The availability and quality of nectar for adults are thought to affect fecundity of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Experiments were conducted to analyze the effect of adult feeding on the fecundity, and oviposition pattern of moths, and larval performance (egg hatch). The moths were fed either on distilled water, honey solution, or one of a range of concentrations of sucrose solution. The results showed that diets with sugars significantly increased fecundity and adult lifespan. Lifespan, total numbers of eggs and egg mass were significantly higher for females that fed on sugar during adult life. Egg hatch (a measure of offspring fitness) decreased over time regardless of sucrose concentration, but had always higher levels in the groups fed sugars. The peak of the ovipositing period was delayed and prolonged, with more eggs deposited, when moths were fed on sugar solution. In conclusion, adult feeding increases the fecundity of female moths and plays an important role in enhancing the fitness of individual cotton bollworm offspring.
The diapause inducement condition, cold hardiness, and flight ability in Cry1Ac-resistant (BtR) and Cry1Ac-susceptible (96S) strains of Helicoverpa armigera (Hübner) were compared in the laboratory. The BtR strain was derived from the 96S strain and shows 1375-fold resistance to the Cry1Ac toxin after having been selected for 52 generations. Compared with the 96S strain, the Bt-resistant strain was more likely to go into diapause under a short-photoperiod environment. At 11L : 13D, 12L : 12D and 13L : 11D photoperiods, the percentages of BtR insects entering diapause were 72.7%, 82.9% and 68.7%, respectively, which were significantly higher than those in the 96S strain (58.6%, 67.4% and 46.3%, respectively) under the same conditions. The supercooling points (SCP) and freezing points (FP) were not significantly different between the BtR and 96S strains. The LT50 (50% lethal time) and LT90 (90% lethal time) of BtR pupae were also not significantly different from those of the 96S strain at -15°C. The moths from both strains had similar flight ability when their larvae were fed with nontoxic control diet. However, the total flight distance of these BtR moths was 56.2 km whose larvae fed on normal diet, which was more than twice as much as for those feeding on Bt diet (26.2 km). Flight duration for these BtR moths was longer after feeding on normal diet (11.6 h) than after feeding on Bt diet (7.3 h).
Three secondary compounds, pyrocatechol, gramine and ferulic acid from wheat were separately incorporated into artificial diets and fed to cotton bollworm Helicoverpa armigera (Hübner) larvae to determine their effects on larval and pupal weights and the nutritional indices of the larvae. The results show that these three secondary compounds can decrease the mean larval and pupal weights of cotton bollworm, with the mean larvae weights differing significantly between treatments. Mean pupal weight was only significantly reduced by ferulic acid and gramine, but not pyrocatechol. There were significant correlations between mean larval weight and concentration of the three secondary compounds tested, and between mean pupal weight and concentration of ferulic acid and gramine. The three secondary compounds tested affected the nutritional indices of cotton bollworm larvae differently. Compared with the control, ferulic acid and gramine significantly decreased RGR (the relative growth rate), AD (approximate digestibility) and ECD (conversion efficiency) of cotton bollworm larvae, and pyrocatechol only reduced ECD. All three indices were the lowest for cotton bollworm larvae fed on the diet with gramine (0.0984 ± 0.0114 g/g/day, 14.2670 ± 1.1541% and 31.1337 ± 1.1213%).
In order to determine when during the development of H. armigera CYP6B6 is expressed, we measured the width of the head capsule, the length of the body and weight of the different life stages of the cotton bollworm reared under laboratory condition. The larvae took about 20 d to complete their development under these conditions, the pre-pupae about 4 d, pupae about 9 d, and the adults lived for about 9 d and the eggs took about 4 d to hatch. Knowing this it was possible to determine the pattern of cytochrome P450 CYP6B6 expression at different stages in the life cycle of H. armigera using real-time quantitative polymerase chain reaction (RT-qPCR). The CYP6B6 gene was expressed in all the developmental stages of the cotton bollworm. The results indicate that the level of expression was lower in the egg, pre-pupal, pupal and adult stages than in larvae. The level of expression of CYP6B6 decreased from the 1st to the 3rd instar larva, with the lowest level recorded in the 3rd instar larvae and then increased reaching its highest value in 6th instar larvae. A similar trend in the expression of CYP6B6 was detected using immunohistochemistry. As the results show, more efficient control of the cotton bollworm can be achieved if insecticides are applied when the larvae of H. armiger are in the 3rd instar, because at that stage the eat little food and there is a low level of detoxifying enzymes in the larvae., Xuetao Zhang ... [et al.]., and Obsahuje seznam literatury
A cDNA encoding aminopeptidase N3 was cloned by degenerated PCR and RACE techniques. The full-length of APN3harm is 3486bp. Open reading frame is 3042bp in length, encoding 1014 amino acid residues. Its predicted molecular weight and isoelectric point are 117.04 kDa and 5.14, respectively. This deduced amino acid sequence shares some common structural features with aminopeptidase N from Lepidoptera, including the consensus zinc-binding motif HEXXHX18E and the GAMEN motif common to gluzincin aminopeptidases. The full-length of the APN3harm gene from three susceptible and three resistant strains were cloned and sequenced. Comparison analysis revealed fourteen amino acid differences in the APN3harm gene from resistant and susceptible strains and six mutations of amino acids exist in all resistant strains. It is possible that these mutations are related to the resistance of Helicoverpa armigera to Cry1Ac toxin. The results of semi-quantitative RT-PCR showed that the resistance of H. armigera to Cry1Ac is unrelated to the amount of APN3harm mRNA in midgut tissue. In susceptible strains, APN3harm is highly expressed in mid-gut, foregut and hindgut but not in other tissues. To determine if the APN3harm is the receptor of Cry1Ac, recombinant APN3harm protein was successfully expressed in E. coli. A ligand binding experiment showed purified product could bind Cry1Ac toxin. So it is proposed that APN3harm is a putative receptor of Cry1Ac in H. armigera. The sequence of APN3harm was deposited in GenBank with the accession number AY052651.
The profile of hemolymph ecdysteroid was studied in the gram pod borer, Helicoverpa armigera, during larval-pupal transformation. The changes closely correspond to the developmental events occurring at metamorphosis. Two insect growth regulators, plumbagin and azadirachtin, significantly depleted the content and altered the profile of ecdysteroids at crucial stages, when applied at ED50 doses. The activity profiles of two fat body lysosomal enzymes, acid phosphatase and b-galactosidase, were also significantly affected by the insect growth regulators. It is suggested that plumbagin and azadirachtin treatments primarily modify the ecdysteroid titer, which in turn leads to changes in lysosomal enzyme activity causing overt morphological abnormalities during the metamorphic molt., Arulappan Josephrajkumar, Bhattiprolu Subrahmanyam, Srinivasan, and Lit