7,321 research outputs found
A RAPD-PCR-based genetic diversity analysis of Helicoverpa armigera and H. zea populations in Brazil.
No full textTherefore, the aim of this study was to determine the genetic diversity of H. armigera and H. zea populations by RAPD-PCR analysis. The most important result was the clustering of one H. armigera population in a group predominantly formed by H. zea. It could indicate a possible occurrence of an interspecific cross between these species. This is a concern to Brazilian agriculture due to the possibility of selection of hybrids well adapted to the American environment, which would be inherited from H. zea
Sucrose- and H+-dependent charge movements associated with the gating of sucrose transporter ZmSUT1
No full textBackground: In contrast to man the majority of higher plants use sucrose as mobile carbohydrate. Accordingly proton-driven sucrose transporters are crucial for cell-to-cell and long-distance distribution within the plant body. Generally very negative plant membrane potentials and the ability to accumulate sucrose quantities of more than 1 M document that plants must have evolved transporters with unique structural and functional features.
Methodology/Principal Findings: To unravel the functional properties of one specific high capacity plasma membrane sucrose transporter in detail, we expressed the sucrose/H+ co-transporter from maize ZmSUT1 in Xenopus oocytes. Application of sucrose in an acidic pH environment elicited inward proton currents. Interestingly the sucrose-dependent H+ transport was associated with a decrease in membrane capacitance (Cm). In addition to sucrose Cm was modulated by the membrane potential and external protons. In order to explore the molecular mechanism underlying these Cm changes, presteady-state currents (Ipre) of ZmSUT1 transport were analyzed. Decay of Ipre could be best fitted by double exponentials. When plotted against the voltage the charge Q, associated to Ipre, was dependent on sucrose and protons. The mathematical derivative of the charge Q versus voltage was well in line with the observed Cm changes. Based on these parameters a turnover rate of 500 molecules sucrose/s was calculated. In contrast to gating currents of voltage dependent-potassium channels the analysis of ZmSUT1-derived presteady-state currents in the absence of sucrose (I = Q/τ) was sufficient to predict ZmSUT1 transport-associated currents.
Conclusions: Taken together our results indicate that in the absence of sucrose, ‘trapped’ protons move back and forth between an outer and an inner site within the transmembrane domains of ZmSUT1. This movement of protons in the electric field of the membrane gives rise to the presteady-state currents and in turn to Cm changes. Upon application of external sucrose, protons can pass the membrane turning presteady-state into transport currents
Mortality of heliothis zea eggs : affected by predator species, oviposition sites, and rain and wind dislodgement
No full textTypescript (photocopy).Predation rates of Heliothis zea (Boddie) (Lepidoptera: Noctuidae) eggs located on cotton plants were determined by placing ����P labelled H. Zea eggs on different plant structures throughout the plants. Egg predation averaged 81.7, 81.4, and 57.7% during the summers of 1982, 1983, and 1984. Predation averaged 27.9% for sucking predators and 5.1% for chewing predators. Orius tristicolor (White), O. insidiosus (Say), Geocoris punctipes (Say), Pseudatomoscelis seriatus (Reuter), and Solenopsis invicta Buren contributed ca. 86% of the predation attributable to specific arthropods. A minor trend for predation over the three years was for slightly higher predation rates towards the tops of plants. Predation rates decreased each year as the season progressed from 81.8 to 100% in pre-squaring cotton, to 55 to 80% at first hard-boll stage. Egg dislodgement rates (EDR) increased with increasing time exposure to rain, wind, and rain plus wind, and increased for rain and rain plus wind as rain intensity increased. Rain dislodged eggs at the tops of plants and on leaf tops at higher frequencies than eggs lower on plants and on other plant structures. Wind dislodged more eggs towards bottoms of plants and on bolls. EDR after 60 min. exposure was 24 to 30% for rain (0.64 to 5.08 cm/h), 6 to 18% for wind (8.1 to 24.1 kph), and 34 to 48% for rain plus wind. Eggs placed on plants using moistened brushes had higher EDR than plants with moth-laid eggs. Dislodgement results were used to develop a model for H. zea egg mortality due to rain and wind. The model was used to estimate egg dislodgement by rain during field predation tests and can be used in making pest management decisions. Low recovery rates of radioactive Solenopsis invicta following placement of ����P labelled H. zea eggs on field cotton were investigated using laboratory colonies. Foragers that removed eggs from plants picked up more ����P than did workers sampled from colonies 12 to 72 h after egg introduction. Problems in finding labelled ants may be associated with low ����P levels per ant, together with difficulties locating and isolating labelled ants from the population
Influence of salicylic acid on phytochelatin synthesis in Zea mays during Cd stress
No full textAbstract: Presoaking maize (Zea mays) seeds in salicylic acid (SA) reduces damage caused by cadmium. In the present work the possible
role of phytochelatins (PCs) in SA-mediated protection against Cd toxicity was investigated. Seeds were presoaked in 0.5 mM SA, and
seedlings were grown in hydroponic solution containing 0, 0.01, 0.015, or 0.025 mM Cd. Treatment with Cd increased the PC levels in
maize roots, but only slight changes were observed in the leaves. Long-term exposure to Cd decreased the phytochelatin synthase (PCS)
activity in the roots and led to an increase in PCS and glutathione reductase (GR) activities in maize leaves. Although presoaking seeds
in SA solution before exposure to Cd may reduce the level of heavy metal injury and has an effect on the composition of individual PCs,
this protection is not directly connected with the altered regulation of PCs
Comparisons of assembled <i>H. zea</i> sequences to 15 known <i>H. zea</i> sequences.
No full texta<p>Published <i>H. zea</i> sequences available from NCBI GenBank were BLAST to the assembled sequences.</p>b<p>The completeness and accuracy of assembled sequences were assessed based on sequence identity and the alignment lengths.</p>c<p>The length of <i>H. zea</i> sequences from NCBI GenBank.</p
Natural control of Helicoverpa zea (Boddie) in Trans-Pecos cotton
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: p. 55-62.During the summers of 1996 and 1997 Helicoverpa zea aphics. (Boddie) life stages were monitored in insedicide-free cotton, Gossypium hirsutum L., in the Trans-pecos physiogeographic region of Texas. zea in each of the two vowing seasons. Partial ecological life tables were construed for H Total mortality (egg to 5th instar) approached 97% in both 1996 and 1997. The egg stage experienced the greatest amount of age-specific (qx) mortality in both years (82.5% in 1996 and 86.0% in 1997). Egg mortality was attributed to Trichogramma spp., Encarsia sp. ltr. artery Xercet), Orius tristicolor (White) and unexplained mortality. Unexplained mortality represented the largest portion of egg mortality (67.5% in 1996 and 65.4% in 1997). Third instars exhibited the highest age-specific mortality of the larval stages sampled in 1996 (67.2%) and 1997 (51.8%). No 6th instars were round in either year and 100% of the life stages sampled consisted of H. zea. Life stages monitored in 1996 and 1997 conformed to a Type III survivorship curve. Enzyme linked immunosorbent assay (ELISA) of field-collected 0. tristicolor revealed that adult and nymphal 0. tristicolor fed on H. zea eggs. No pattern was evident between the number of bookworm eggs consumed by 0. tristicolor in relation to the seasonal abundance of H. zea eggs. The consistency of the H. zea survivorship data from our study suggests that natural control of bookworm may be plausible in Trans-Pecos cotton without insecticidal intervention. Future studies should attempt to extrapolate this survivorship data on a larger scale to test whether bookworm populations are kept below economic thresholds without insecticidal intervention on an area-wide basis
Role of cotton trichome density and extrafloral nectar in bollworm (Lepidoptera : Noctuidae) egg parasitism and predation
No full textTypescript (photocopy).Field, greenhouse and laboratory studies were conducted to determine the effect of cotton trichome density on parasitism and predation of Heliothis zea (Boddie) eggs. In a no-choice field test of three cotton phenotypes differing in trichome density, parasitism of H. zea eggs by Trichogramma pretiosum Riley was 13-fold higher on the Smoothleaf cotton phenotype and 8-fold higher on the hirsute cotton compared to the Pilose cotton. In a free-choice field study comparing two cotton near-isolines, natural parasitism of H. zea eggs by Trichogramma spp. was 3-fold higher on the Smoothleaf phenotype compared to the Pilose phenotype. Further, no-choice greenhouse tests of Smoothleaf, hirsute and Pilose cottons demonstrated that predation of H. zea eggs by Chrysopa rufilabris (Burmeister) larvae improved as trichome density decreased. Laboratory studies showed that cotton leaf trichomes inhibited movement of T. pretiosum and C. rufilabris larvae over leaf surfaces. Thus, reduced trichome density on cotton improves the ability of T. pretiosum and C. rufilabris larvae to find and destroy H. zea eggs. Field, greenhouse and laboratory tests were conducted to determine the effect of nectariless cotton on parasitism and predation of H. zea eggs. Extrafloral nectar was essential to survival of T. pretiosum adults and thus accounted for greater parasitism of H. zea eggs on nectaried vs. nectariless cotton phenotypes. Further, the presence of extrafloral nectar did not adversely affect the functional response of C. rufilabris larvae to its prey, as there were equal number of H. zea eggs destroyed on the nectaried and nectariless cottons. Results from these studies demonstrate positive and negative interactions between host-plant resistance and biological control. The implications of these interactions for integrated pest management and the development of pest resistant cultivars are discussed
A comparative study of Tam3 and Ac transposition in transgenic tobacco and petunia plants
No full textTransposition of the Anthirrinum majus Tam3 element and the Zea mays Ac element has been monitored in petunia and tobacco plants. Plant vectors were constructed with the transposable elements cloned into the leader sequence of a marker gene. Agrobacterium tumefaciens-mediated leaf disc transformation was used to introduce the transposable element constructs into plant cells. In transgenic plants, excision of the transposable element restores gene expression and results in a clearly distinguishable phenotype. Based on restored expression of the hygromycin phosphotransferase II (HPTII) gene, we established that Tam3 excises in 30% of the transformed petunia plants and in 60% of the transformed tobacco plants. Ac excises from the HPTII gene with comparable frequencies (30%) in both plant species. When the β-glucuronidase (GUS) gene was used to detect transposition of Tam3, a significantly lower excision frequency (13%) was found in both plant species. It could be shown that deletion of parts of the transposable elements Tam3 and Ac, removing either one of the terminal inverted repeats (TIR) or part of the presumptive transposase coding region, abolished the excision from the marker genes. This demonstrates that excision of the transposable element Tam3 in heterologous plant species, as documented for the autonomous element Ac, also depends on both properties. Southern blot hybridization shows the expected excision pattern and the reintegration of Tam3 and Ac elements into the genome of tobacco plants.
Induction and regulation of detoxification enzymes in Heliothis zea (Boddie) by plant allelochemicals and insecticides
No full textTypescript (photocopy).The relationship between the diet of phytophagous insects and susceptibility to insecticides is complex. This dissertation attempted to shed light on several aspects of this relationship with Heliothis zea. The objectives were (i) to demonstrate in a lepidopterous herbivore the relationship between adaptation to host plant toxins and subsequent effects on susceptibility to insecticides, (ii) to elucidate the mechanism of adaptation to toxic chemicals at the cellular level, and (iii) to determine the role of insect developmental hormones in this adaptive process. Data were presented that suggest the major effect of dietary toxins in H. zea is the induction of selected detoxification enzymes. Aldrin epoxidase was induced in insects reared on different cotton cultivars. Only one cultivar, RDC-102, induced glutathione S-aryl transferase activity. The insects fed on fresh flower buds metabolized malathion and permethrin at much slower rates than the insects reared on artificial diets. The plant diets also altered the route of metabolism of permethrin. The plant toxins also inhibited insect growth and developmental rates, which complicated the understanding of the relationship between diet and insecticide susceptibility. The earlier larval instars were more susceptible to methyl parathion. However, when insects were reared on artificial diet with levels of plant allelochemicals not affecting growth rate, the larvae were more tolerant to methyl parathion, but there was no change in tolerance to permethrin. A receptor system similar to the Ah system that recognized polyaromatic hydrocarbons in mammals was shown to be present in H. zea. The ligand used was TCDD. Saturable, high affinity (K[subscript d] = 5.9nM, B[subscript max] = 0.5 pmoles/mg protein) binding of TCDD was measured in the fat body cytosol. Juvenile hormone was a strong competitor for the TCDD binding site(s). DDT and gossypol also competed for the site. TCDD showed JH-like activity by blocking pupation when insects were treated with 3.1 nmoles per insect. Four distinct microsomal proteins having similar M[subscript r] and pl values were induced by both TCDD and juvenile hormone. The competition for the TCDD binding sites by juvenile hormone I suggested this material was a natural ligand for the receptor protein. Saturable, high affinity binding (K[subscript d] = 5.56nM, B[subscript max] = 1.19 pmoles/mg protein) of juvenile hormone I was demonstrated in the fat body of late fifth instar H. zea larvae. The plant allelochemical myrcene also bound to the receptor with high avidity. Affinity for the juvenile hormone binding site was as follows: juvenile hormone I > juvenile hormone III > myrcene > methoprene >TCDD. This was the first example of competition for a high affinity juvenile hormone binding protein by a plant allelochemical. The significance of this research was that the juvenile hormone receptor in H. zea appeared to play a central role in the recognition and response to plant allelochemicals and also, to man made xenobiotics
Mode of inheritance and combining abilities for kernel row number, kernel number per row and grain yield in maize (Zea mays L.)
No full textBocanski J., Z. Sreckov, A. Nastasic, M. Ivanovic, I.Djalovic and M. Vukosavljev (2010): Mode of inheritance and combining abilities for kernel row number, kernel number per row and grain yield in maize (Zea mays L.) - Genetika, Vol 42, No. 1, 169- 176. Utilization of heterosis requires the study of combining abilities of potential parents. In view of this, the objective of this paper was to study combining abilities and determine the mode of inheritance and gene effects for the main agronomic character, grain yield, and its components, kernel row number and kernel number per row. Six inbred lines Were used in the study, three of which originated in the U.S., while the other three were developed at the Institute of Field and Vegetable Crops in Novi Sad. Kernel row number was inherited by superdominance, partial dominance, complete dominance and intermediacy. The mode of inheritance of kernel number per row and grain yield was superdominance. Additive gene action had the greatest influence on the expression of kernel row number, while the other two traits were influenced the most by nonalditive gene
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