Reduction In Larval Weight Research Articles

Growth Stimulant and Antifeedant Activity in Bermuda Grass Affecting the Fall Armyworm (Lepidoptera: Noctuidae)

Dietary nutrients were identified by mass spectroscopy from chromatographic isolates of the neutral lipid fraction of Bermuda grass, Cynodon dactylon L. (Pers.). These included methyl and ethyl linolenate, vitamin E (γ-tocopherol, α-tocopherol), and the 3 sterols: campestrol, stigmasterol, and sitosterol. Gas liquid capillary chromatographic analyses of these molecules indicated significant differences among the Bermuda grass genotypes, especially in sterol composition. Campestrol was present in most of the genotypes examined with stigmasterol and sitosterol, showing the greatest variability in abundance and occurrence among the Bermuda grass lines. Larvae of fall armyworm, Spodopterafrugiperda (J. E. Smith), fed on diet supplemented with the lipid fraction showed significantly higher larval weight accumulation (28-54%) compared with controls. Larval growth was variably dependent on the genotype or somaclone lipid profile. These findings confirm a major role for neutral lipids in insect growth physiology and, by implication, are key elements in Bermuda grass nutritive value. Additionally, an antifeedant also was isolated from Bermuda grass. A crude sohxlet extract from Bermuda grass (line OSU 71 X6-7) was sequentially fractionated by silica gel flash column and reverse-phase high-pressure'liquid chromatography (HPLC). A bioassay-guided scheme with the fall armyworm yielded an active antifeedant fraction eluting at 10% EtOAc/ CH 2 Cl 2 , from which a single active component was isolated by HPLC. The biological effects of these isolates on neonate fall armyworm larvae included a retardation of larval growth (80% reduction in larval weight) and an increase in duration to pupal metamorphosis (70%) that were significantly different from either control treatments or other chromatographic fractions. A concentration-dependent antifeedant response with the isolate to topically treated diet plugs was observed.

Novel Mechanism for Resistance to Colorado Potato Beetle (Coleoptera: Chrysomelidae) in Wild Solanum Species

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most destructive insect pest of the potato, Solanum tuberosum L., worldwide and has shown remarkable adaptability to insecticides. In wild Solanum species, the best known host-plant resistance mechanisms are a high level of foliar glycoalkaloids and the presence of specialized, glandular trichomes. Through a preliminary field-test screen, 3 Solanum species, Solanum trifidum, S. raphanifolium, and S. circaeifolium , were identified with low foliar glycoalkaloid levels and no glandular trichomes, but still exhibiting substantial resistance to L. decemlineata . These 3 species along with 2 species, S. berthaultii and S. chacoense, representing the 2 known mechanisms of resistance, were examined in bioassays for larval leaf consumption, effect on larval growth, and percentage of larval mortality. The best S. trifidum l accessions had 10-fold less foliar consumption per larva than controls and induced 54 % reduction in larval weight compared with controls during a 24-h feeding period. Forty-eight hour mortality rates were 100 % for 2nd and 3rd instars feeding on S. trifidum compared with 22 % for the S. tuberosum controls. Despite low foliar glycoalkaloid levels and the absence of glandular trichomes, S. trifulum accessions exhibited both an effective antinutritive and deterrent mechanism for resistance to L. decemlineata.

Expression of a Bacillus thuringiensis cryIA(c) gene in transgenic peanut plants and its efficacy against lesser cornstalk borer.

The invasion of peanut (Arachis hypogaea L.) pods and seeds by aflatoxin-forming species of Aspergillus is linked to injury by the lesser cornstalk borer and frequently causes a severe reduction in crop quality. The lesser cornstalk borer is susceptible to the lepidopteran-active Bacillus thuringiensis insecticidal crystal protein. We have introduced a codon-modified Bacillus thuringiensis cryIA(c) gene into peanut using microprojectile bombardment. The toxin-coding region of a Bt cryIA(c) gene was reconstructed for expression in plants and the resulting 3.4 kb gene cassette (promoter: 1.8 kb coding: 3') was directly cloned into the BglII site of plant transformation vectors. The vectors contained the hph gene, conferring resistance to the antibiotic hygromycin. Somatic embryos initiated from immature peanut cotyledons of two cultivars were used as the target for bombardment. DNA from hygromycin-resistant embryogenic cell lines, regenerated plants, and a progeny plant showed the presence and integration of hph and Bt genes by PCR and/or Southern blot analyses. ELISA immunoassay of the CryIA(c) protein from the hygromycin-selected plants showed the expression of CryIA(c) protein up to 0.18% of total soluble protein. Insect feeding bioassay of transformed plants indicated various levels of resistance to the lesser cornstalk borer, from complete larval mortality to a 66% reduction in larval weight. A negative correlation between percent survival or larval weight and the amount of Bt CryIA(c) protein was recorded indicating in general that the higher the protein level the lower the survival or larval weight of the insect. Based on leaf bioassay, transformation of peanut with vectors containing the Bt cryIA(c) gene may be effective in protecting the peanut plants from damage by lepidopteran insect larvae of lesser cornstalk borer.

Synergistic activity of a Bacillus thuringiensis delta-endotoxin and a bacterial endochitinase against Spodoptera littoralis larvae.

In an attempt to increase the insecticidal effect of the delta-endotoxin crystal protein CryIC on the relatively Cry-insensitive larvae of Spodoptera littoralis, a combination of CryIC and endochitinase was used. CryIC comprising the first 756 amino acids from Bacillus thuringiensis K26-21 and endochitinase ChiAII encoded by Serratia marcescens were separately produced in Escherichia coli carrying the genes in overexpression vectors. The endochitinase on its own, even at very low concentrations (0.1 microgram/ml), perforated the larval midgut peritrophic membrane. When applied together with low concentrations of CryIC, a synergistic toxic effect was obtained. In the absence of chitinase, about 20 micrograms of CryIC per ml was required to obtain maximal reduction in larval weight, while only 3.0 micrograms of CryIC per ml caused a similar toxic effect in the presence of endochitinase. Thus, a combination of the Cry protein and an endochitinase could result in effective insect control in transgenic systems in which the Cry protein is not expressed in a crystalline form.

Effects of population density and cadmium toxicity on growth and survival of blowflies

The blowfly Lucilia sericata has been reared on artificial diets containing from 0 to 200 mg Cd kg −1 at population densities ranging from 8 larvae per 4-g diet to 8 larvae per 32-g diet. Peak larval weight, development period, pupal weight, adult-emergence weight, and fecundity were measured. Larvae of blowflies respond to food deprivation by a reduction in larval weight and subsequent pupal and adult size. Contaminating the food supply with cadmium produced similar additive effects, reduced the growth rate, and increased the age of pupation. The results are of importance in determining the effects of environmental pollutants on population dynamics.

Vaccines against blowfly strike: The effect of adjuvant type on vaccine effectiveness

Vaccination of sheep with a partially purified extract of Lucilia cuprina larvae in some cases resulted in marked reduction of growth in larvae which fed on the sheep. Twelve adjuvants were assessed, in vitro and in vivo, to determine which induced the largest inhibitory effect on larval growth. The Freund's complete adjuvant and Quil A groups produced ELISA antibody levels significantly higher ( P<0.05) than other groups. Seven adjuvants mediated an immune response which caused significant inhibition of larval growth ( P<0.05). When the sheep were assessed by in vivo larval culture, only larvae feeding on sheep vaccinated with the antigen presented in Freund's complete adjuvant or dextran sulphate or a dextran sulphate/Freund's incomplete adjuvant mixture weighed significantly less ( P<0.05) than larvae feeding on control sheep. The effect on larvae was monitored in vitro for 70 days after vaccination, by which time significant reduction in larval weight was no longer observed. The loss of larval growth inhibition was not associated with a corresponding reduction in overall antibody levels.

Biochemical activity of centipedegrass against fall armyworm larvae

Centipedegrass,Eremochloa ophiuroides (Munro) Hack, severely inhibits growth of the fall armyworm larva,Spodoptera frugiperda (J.E. Smith). Fresh centipedegrass extracts and extract fractions were deposited on Celufil, incorporated into meridic-based diets and bioassayed against neonate larvae of the fall armyworm in the laboratory. The methanol extract (F1) caused the greatest reduction in larval weight. When F1, was partitioned between méthylene chloride and water, the activity was transferred to the water-soluble fraction (F5), which, when further fractionated using preparative C-18 reverse-phase chromatography, yielded active F7 and F8 fractions. Gas chromatograph-mass spectrometry and high-pressure liquid chromatography (HPLC) showed F7 to be 95% caffeoylquinic acids with chlorogenic acid as the major constituent. HPLC analysis of F8 revealed maysin [2″-O- α-L-rhamnosyl-6-C-(6-deoxy-Xylo-hexos-4-ulosyl)luteolin] and other luteolin derivatives. Chlorogenic acid and other caffeoylquinic acids, maysin, and other luteolin derivatives are the major factors responsible for the antibiotic resistance of centipedegrass to larvae of the fall armyworm.

Use of Glandless Breeding Stocks to Evaluate Unknown Heliothis Growth Inhibitors (X‐Factors) in Cotton1

A significant linear relationship (r = 0.86 to 0.90) was found between reduction in larval weight of tobacco budworm, Heliothis virescens (F•), and flowerbud gossypol content of 1) F3 progenies of Upland stocks crossed with three Texas race stocks (Texas 216, Texas 490, and Texas 1134) of cotton, Gossypium hirsutum L., and 2) 221 entries from the race stock collection. Most of the suppression of growth of larvae which fed on diets containing extracts of progenies from the three race stocks could be attributed to gossypol or to other compounds that occur in pigment glands and can be measured by the colorimetric method for gossypol involving reaction with aniline. Subsequently, 317 glandless progenies from glandless strains crossed with derivatives of Texas 27, Texas 194 and Texas 254 were assayed for their effect on larval growth. None of the glandless selections tested caused a reduction in larval growth compared with insects feeding on a casein‐wheat germ diet, which suggest that the X‐factor effect results from one of the following: 1) gossypol; 2) synergist or additive effects of gossypol and other toxic compounds in flowerbuds; 3) gossypol‐related compound that gives the same colorimetric test as gossypol but is more toxic than gossypol. Some of the glanded sister lines from the crosses suppressed larval weight by more than 50%, but generally this reduction was within the confidence limits of the reduction expected fxom gossypol content.

The Response of Larvae of the Large White Butterfly (Pieris brassicae (L.)) to Diets of Mineral-deficient Leaves

When larvae of Pieris brassicae (L.) were fed on leaves of plants showing symptoms of deficiency of nitrogen, phosphorus, potassium or iron, some or all of the following effects were recorded in each experiment: —Reduction of larval weight (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).Reduction of relative growth rate (deficiency of (1) N throughout larval life, (2) Fe from time of hatching, from sixth day and for last two larval instars).Increased larval mortality (deficiency of N, Fe from time of hatching).Delayed pupation (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).The more detailed experiments with iron-deficient diet showed that similar effects were produced at whatever stage of larval development it was first supplied.Larvae fed on iron-deficient leaves from the time of hatching appeared to have received a severe initial check to growth, but this was followed by some degree of recovery so that they showed a higher relative growth rate, a few days later, than larvae given the same diet six days after hatching.Preliminary trials were made on the effects of the addition to diets of iron-deficient leaves of various nutrient substances sprayed on to them. No markedly beneficial results were noted.