DURGA PRASAD, N. V. V. S.MARUTI, NADUVALAKERI2020-02-282020-02-282019http://krishikosh.egranth.ac.in/handle/1/5810143877D5913The studies on “Seasonal Incidence and Monitoring of Resistance Development in Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) on Bollguard II” were conducted at Regional Agricultural Research Station (RARS), Lam, Guntur during Kharif, 2018-19 with an aim to study the seasonal incidence, performance of popular BG II cotton hybrids of Andhra Pradesh against pink bollworm and monitoring of resistance development, growth and development of pink bollworm on Cry toxins i.e., Cry1Ac and Cry 2Ab. Seasonal incidence of pink bollworm was conducted in bulk plots with Jaadoo BG II cotton hybrid to assess the pink bollworm incidence at field level in correlation with weather factors under the controlled condition for sucking pests. In the study, the seasonal occurrence of pink bollworm by pheromone monitoring revealed that the catches of male moths of pink bollworm on cotton started from the month of August, crossed ETL (72.88 moths/trap/week) at 46th Standard week and the highest trap catch (1756.13 moths/trap/week) was observed during 4th week of January corresponding to 4th standard week. The correlation studies showed that pheromone trap catch was exhibited significant positive correlation and significant negative correlation with morning relative humidity and minimum temperature respectively. Regarding green boll damage, green boll locule damage and larval incidence was started from the month of November, the peak damage was recorded after three weeks of peak pheromone trap catches, with 95 % green boll damage, 59.3 % green boll locule damage and the larval incidence (33 larvae /20 bolls) was observed in 1st week February corresponding to 5th standard week i.e., 176 days after sowing. Weather parameters have influenced the pheromone trap catch to the extent of 44.95 per cent (R2=0.44), green boll damage up to 84.92 per cent (R2 =0.84), green boll locule damage up to 90.30 percent (R2=0.90) and incidence of pink bollworm larvae in cotton bolls to the extent of 91.40 per cent (R2=0.91) in transgenic BG II cotton. xv Filed investigation of the performance of popular BG II cotton hybrids of Andhra Pradesh against pink bollworm was assessed in an experiment with RBD design consisting of eight BG II hybrids viz., Jaadoo BG II, Raja BG II, Bhakti BG II, ATM BG II, Super B BG II, Neo BG II and RCH-659 BG II and one check with non-Bt cotton (NDLH-1938) during kharif, 2018-19. Field evaluation of different popular BG II cotton hybrids of Andhra Pradesh against pink bollworm indicated that there is no rosette flower up to the harvest, the incidence of pink bollworm in bolls was started at 110 days after sowing. The mean per cent damage in terms of green boll damage (27.14 %, 29.05 % and 30.95 %), green boll locule damage (10.92% 12.12% and 11.51%) and mean larval incidence (3.05 larvae / 10 bolls, 3.00 larvae / 10 bolls and 3.48 larvae / 10 bolls) was lower in Raja BG II, ATM BG II and Super BG II cotton hybrids compared to other test hybrids, but the highest incidence 50.95 % green boll damage, 26.26 % green locule damage and 7.70 larvae / 10 bolls were observed in control check i.e., non Bt cotton (NDLH-1938), however the same trend was continued in open boll damage and open locule damage at harvest respectively and Raja BG II, ATM BG II and Super BG II test hybrids were superior over all other test hybrids tested because of early termination nature of the hybrids which escaped from later season incidence when compared to other test hybrids. The experiment on monitoring of resistance development, growth and development of pink bollworm on Cry toxins was conducted in laboratory at RARS, Lam, Guntur, for which the pink bollworm populations were collected from Guntur, Prakasam, Krishna (Andhra Pradesh), Nalgonda (Telangana) in November and Raichur (Karnataka) in the month of September during 2018 and the collected population were reared to F1 generation on semi-synthetic diet and neonates were assayed with Cry toxins i.e., Cry1Ac and Cry2Ab. Resistance development in pink bollworm against Cry toxin in populations collected from different locations indicated that the Guntur district population showed a high level of resistance with an LC50 value of 3.621 µg ml-1 of Cry1Ac with a resistance ratio of 724.20 for Cry1Ac, but the lowest level of resistance was observed in Nalgonda district with LC50 value of 0.257 µg ml-1 of Cry1Ac with resistance ratio of 51.40 for Cry1Ac and again Guntur district population showed a high level of resistance with an LC50 value of 4.326 µg ml-1 of Cry2Ab with resistance ratio of 1442.00, but the lowest level of resistance was observed in Raichur district with LC50 value of 1.436 µg ml-1 of Cry2Ab with resistance ratio of 478.67 for Cry2Ab. Which indicate that BG II cotton which contain Cry1Ac + Cry 2Ab not able to control PBW because of resistance development. Growth and development of surviving pink bollworm larvae on Cry toxins under laboratory conditions revealed that larval period, larval weight, pupal weight, pupal period, per cent pupation and per cent adult emergence of pink bollworm showed that the effect of both toxins i.e., Cry1Ac and Cry2Ab at higher conc.(10 ppm in Cry1Ac and 5 ppm in Cry2Ab), lower conc. (0.01 ppm in both toxins) and untreated populations of respective districts were found narrow with marginal difference due to probable development of resistance to Cry toxins which was reflected in the field condition with huge population levels at fag end of the crop.en-USnullThesis