Browsing by Author "Schroeder, Jill"

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    Meloidogyne aegracyperi n. sp. (Nematoda: Meloidogynidae), a root-knot nematode parasitizing yellow and purple nutsedge in New Mexico
    Eisenback, Jonathan D.; Holland, L. A.; Schroeder, Jill; Thomas, Steve H.; Beacham, Jacqueline M.; Hanson, S. F.; Paes-Takahashi, Vanessa; Vieira, Paulo (Society of Nematologists, 2019)
    Meloidogyne aegracyperi n. sp. is described from roots of purple nutsedge in southern New Mexico, USA. Mature females are small (310–460 μm), pearly white, with their egg masses completely contained inside root galls. The neck is often at a 90 to 130° angleto the protruding posterior end with the perineal pattern. The distance of the dorsal esophageal gland orifice (DGO) to the base of the stylet is relatively long (4.0–6.1 μm), and the excretory pore is level with the base of the stylet. The anterior portion of the rounded lumen lining of the metacorpus contains 3 to 10 small vesicles. The perineal pattern has a rounded dorsal arch with a tail terminal area that is smooth or marked with rope-like striae. Only two males were found. The body twists 90° throughout its length. The DGO to the base of the stylet is long (3.0–3.3) μm. The cephalic framework of the second-stage juvenile is weak, and the stylet is short (10.1–11.8 μm). The DGO to the base of the stylet is long (3–5 μm). The tail is very long (64–89 μm) and the hyaline portion of the tail is very narrow, making the tail finely pointed. Eggs are typical for the genus and vary in length (85.2–99.8 μm) and width (37.1–48.1 μm), having a L/W ratio of (2.1–2.6). Maximum likelihood phylogenetic analyses of the different molecular loci (partial 18S rRNA, D2-D3 of 28S rRNA, internal transcribed spacer (ITS) rRNA, cytochrome oxidase subunit II (COII)-16S rRNA of mitochondrial DNA gene fragments and partial Hsp90 gene) placed this nematode on an independent branch in between M. graminicola and M. naasi and a cluster of species containing M. chitwoodi. M. fallax, and M. minor. Greenhouse tests showed that yellow and purple nutsedge were the best hosts, but perennial ryegrass, wheat, bentgrass, and barley were also hosts.
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    Multi-Phase US Spread and Habitat Switching of a Post-Columbian Invasive, Sorghum halepense
    Sezen, U. Uzay; Barney, Jacob; Atwater, Daniel Z.; Pederson, Gary A.; Pederson, Jeffrey F.; Chandler, J. Mike; Cox, T. Stan; Cox, Sheila; Dotray, Peter; Kopec, David; Smith, Steven E.; Schroeder, Jill; Wright, Steven D.; Jiao, Yuannian; Kong, Wenqian; Goff, Valorie H.; Auckland, Susan; Rainville, Lisa K.; Pierce, Gary J.; Lemke, Cornelia; Compton, Rosana; Phillips, Christine; Kerr, Alexandra; Mettler, Matthew; Paterson, Andrew H. (PLOS, 2016-10-18)
    Johnsongrass (Sorghum halepense) is a striking example of a post-Columbian founder event. This natural experiment within ecological time-scales provides a unique opportunity for understanding patterns of continent-wide genetic diversity following range expansion. Microsatellite markers were used for population genetic analyses including leaf-optimized Neighbor-Joining tree, pairwise FST, mismatch analysis, principle coordinate analysis, Tajima’s D, Fu’s F and Bayesian clusterings of population structure. Evidence indicates two geographically distant introductions of divergent genotypes, which spread across much of the US in <200 years. Based on geophylogeny, gene flow patterns can be inferred to have involved five phases. Centers of genetic diversity have shifted from two introduction sites separated by ~2000 miles toward the middle of the range, consistent with admixture between genotypes from the respective introductions. Genotyping provides evidence for a ‘habitat switch’ from agricultural to non-agricultural systems and may contribute to both Johnsongrass ubiquity and aggressiveness. Despite lower and more structured diversity at the invasion front, Johnsongrass continues to advance northward into cooler and drier habitats. Association genetic approaches may permit identification of alleles contributing to the habitat switch or other traits important to weed/invasive management and/or crop improvement.