Browsing by Author "Harrison, Robert L."

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    Diallel analysis of rind puncture and grain yield and their interactions with plant densities for twelve elite inbred lines of maize, Zea mays L
    Perry, Christopher O. (Virginia Polytechnic Institute and State University, 1983)
    To better understand the genetics of stalk quality in elite Corn Belt germplasm, combining ability estimates for stalk quality as measured by rind puncture were obtained for twelve inbred lines of maize representing elite Corn Belt germplasm. Secondly, an attempt was made to assess the practical utility of the rind penetrometer as a tool to measure stalk quality in an applied maize breeding program. The twelve inbred lines of maize were crossed in a diallel manner to produce the 66 F₁ single cross hybrids. Hybrids were hand planted in single-row plots with three replications at Holland, Virginia on 10 April and 15 and 16 April, 1981 and 1982, respectively. Plots were comprised of four split-plots corresponding to planting densities of 39,536, 49,420, 59,304 and 69,188 plants per hectare. Rind puncture data were collected from five competitive plants in each density for each hybrid at midsi lk and two to three weeks later. Data were also collected on percent erect plants, stalk pinch values, and grain yield. Analyses of variance were performed on the means for each hybrid-density combination for all traits. Model I, Method 4 of Griffing (1956) was followed to obtain estimates of GCA and SCA effects. Highly significant differences were detected among hybrids and densities for rind puncture and grain yield in both years. Significant differences were also detected among hybrids for percent erect plants and stalk pinch value, although no significant difference among densities was evident. No significant difference was detected between dates of measurement for rind puncture. nents were highly significant for all GCA and SCA compotraits. Hybrid by density interaction was significant for grain yield and percent erect plants but not for rind puncture or stalk pinch. Hybrid by date interaction for rind puncture was highly significant in 1982 only. Considerable additive genetic variation associated with GCA was detected for rind strength as measured by rind puncture in elite Corn Belt germplasm. The rind penetrometer appears to be a useful tool to aid the breeder in identifying genotypes with superior rind strength, which in turn is a component of total stalk strength.
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    Field crop varieties for Virginia in 1981
    Harrison, Robert L. (Virginia Polytechnic Institute and State University. Extension Division, 1981-01)
    List of recommended crops for Virginians in 1981
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    Inheritance of reactions to gray leaf spot and maize dwarf mosaic virus in maize and their associations with physiological traits
    Donahue, Patrick J. (Virginia Polytechnic Institute and State University, 1989)
    Gray leaf spot, caused by Cercospora zeae-maydis, can be a yield-limiting factor in maize where continuous minimum tillage practices are followed. Commercial corn hybrids were evaluated for response to gray leaf spot for seven years at two Virginia locations (Shenandoah and Wythe Counties) and one year at a third location in Virginia (Montgomery County). Yield losses, when comparing resistant to susceptible classes, were approximately 2,000 kg ha⁻¹ at Wythe County in 1982, 750 kg ha⁻¹ at Shenandoah County in 1984, and 2,150 kg ha⁻¹ at Montgomery County in 1988. The inheritance of reaction to gray leaf spot was studied using a 14 inbred diallel in Montgomery and Wythe Counties, Virginia in 1987 and 1988 planted in randomized complete block designs. Resistance was found to be highly heritable and controlled by additive gene action. Inbreds producing high yielding, resistant, and agronomically superior hybrids were identified (B68, NC250, Pa875, Va14, Va17, and Va85); and several hybrids between these lines had high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875). Currently available inbreds could be used to produce hybrids with higher levels of resistance than hybrids currently available to growers, and these could serve as a basis for gray leaf spot breeding programs. Lesion size measurements were not correlated with disease scores. Late-season photosynthesis rates were associated positively with resistance. The hybrids of some inbreds were found to produce high levels of pigment (believed to be anthocyanins) around the gray leaf spot lesions. These did not limit the size of the individual lesion later in the season. Some pigment(s)-producing genotypes were found to be resistant when the pigment character was expressed. This type of resistance must prevent or inhibit infection of the leaf but not later colonization, once established. Maize dwarf mosaic virus (MDMV) also limits maize production in some areas where johnsongrass (Sorghum halepense L.) is a problem. Resistance to MDMV was found to be mainly additive and highly heritable. However, a strong specific combining ability component was found, indicating that the background of the material receiving resistance genes may have a strong effect on the expression of resistance. Inbreds capable of producing high-yielding, resistant, and agronomically acceptable hybrids are available (B68, NC250, A632, Pa875, Va17, and Va85); and several hybrids between these lines have high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875).
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    Transcriptomic resources for Bagrada hilaris (Burmeister), a widespread invasive pest of Brassicales
    Sparks, Michael E.; Nelson, David R.; Harrison, Robert L.; Larson, Nicholas R.; Kuhar, Daniel; Haber, Ariela I.; Heraghty, Sam D.; Rebholz, Zarley; Tholl, Dorothea; Grettenberger, Ian M.; Weber, Donald C.; Gundersen-Rindal, Dawn E. (Public Library of Science, 2024-12-27)
    The bagrada bug, Bagrada hilaris (Burmeister), is an emerging agricultural pest in the Americas, threatening agricultural production in the southwestern United States, Mexico and Chile, as well as in the Old World (including Africa, South Asia and, more recently, Mediterranean areas of Europe). Substantive transcriptomic sequence resources for this damaging species would be beneficial towards understanding its capacity for developing insecticide resistance, identifying viruses that may be present throughout its population and identifying genes differentially expressed across life stages that could be exploited for biomolecular pesticide formulations. This study establishes B. hilaris transcriptomic resources for eggs, 2nd and 4th larval instars, as well as male and female adults. Three gene families involved in xenobiotic detoxification—glutathione S-transferases, carboxylesterases and cytochrome P450 monooxygenases—were phylogenetically characterized. These data were also qualitatively compared with previously published results for two closely related pentatomid species—the brown marmorated stink bug, Halyomorpha halys (Stål), and the harlequin bug, Murgantia histrionica (Hahn)—to elucidate shared enzymatic components of terpene-based sex pheromone biosynthetic pathways. Lastly, the sequence data were screened for potential RNAi- and virus-related content and for genes implicated in insect growth and development.