper and aphids showed positive correlation with rainfall (r= 0.120, 0.158 and 0.121, respectively). In case of larval (r= -0.075) and adult (r= -0.103) populations of S. litura, adult catch of H. armigera (r= - 0.299) and thrips (r= -0.105) negative correlation were observed with rainfall. Larval and adult populations of S. litura and thrips showed positive correlation to both minimum (r=0.196, 0.159, 0.179) and maximum temperature (r=0.067, 0.266, 0.095, respectively). However, leaf miner, leafhopper, aphid populations and H. armigera adult catch showed negative correlation for maximum temperature (r= -0.008, -0.250, -0.014 and -0.148) and positive correlation with minimum temperature (r= 0.084, 0.663, 0.646 and 0.127, respectively). With respect to relative humidity, all the pest populations have showed negative correlation, however, leaf hopper and aphids only recorded significance at 5% with morning RH (r= -0.680 and -0.583). Peak activity of predators were recorded a week after the pest populations attained their peak.The populations of three predators’viz., coccinellids, spiders and syrphid fly maggots were positively correlated with all the pest populations