VTechWorks Repository :: Browsing by Author "Roane, Curtis W."

Browsing by Author "Roane, Curtis W."

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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.
A diallel study of flowering and of ear components of yield in Corn Belt maize and their interactions with population density
McClane, John Michael (Virginia Polytechnic Institute and State University, 1985)
A diallel study of American Corn Belt maize (Zea mays L.) was conducted at Holland, Virginia in 1981 and 1982. All possible crosses of twelve inbred parents (A619, A632, B73, H60, H93, H96, Mo17, Oh7B, Pa91, Val7, Va.79:419, Va85) were planted in three replications with population density treatments of 39,536, 49,420, 59,304, and 69,188 pl/ha in strips across hybrid treatments. Analyses of variance and combining ability analyses were performed on traits measuring the timing of anthesis (pollen shed) and silk emergence, on ear components of yield, and on components of kernel size. Density effects were highly significant for all traits, except for that of pollen shed duration, in the analyses combined over years. Hybrid-by-year interactions were highly significant for all traits. Correlations between GCA effects of grain yield and GCA effects of silking delay (anthesis-to-silking interval), kernels per row on the ear, ear kernel number, and kernel depth[(ear diameter - cob diameter)/2] were -0.79, 0.64, 0.66, and 0.80 in 1981, and 0.24, 0.81, 0.71, and 0.26 in 1982, respectively. Moisture stress sufficient to cause wilting occurred before and during silking in 1981. Apparently, short silking delay was associated with high moisture stress tolerance for grain yield in 1981 and was associated with long ear shoot length in 1982. Deep kernel depth apparently was associated with drought stress tolerance for yield as well. The heritabilities of ear traits were higher the earlier they became established in the sequence of development. Heritabilities of silking delay and most ear components of yield were increased by increasing planting density. However, the correlations among flowering and ear traits largely were unaffected by density, perhaps because densities were not high enough to make barrenness a substantial factor in grain yield. The most important traits related to yield were silking delay, kernels per row, kernel depth, and kernel row number. GCA to SCA variance component ratios were increased by combining data over years and by the more optimum season for yield.
Ecology of the stalk borer Papaipema nebris (Guenee), (Lepidoptera:noctuidae), in the southwestern Virginia no-till corn agroecosystem
Highland, H. Brett (Virginia Polytechnic Institute and State University, 1986)
The stalk borer (SB), Papaipema nebris Gn. exhibited from 7 to 9 instars when reared on a meridic diet in a control-led environment. Both sexes went through variable numbers of instars before pupation. Head capsule width measurements did not form discrete sets, and overlap occurred between adjacent instars. In feeding preference tests with first instar larvae using either leaf disks or stem sections, higher numbers of larvae fed on grasses, such as orchardgrass, Dactylis glomerata L. or fescue, Festuca arundinacea Schreb., compared to numbers feeding on other plants. In no-choice laboratory and field tests, larvae tunnelled into plant stalks at the same frequency by which they would feed on foliage, showing a tendency to tunnel into plants they accept as hosts. Third or fourth instar larvae preferred to tunnel into orchardgrass and rye, Secale cereale Lover the other plants present in field cage tests. The SB prefers to oviposit on narrow leaved, perennial grasses, such as fescue and orchardgrass, over wide leaved annual grasses or broadleaf plants. Significantly higher numbers of eggs were laid on upright over prostrate plants in cage studies. The SB also preferred ovipositing on desiccating or dry plant material. Higher numbers of SB infested corn seedlings were found next to field margins compared to numbers found within fields. Contour and transect maps of SB infested fields showed considerable aggregation over three years, and this distribution was confirmed by high variance to mean ratios, and small k values. SB distribution in no-till corn can be adequately described by the negative binomial model. Field collections of SB in corn stalks showed 2, 3, or 4 instar larvae infesting the youngest seedlings. Variation existed in larval development from year to year. Linear regression covariance analysis showed that larval development was different between field collected larvae from year to year.
Effect of dsRNA-containing and dsRNA-free hypovirulent isolates of Fusarium oxysporum on severity of Fusarium seedling disease of Essex soybean
Kilic, Ozlem III (Virginia Tech, 1997-08-07)
Sixty-six isolates of F. oxysporum and F. solani were recovered from healthy and necrotic Essex soybean seedlings grown in naturally infested soil. These were tested for pathogenicity at 20 C and -0.01 MPa water potential in artificially infested, autoclaved field soil. Highly pathogenic, moderately pathogenic, and hypovirulent isolates of both species were identified. Fifty-seven F. oxysporum and nine F. solani isolates were tested for the presence of dsRNA. The presence of dsRNA was not associated with hypovirulence in F. oxysporum since some hypovirulent isolates contained dsRNA while other hypovirulent isolates did not. Furthermore, of six dsRNA-containing F. oxysporum isolates, three were hypovirulent, two were moderately pathogenic, and one isolate was highly pathogenic. Four segments of dsRNA, with sizes of 4.0, 3.1, 2.7, and 2.2 kb, were detected in extracts of all six F. oxysporum isolates. No morphological differences were found between dsRNA-containing and dsRNA-free F. oxysporum isolates. Attempts to cure dsRNA-containing hypovirulent F. oxysporum isolates, either by single-sporing of isolates or by using a range of concentrations of cycloheximide, were not successful. No dsRNA was found in any of the F. solani isolates tested. Pythium ultimum, an associate in Essex seedling disease, was isolated from water-soaked lesions and interfered with evaluations of disease caused by the Fusarium spp. Metalaxyl was used to control P. ultimum and had no apparent effect on symptoms associated with F. oxysporum and F. solani in field soil. Prior inoculation of Essex soybean seeds with conidia of dsRNA-free hypovirulent F. oxysporum isolates, plus metalaxyl seed treatment, significantly (p<0.05) reduced disease severity on both cotyledons and hypocotyls and increased the rate of seedling emergence in field soil, compared to the control plants treated with metalaxyl alone or not treated with metalaxyl. No significant (p>0.05) differences were found between dsRNA-containing and dsRNA-free hypovirulent F. oxysporum isolates in their effects on the reduction of disease severity. A mixture of two hypovirulent F. oxysporum isolates was significantly (p<0.05) more effective than single hypovirulent F. oxysporum isolates in increasing the rate of seedling emergence. Symptoms associated with P. ultimum were not affected by the prior inoculation of seeds with individual hypovirulent F. oxysporum isolates.
Genetic analysis of soybean reactions to soybean mosaic virus
Ma, Guorong (Virginia Tech, 1995-09-05)
The soybean [Glycine max (L.) Merr.] mosaic disease, caused by soybean mosaic virus (SMV), is one of the most important soybean diseases in many areas of the world. This research, conducted in four separate studies, was designed to identify and characterize new sources of genes for resistance to SMV and to investigate the interaction of soybean resistance genes and SMV strains.
Genetics of reactions to soybean mosaic virus in soybean
Chen, Pengyin (Virginia Polytechnic Institute and State University, 1989)
The genetic interactions among 9 soybean [Glycine max (L.) Merr.] cultivars and 6 strains of soybean mosaic virus (SMV) were investigated. The objectives were to identify genes and/or alleles conditioning resistant and necrotic reactions to SMV and to determine the genetic relationships among resistance genes from cultivars exhibiting differential responses to the SMV strains. Seven SMV-resistant (R) cultivars (‘PI 486355’, ‘Suweon 97’, ‘PI 96983’, ‘Ogden’, ‘York’, ‘Marshall’, and ‘Kwanggyo’) were crossed in all combinations among each other and with susceptible (S) cultivars ‘Essex’ and ‘Lee 68’. F₂ populations and F₂-derived F₃ lines were inoculated in field with the SMV type strain Gl and in the greenhouse with the virulent strains G4, G5, G6, G7, and G7A. All F₂ populations from R x S and necrotic (N) x S crosses having PI 96983, Ogden, York, Marshall, and Kwanggyo as either resistant or necrotic parents segregated 3R:1S and 3N:1S, respectively. F₂-derived F₃ progenies from R x S crosses exhibited an F₂ genotypic ratio of 1 homogeneous R : 2 segregating (3R:1S) : l homogeneous S. The results indicate that each of these five resistant parents has a single, dominant or partially dominant gene conditioning the resistant and necrotic reactions to SMV. No segregation for SMV reaction was evident in F₂ and F₃ generations from R x R, N x N, and S x S crosses among the five differential cultivars, indicating that the resistance genes in the five cultivars are alleles at a common locus. The alleles in PI 96983 and Ogden were previously labeled Rsy and rsy^t, respectively. Gene symbols, Rsy^y, Rsy^m, and Rsy^k are proposed for the resistance genes in York, Marshall, and Kwanggyo, respectively. It is also proposed that the gene symbol rsy^t be changed to Rsy^t to more accurately reflect its genetic relationship to the susceptible allele. The R x S crosses with PI 486355 and Suweon 97 as resistant parents segregated 15R:1S in the F₂ and 7 (all R) : 4 (3R:1S) : 4 (15R:1S) : 1 (all S) in the F₃, indicating that each has two independent genes for resistance to SMV. The F₂ plants of PI 486355 x Suweon 97 showed no segregation for SMV reaction, suggesting that they have at least one gene in common. The crosses among all 7 resistant parents produced no susceptible segregates when inoculated with strain G1. It is concluded that the 7 resistant cultivars each have a gene or allele at the Rsy locus. Data from the experiments furnished conclusive evidence that the necrotic reaction in segregating populations is highly associated with plants that are heterozygous for the resistance gene.
A History of Plant Pathology in Virginia (1888-1997)
Roane, Curtis W. (University Archives, Virginia Tech, 2003-04)
Introduction The Pre-Alwood Era The Alwood Era (1888-1904) The Moncure Era (1904-1908) The Reed Era (1908-1915) The Fromme Era (1915-1928) The Wingard Era (1928-1964) I - 1928-1935 II - 1935-1949 III - 1949-1964 The Couch Era (1965-1974) The Foy Era (1974-1980) The Hooper Era (1980-1984) The Moore Era (1984-1997)
Inheritance of resistance to Rhynchosporium secalis (Oud.) J.J. Davis in Barley
Chi, Kuo-Ruey (Virginia Tech, 1961-05-26)
Thirty-two resistant varieties of winter type barley from the United States Department of Agriculture's World Collection were chosen for a study of the inheritance of scald resistance. They were crossed with Wong (0.1. 6728), a highly susceptible variety and with Hudson (0.I. 8067), a highly resistant variety. The crosses with Wong were made for the purpose of determining the number of pairs of genes for resistance in each of the resistant varieties. The crosses with Hudson were made for the purpose of determining whether any of the resistant varieties has genes for scald resistance at loci other than in Hudson. The F2 seedling populations from these crosses were studied in the greenhouse at Blacksburg in the early spring of 1960 and the winter of 1961.
Location of genes conditiioning resistance of barley to leaf rust (Puccinia hordei Otth)
Larkins, James Russell (Virginia Polytechnic Institute and State University, 1982)
Conventional linkage and primary trisomic analyses were undertaken to locate genes conditioning resistance of barley (Hordeum vulgare L.) to Puccinia hordei Otth. The linkage relationships of resistance genes Pa in Speciale (C.I. 7536) and Pa₇ in Cebada Capa (C.I. 6193) with genes known to reside on chromosomes 2 and 3 were studied in crosses involving Speciale and three chromosome 2 markers (e, gs₅, and lr), and in crosses involving Cebada Capa and four chromosome 3 markers (gs₂, uz, als, and yst₂). The location of the resistance gene Pa₃ in Estate was studied by primary trisomic analysis. Inheritance of leaf rust resistance was determined by seedling reaction to culture 57-19, race UN4 of Puccinia hordei. The inheritance and linkage relationships of marker genes and rust resistance were analyzed from F₂ and F₃ coupling data. A recombination value of 41.0 ± 2.2% was found between Pa and gs₅, a marker for chromosome 2L. No evidence was obtained linking Pa with genes e or lr, but population sizes were too small to detect reliably loose linkages in these populations. A loose association was observed between Pa₇ and yst₂ a marker for chromosome 3S; however, the data were not sufficiently homogeneous to permit estimation of a recombination value. The data from crosses involving Pa₇ and uz were not consistent but one population exhibited a trend which suggested these genes might be linked. No evidence of linkage was observed in crosses between Pa₇ and the genes gs₂ and als, although population sizes were limited. The assignment of Pa₇ to chromosome 3 was confirmed by primary trisomic analyses. By the same method, the Pa₃ gene in Estate was shown to be independent of chromosome 3. High temperatures during leaf rust inoculation and incubation periods resulted in poor expression of infection type in crosses involving Estate and Triplo 4, 5, and 6. Despite this the data from these crosses indicated that Pa₃ is not likely inherited through chromosomes 4 through 6. Accrued data suggest that Pa₃ may be located on chromosome 1.
Maize dwarf mosaic virus: purification, some physical properties, and yield of virus from several corn hybrids
Jones, Ronald K. (Virginia Tech, 1971-04-05)
To better understand the nature of maize dwarf mosaic virus (MDMV) and its interaction with susceptible and resistant corn hybrids, the purification of MDMV and its physical properties were re-evaluated and a rapid assay procedure was developed. The virus was purified by chloroform clarification and differential and sucrose density-gradient centrifugation. Corn tissue was homogenized in 0.1 M sodium citrate plus 0.5% mercaptoethanol. The virus was resuspended after high speed centrifugation in 0.005 M sodium citrate, pH 7.0. Purified virus has an ultraviolet absorption spectrum typical for filamentous viruses having 5% RNA, shows birefringence, has an A260/280 of 1.18, and a sedimentation coefficient of 160-162 S. The virus is filamentous and appears to be a member of the potato virus Y group. A yield of 9.0-23.0 llg of virus/g fresh weigh.t of field-grown, mechanically inoculated Hy X Cl03 was determined by analytical sucrose density-gradient centrifugation. This represents a yield of purified virus of approximately 25% of that in the clarified sap. Results obtained from the density-gradient analysis were comparable to but more sensitive than those from the microprecipitin test and a systemic infectivity assay. The systemic infectivity assay on corn, analyzed by maximum likelihood and log log transformation, showed a yield of purified virus of 0.4% of that in the crude sap.
Roland Jay Stipes
Roane, Curtis W. (Virginia Tech, 2003)
An overview of the career of Roland Stipes, Professor of Plant Pathology at Virginia Tech, including graduate student advisees and an extensive publications list.

Browsing by Author "Roane, Curtis W."

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