Linkage disequilibrium in crosses between Illinois maize strains divergently selected for protein percentage

The objectives of this study were two fold: (1) to determine whether divergent selection for kernel protein concentration, which produced the Illinois high protein (IHP), Illinois low protein (ILP), reverse low protein (RLP), and reverse high protein (RHP) maize (Zea mays L.) strains, had generated coupling-phase linkages among genes controlling protein concentration or other traits and (2) to measure the effectiveness of random mating in reducing linkage disequilibrium in segregating generations from crosses between the strains. To achieve these objectives, design III progenies from the F₂ and F₆ (produced by random mating the F₂) from the crosses of IHP × ILP, IHP × RHP, ILP × RLP, and RHP × RLP were evaluated. Estimates of additive variance for percent protein in the crosses of IHP × ILP and ILP × RLP were significantly less in the F₆ than in the F₂ indicating the presence of coupling-phase linkages in the parents and their breakup by random mating. In addition, a significant reduction in dominance variance for grain yield from the F₂ to the F₆ in IHP × ILP suggested the presence of repulsion-phase linkages. No other evidence of coupling or repulsion-phase linkages was found for any of the traits measured. These results demonstrate the effectiveness of long-term divergent selection in the development of coupling-phase linkages and of random mating to dissipate linkage disequilibrium.Research supported by the Illinois Agricultural Experiment Station     

Mating-induced loss of sex pheromone and sexual receptivity in insects with emphasis on Helicoverpa zea and Lymantria dispar

Mating in most species of insects leads to a transient or permanent loss in sexual receptivity of the females. Among moths, this loss of receptivity is often accompanied with a loss of the sex pheromone in the absence of calling, which also could be temporary or permanent. Most of the earlier work on changes in reproductive behavior after mating was done with Diptera in which sperm and/or male accessory gland secretions were shown to be responsible for termination of receptivity. In the corn earworm moth, Helicoverpa zea, mated females become depleted of pheromone and become nonreceptive to further mating attempts, but only for the remainder of the night of mating. A pheromonostatic peptide isolated from the accessory glands of males may be responsible for the depletion of pheromone, while the termination of receptivity is independently controlled. In the gypsy moth, Lymantria dispar, the changes in behavior following mating are permanent. In this species, the switch from virgin to mated behavior involves three steps: a physical stimulation associated with mating, transfer of viable sperm to the spermatheca, and commencement of oviposition. Signals generated by these factors operate through neural pathways and, unlike in H. zea, accessory gland factors seem not to be involved. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Formulating Atoxigenic Aspergillus flavus for Field Release

A procedure was developed to encapsulate mycelia of an atoxigenic strain of Aspergillus flavus in alginate pellets for seeding into agricultural fields in order to reduce aflatoxin contamination via competitive exclusion. Kaolin, a clay filler commonly employed in alginate formulations, was detrimental to pellet performance as measured by spore yield. Corn cob grits, a by-product of the corn industry, was found to be an excellent replacement for kaolin. Of nine nutritive adjuvants tested, wheat gluten improved pellet performance the most, although gluten concentrations above 5% were difficult to process. The best formulation tested consisted of 1% sodium alginate, 5% corn cob grits and 5% wheat gluten. On a 'per gram' basis, this alginate formulation yielded more spores than either A. flavus sclerotia or colonized wheat seed. Pesticides were also tested as adjuvants with potential use for protecting pellets under field conditions. Only one (chloramphenicol) of four tested pesticides (the others were dichloran, rose Bengal and cyfluthrin) reduced pellet sporulation. Formulations with or without pesticide adjuvants retained similar spore yield potential during a 2-year storage at 8 C. However, spore production in stored products lagged behind that of fresh products. At 75% relative humidity (RH), pellet storage stability decreased with increasing temperature from 27 to 42 C. Pellet spore yield at 32 C decreased as RH decreased from 100 to 90%. Sporulation occurred at 90% RH but not at 88% RH. Spore yield varied widely in four field tests, and the cumulative spore yield was inversely correlated (r2= -0.798, P 0.01) with rainfall. The results suggest that alginate pellets may be effective formulations for delivery of atoxigenic A. flavus strains to furrow-irrigated cotton in desert environments, where aflatoxin contamination of cottonseed is most severe.     

Relationship of Heliothis zea predators, parasitoids and entomopathogens to canopy development in soybean as affected by Heterodera glycines and weeds

The influence of canopy development in soybean on the survival of corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), egg and larval stages and population dynamics of arthropod fauna were evaluated in field trials during 1986–88 in eastern North Carolina. Soybean canopy size decreased as soybean cyst nematode, Heterodera glycines Ichinohe (Nematoda: Heteroderidae), initial population densities increased. Plant species composition of the soybean canopy was affected by weed population densities. Mortality of H. zea larvae due to parasitism and infection with entomopathogens was greater in closed canopy and (or) weedy soybeans than in very open and (or) weed free soybeans. Predation and parasitism of corn earworm eggs were similar across nematode and weed density treatments. Natural enemy populations increased to highest levels during July in closed canopy and (or) weedy soybeans, coinciding with availability of largest prey population reservoirs. A delay in colonization of very open and (or) weed free soybeans by beneficial arthropods until mid to late August allowed greater H. zea larval survival than in closed canopy and (or) weedy soybeans. Arthropod species richness was generally greatest in closed canopy and (or) weedy soybeans during mid to late July, with differences becoming nonsignificant in August and early September. Mean and maximum ambient temperatures were higher and relative humidities lower in open canopy than in closed canopy plots. These conditions were less favorable for development of pathogens and natural enemies.     

Nutritional requirements for conidial germination and hyphal growth of Beauveria bassiana

Nutritional requirements for germination and growth of the entomopathogenic fungus Beauveria bassiana are not complex. For germination to occur, a utilizable source of carbon must be present; however, a nitrogen source is needed for continued hyphal growth, otherwise lysis ensues. Compounds that can serve as utilizable carbon-energy sources for germination include glucose, N-acetylglucosamine, glucosamine, chitin, starch, lanolin, hydrocarbons in crude oil, and some longer-chain fatty acids. Both organic and inorganic sources of nitrogen are readily utilized for growth. Conidia undergo active metabolism soon after being placed in a suitable growth medium, indicating that conidia are released from their state of dormancy several hours before emergence of the germ tube can be observed. Because of the nutritional versatility of B. bassiana, this fungus should be able to survive and be infective in several types of natural environments.     

Effect of zinc and phosphorus on the grain yield of corn (Zea mays L.) grown on a calcareous soil

Summary In a field experiment, more than 22% increase in the grain yield of corn was obtained by the application of 50 kg ZnSO₄/ha. Grain yields were also increased by increasing the level of applied phosphorus. Positive relationship was obtained between Zn and P, the phosphorus treatment increased Zn uptake by grains and vice versa.     

Vegetation maps based on remote sensing are informative predictors of habitat selection of grassland birds across a wetness gradient

Vegetation is a major environmental factor influencing habitat selection in bird species. High resolution mapping of vegetation cover is essential to model the distribution of populations and improve the management of breeding habitats. However, the task is challenging for grassland birds because microhabitat variations relevant at the territory scale cannot be measured continuously over large areas to delineate areas of higher suitability. Remote sensing may help to circumvent this problem. We addressed this issue by using SPOT 5 imagery and phytosociological data. We mapped grassland vegetation in a floodplain using two methods. We (i) mapped the continuous Ellenberg index of moisture and (ii) identified 5 vegetation classes distributed across the wetness gradient. These two methods produced consistent output maps, but they also provided complementary results. Ellenberg index is a valuable proxy for soil moisture while the class approach provided more information about vegetation structure, and possibly trophic resources. In spite of the apparent uniformity of meadows, our data show that birds do not settle randomly along the moisture and vegetation gradients. Overall birds tend to avoid the driest vegetation classes, i.e. the highest grounds. Thus, vegetation maps based on remote sensing could be valuable tools to study habitat selection and niche partition in grassland bird communities. It is also a valuable tool for conservation and habitat management.     

Complete green synthesis of silver-nanoparticles applying seed-borne Penicillium duclauxii

Seed-borne fungus Penicillium duclauxii was examined in this study to investigate its capability of synthesizing silver nanoparticles (Ag-NPs). In vitro experiments were conducted using corn-grain contaminating fungal isolate. Ag-NPs detection and characterization were assayed by the aid of spectroscopic techniques. Spectroscopy (energy dispersive), X-ray diffraction, transmission electron-microscope and optical absorption dimensions were employed.Ag-NPs with biosynthesized were used to test invitro against Bipolaris sorghicola; the cause of target leaf spot disease on sorghum plants. The myco-synthesis of Ag NPs using Penicillium duclauxii was proved in this study. Moreover, Bipolaris sorghicola was successfully inhibited by such Ag NPs in vitro.     

Effect of polyphenol extract on performance,serum biochemistry,skin pigmentation and carcass characteristics in broiler chickens fed with different cereal sources under hot-humid conditions

This study investigated the interaction between polyphenols with different cereal sources and their effects on performance, serum biochemistry, corticosterone levels and carcass characteristics in broiler chickens reared under hot-humid environment. Newly hatched coloured broiler chicks (n = 240) were randomly divided into six groups with five replicates of two different cereal sources, namely corn and broken rice-sorghum combined, and three levels of pomegranate peel polyphenol extracts (PPP) 0, 50 and 100 mg/kg in each cereal groups. Birds were maintained under standard management conditions for six weeks during hot-humid environment (Temperature: 29–36 °C; Relative Humidity: 69–80%). Fortnight body weight and feed consumption were recorded and serum biochemical constituents were estimated at 28 and 42 days of age. The body weight gain was significantly (p < 0.05) higher in broken rice-sorghum diet than in corn diet. The supplementation of polyphenols increased the skin and shank pigmentation. Serum protein, lipids and minerals showed significant difference due to cereals, polyphenols and their interactions. Corn-fed birds had significantly higher visceral organs weight than the alternate grain-fed broilers. The serum corticosterone levels were significantly reduced in the PPP supplemented groups than the control, it could be concluded that, supplementation of 50 mg/kg polyphenol extract from pomegranate peels improved production performance in broilers fed broken rice-sorghum as cereal source under hot-humid conditions.