Morphological and Genetic Analysis of Four Color Morphs of Bean Leaf Beetle.

Bean leaf beetle (BLB), Cerotoma trifurcata (Forster; Coleoptera: Chrysomelidae), exhibits considerable color variation but little is known about the underlying genetic structure and gene flow among color phenotypes. Genetic and morphological variation among four color phenotypes-green with spots (G+S), green without spots (G-S), red with spots (R+S) and red without spots (R-S)-were analyzed using amplified fragment length polymorphisms (AFLP) and morphometrics, respectively. AFLP generated 175 markers that showed ≥80% polymorphism. Analysis of molecular variance (AMOVA) indicated that genetic variation was greatest within phenotypes (82.6-84.0%); gene flow among the four phenotypes was relatively high (Nm = 3.82). The dendrogram and STRUCTURE analysis indicated some population divergence of G-S from the other phenotypes. Morphological parameters were similar among phenotypes except that R+S showed significant differences in weight and body-length. Canonical variables 1 and 2, based on average morphometric characters, accounted for 98% of the total variation; some divergence was indicated between G+S and R+S from each other and from the G-S/R-S BLB color morphs. The pattern of genetic variation indicated potential divergence of G-S and G+S from each other and from R-S and R+S. Although these results indicate that the four different color morphs are not genetically or reproductively isolated, there is some genetic differentiation/structure and morphological dissimilarity suggesting weak/incomplete isolation.

Sequence-characterized amplified regions that differentiate New World screwworms from other potential wound-inhabiting flies.

New World screwworms, Cochliomyia hominivorax (Coquerel, 1858), were once devastating pests of warm-blooded animals in the United States before they were successfully eradicated using the sterile insect technique. Guarding against the introduction of screwworms to North America or any other screwworm-free area relies on rapid, reliable identification of suspected cases. In the current study, the DNA from excised markers generated by randomly amplified polymorphic DNA polymerase chain reaction was used as the basis to generate 2 species-specific sequence-characterized amplified region molecular markers. Resulting primer pairs, named CR92A1 and J1A2 (each with forward and reverse components), produced amplicons of 852 and 848 base pairs, respectively. The 2 primer pairs successfully discriminated between C. hominivorax, Cochliomyia macellaria (Fabricius, 1775), 8 other species of blowflies, 3 noncalliphorid dipterans, and 1 nondipteran outlier. These primers may become important tools for veterinary laboratories and the screwworm eradication and exclusion program for rapid identification or verification of suspicious larval samples in presumed outbreaks.

Population structure, genetic variability, and gene flow of the bean leaf beetle, Cerotoma trifurcata, in the Midwestern United States.

Bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is a common pest of soybean in the Midwest United States. However, there are currently no reports on the genetic variability of C. trifurcata. This study examined 15-30 individuals from 25 sample locations to estimate genetic variability and gene flow within and among C. trifurcata from across the Mid- west. Amplified fragment length polymorphism generated 175 markers for analyses. Results from analysis of molecular variance (AMOVA) indicated that the majority of genetic variation was from within samples; only a small amount of the total variation was attributed to the variation among the samples. The GST for the entire C. trifurcata population indicated that the majority of genetic variation was found within the samples, further supporting the AMOVA results. The estimated average gene flow among the C. trifurcata samples was 1.83. The Mantel test revealed no indication of correlation between geographical and genetic distance for all the C. trifurcata samples. These findings show that C. trifurcata in the Midwest are genetically heterogeneous and part of a large, interbreeding population.

Evaluation of buffalograss genotypes and full-sibs for chinch bug resistance.

Fifteen buffalograss, Buchloe dactyloides (Nutt.) Engelm, genotypes and 94 diploid full-sib progeny were evaluated for western chinch bug, Blissus occiduus Barber (Hemiptera: Lygaeidae), resistance in two separate studies. The experimental design for each study was a completely randomized design. Adult chinch bugs were introduced onto caged single clone genotypes and progeny in the greenhouse. Chinch bug damage was assessed using a 1-5 visual damage rating scale with 1 = < or = 10%; 2 = 11-30%; 3 = 31-50%; 4 = 51-70%; and 5 = > or = 70% of the buffalograss leaf area with severe discoloration, or dead tissue. Highly significant differences were found among the genotypes and progeny for chinch bug damage. Among the genotypes, Legacy, Prestige, 184, 196, Bowie, NE 3297, NE 2769, and NE 2768 were moderately resistant with damage ratings of > 1, but < 3, while NE 2990, NE 2838, and 1-57-19 were moderately susceptible with damage ratings of > or = 3, but < 4. Among the progeny, one progeny (MP45) was highly resistant with a chinch bug damage rating of 1.0, 78 progeny (83%) had moderate resistance, with damage ratings of > 1.0 and < 3.0, 13 progeny (14%) were moderately susceptible with damage ratings ranging from 3.0 to 3.9, while only two were highly susceptible with damage ratings of > or = 4.0. The significant variability among genotypes and progeny for chinch bug resistance indicates the ability to improve buffalograss resistance to chinch bugs through selection or hybridization of selected genotypes.

Growth and fitness components of wild x cultivated Sorghum bicolor (Poaceae) hybrids in Nebraska.

PREMISE OF THE STUDY: Gene flow from crops to wild relatives has received considerable attention since the advent of genetically modified crops. Numerous researchers have found wild-crop hybrids to be nearly as fit as their wild parents, which suggests that crop genes may persist in wild populations. Components of the ecological fitness of cultivated sorghum, its wild relative, shattercane, and their hybrids have not been studied. • METHODS: To assess the potential for gene introgression into shattercane, we crossed cultivated sorghum to a single inbred shattercane line to produce F(1) hybrids and measured growth and several components of ecological fitness in relation to both parents in Nebraska, USA. • KEY RESULTS: Germination of F(1) seeds was similar to that of its shattercane parent except at high temperatures, where it was as sensitive as the sorghum parent. The F(1) grew taller and produced more biomass than either parent, but the F(1) leaf area index was intermediate. Fecundity of the F(1) plant was similar to that of shattercane and much greater than that of cultivated sorghum. • CONCLUSIONS: Considering all data, the ecological fitness of shattercane × cultivated sorghum F(1) hybrids may be equivalent to the wild shattercane parent, which suggests that crop genes that are either neutral or beneficial to shattercane would persist in populations within agroecosystems.

Genetic variability of the european corn borer, Ostrinia nubilalis, suggests gene flow between populations in the Midwestern United States.

The European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), is a widely distributed and serious economic pest to corn production in the U.S. Genetic variability of O. nubilalis was studied in 18 sub-populations in the upper Midwestern United States using amplified fragment length polymorphism. The relatively low GST values indicate that more variation exists within populations than between populations. High gene flow (Nm) values were indicated across the entire O. nubilalis population; the lowest degree of gene flow was in the northern samples (Nm = 1.96) and the highest degree of gene flow was in the southern samples (Nm = 2.77). The differences observed in the respective regions (north vs. south) may be explained by the voltinism patterns (univoltine vs. multivoltine, respectively) of O. nubilalis: southern multivoltine populations have opportunities for multiple matings for the duration of the year, further mix alleles. AMOVA results also indicated that most of the genetic variation was within sub-populations ( approximately 81% of total variation); less variation ( approximately 13%) was detected among populations within each of the three regions as designated for this study. However, the most striking and unexpected result was the low percentage of variation between all groups ( approximately 6%), further supporting implications of a high degree of gene flow. These results provide support for current requirements of refugia corn planting in Bt-corn management. These results also indicate that if resistance to Bt were to evolve in O. nubilalis, quick action would be necessary to deter the rapid spread of the gene for resistance.

Population variation of the fall armyworm, Spodoptera frugiperda, in the Western Hemisphere.

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), the fall armyworm is the most economically important maize pest in the western hemisphere. This research focused on the genetic variability of the maize host strain because there is a lack of information in this area of S. frugiperda research. Amplified fragment length polymorphism (AFLP) was used to assess the genetic variability of S. frugiperda over a large geographic area. Twenty populations were collected from the maize, one population was collected from princess tree, one population was collected from lemon tree, and one population was collected from bermudagrass. The 23 populations were from Mexico, the continental United States, Puerto Rico, Brazil, and Argentina. The objective of this research was to evaluate whether the majority of genetic variability was within populations or between populations. The AFLP results showed that the majority of the genetic variability is within populations and not between populations, indicating minor gene flow and suggesting that S. frugiperda in the Western Hemisphere are an interbreeding population.

Increasing public understanding of transgenic crops through the World Wide Web.

Transgenic crops among the most controversial "science and society" issues of recent years. Because of the complex techniques involved in creating these crops and the polarized debate over their risks and beliefs, a critical need has arisen for accessible and balanced information on this technology. World Wide Web sites offer several advantages for disseminating information on a fast-changing technical topic, including their global accessibility; and their ability to update information frequently, incorporate multimedia formats, and link to networks of other sites. An alliance between two complementary web sites at Colorado State University and the University of Nebraska-Lincoln takes advantage of the web environment to help fill the need for public information on crop genetic engineering. This article describes the objectives and features of each site. Viewership data and other feedback have shown these web sites to be effective means of reaching public audiences on a complex scientific topic.