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Studies on the ringspot disease of crucifers and its incitant Mycosphaerella brassicicola (Fr.) LindauNelson, Merritt Richard, January 1958 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 19 (1958) no. 4, p. 627. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [60]-63).
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Nutritional Requirements of Corynebacterium poinsettiaeHooshdaran, Farideh 12 1900 (has links)
In a minimal medium supplemented with glucose and yeast extract, the optimum pH for the growth of C. poinsettias was found to be 7.5. The organism requires thiamine, biotin, and pantothenic acid for growth. No absolute requirement was found for any amino acid, purine or pyrimidine although an amino acid mixture was stimulatory. Casamino acids could be substituted for the synthetic amino acid mixture. Yeast extract provided an additional factor(s) necessary for maximal growth. The results suggest that the unknown factor found in yeast extract might be purified by a combination of solvent extraction, and adsorption and elution from charcoal.
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Gray leaf spot of corn: yield loss and evaluation of germplasm for resistanceCarter, Michele R. 06 October 2009 (has links)
Gray leaf spot (GLS) of corn (Zea mays L.), caused by the fungus Cercospora zeaemaydis (CZM) (Tehon and Daniels) has increased in incidence and severity with increasing use of no-tillage and continuous corn practices. This disease can be yield limiting. Corn hybrids were evaluated under natural disease pressure for three years (1989, 90, and 91) at two locations (Montgomery and Wythe Co., VA). Yield losses ranged from 2127.4 kg/ha (Wythe Co., 1991) to 4242.2 kg/ha (Wythe Co., 1990). It was estimated that 77% of the variability in yield was due to GLS. Fungicides were evaluated for the control of GLS over three years on a susceptible hybrid, Pioneer Brand 3320. All fungicides, with the exception of mancozeb, provided significant control over nontreated check in all years. Benomyl, propiconazole and terbutrazole were the most effective fungicides. As much as 93% of the variablilty in yield was attributed to blighting. Reduction in blighting also increased the kernel weight. The toxin, cercosporin, produced by CZM was evaluated for its ability to elicit differential responses in corn germplasm by three methods, ie., vein inoculation, root, and shoot uptake. No consistant differential reponses were found with vein inoculation, but 31-day old plants were significantly more sensitive to the toxin than 21-day old plants, as measured by lesion width. Root and shoot uptake of the toxin by inbred germplasm produced lesions that resembled those produced by CZM in the field. Microscopic, yellow fluorescing crystals were found associated with necrotic tissue from toxin-treated inbreds. Significantly more injury occurred to toxin-treated inbreds exposed to light than to darkness. By chromatographic analysis, 407.1-1076.7 ng of toxin/g of tissue was recovered from leaf lesion extracts of plants exposed to light. Five inbreds (B73, H99, Va59, NC250a, and NC264) showed consistent and differential responses to the toxin. H99 and NC250a showed differential responses to the same concentration of toxin, thus suggesting that some germplasm are more sensitive to the toxin than others. Tests using the toxin as a means to identify resistant germplasm did not provide reliable predictions of germplasm response to CZM in the field. / Master of Science
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Correlation of early leafspot disease in peanut with a weather- dependent infection indexJewell, Elspeth Lea January 1987 (has links)
Development of early leafspot, caused by Cercospora arachidicola Hori, was monitored on' Florigiant' peanut (Arachis hypogaea L.) at two field sites in Suffolk, Virginia. In one study, plants in 27-cm-diameter plots were inoculated with 20,000 conidia and inoculation dates were replicated in five randomized complete blocks. At location one in 1985 and 1986, lesions/leaf at two weeks after inoculation correlated significantly (P ≤ 0.05) with infection indices (IND) developed by the Virginia leafs pot advisory and hours of relative humidity (RH) ≥ 95%. At location two, correlations between lesions/leaf and IND as well as hours of RH ≥ 95% were significant in 1986, but not in 1985. Certain site specific factors were believed to have altered plant susceptibility to leafspot at this site in 1985. In another study, pots with greenhouse-grown peanut were placed between unsprayed rows of field plants, heavily colonized by C. arachidicola. Plants were removed after 3, 5, and 7 days of field exposure for six consecutive weeks in 1986 and returned to the greenhouse. Lesions/leaf at two weeks after initial exposure were correlated with IND values computed by five versions of the leaf spot advisory. Significant correlations were found between lesions/leaf on plants with field exposures of 5 and 7 days and cumulative IND values and hours of RH ≥ 90% and 95%. The low incidence of lesions resulting with field exposures of only 3 days coupled with a lack of significant correlations between disease and cumulative IND values for 3 days after inoculation in both studies suggests that infection processes require several days, and that fungicides may be applied to achieve disease control during this time. / M.S.
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Genetic mapping of gray leaf spot resistance genes in maizeLehmensiek, Anke 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Gray leaf spot (GLS) of maize, caused by the fungus Cercospora zeae-maydis,
can reduce grain yields by up to 60% and it is now recognized as one of the most
significant yield-limiting diseases of maize in many parts of the world. The most
sustainable and long-term management strategy for GLS will rely heavily on the
development of high-yielding, locally adapted GLS resistant hybrids.
Molecular markers could be useful to plant breeders to indirectly select for genes
affecting GLS resistance and to identify resistance genes without inoculation and
at an early stage of plant development. Only two studies in the USA have
examined quantitative trait loci (QTL) association with GLS resistance.
The aim of this study was to map GLS resistance genes in a resistant Seed Co
LTD, Zimbabwean inbred line. Molecular markers linked to the GLS resistance
QTL were identified by using the amplified fragment length polymorphism (AFLP)
technique together with bulked segregant analysis. Eleven polymorphic AFLP
fragments were identified and converted to sequence-specific PCR (polymerase
chain reaction) markers. Eight of the 11 converted AFLP markers were added to
the maize marker database of the University of Stellenbosch.
Five of the 8 converted AFLP markers were polymorphic between the resistant
and the susceptible parent. They were amplified on the DNA of 230 plants of a
segregating F2 population and linkage analysis was performed with
MAPMAKER/EXP. Two linkage groups consisting of two markers each, with a
linkage distance of 10.4 cM (LOD 22.83) and 8.2 cM (LOD 55.41) between the
two markers, were identified. QTL mapping with MAPMAKER/QTL confirmed the
presence of QTL in both linkage groups. Two publicly available recombinant inbred families (Burr et a/., 1988) were used
to localize the converted AFLP markers on the genetic map of maize. The QTL,
which were identified with the AFLP markers, were mapped to chromosomes 1
and 5. Another AFLP marker was mapped to chromosome 2 and a further to
chromosome 3.
To obtain more precise localizations of the QTL on chromosomes 1 and 5,
sequence-tagged site markers and microsatellite markers were used. The
markers were amplified on the DNA of the 230 plants of the F2 population and
linkage analysis was performed with MAPMAKER/EXP. The order of the markers
was in agreement with the UMC map of the Maize Genome Database. Interval
mapping using MAPMAKERlQTL and composite interval mapping using QTL
Cartographer were performed. The QTL on chromosome 1 had a LOD score of
21 and was localized in bin 1.05/06. A variance of 37% was explained by the
QTL. Two peaks were visible for the QTL on chromosome 5, one was localized in
bin 5.03/04 and the other in bin 5.05/06. Both peaks had a LOD score of 5 and
11% of the variance was explained by the QTL.
To test the consistency of the detected QTL, the markers flanking each QTL
were amplified on selected plants of two F2 populations planted in consecutive
years and regression analysis was performed. Both the QTL on chromosome 1
and the QTL on chromosome 5 were detected in these populations. Furthermore,
the presence of a QTL on chromosome 3 was confirmed with these populations.
A variance of 8 -10% was explained by the QTL on chromosome 3.
In this study, a major GLS resistance QTL was thus mapped on chromosomes 1
and two minor GLS resistance QTL were mapped on chromosomes 3 and 5
using a resistant Seed Co LTD, Zimbabwean inbred line. Markers were identified
which could be used in a marker-assisted selection program to select for the GLS
resistance QTL. / AFRIKAANSE OPSOMMING: Grys blaarvlek (GBV) van mielies, veroorsaak deur die swam Cercospora zeaemaydis,
kan graanopbrengs met tot 60% verlaag en word beskou as een van die
vernaamste opbrengs-beperkende siektes wêreldwyd. Die toepaslikste
langtermyn stragtegie vir GBV beheer sal wees om plaaslike mieliebasters met
hoë opbrengs en GBV weerstand te ontwikkel.
Molekulêre merkers kan nuttig deur plantetelers gebruik word om
weerstandsgene te selekteer. Seleksie is moontlik in die afwesigheid van
inokolum en op 'n vroeë stadium van plant ontwikkeling. Slegs twee vorige
studies (in die VSA) het kwantitatiewe-kenmerk-Iokusse (KKL), vir GBVweerstand
ondersoek.
Die doel van hierdie studie was om die GBV weerstandsgene in 'n
weerstandbiedende ingeteelde lyn (Seed Co BPK, Zimbabwe) te karteer.
Molekulêre merkers gekoppel aan die GBV weerstands KKL is geïdentifiseer
deur gebruik te maak van die geamplifiseerde-fragmentlengte-polimorfisme-
(AFLP-) tegniek en gebulkte-segregaat-analise. Elf polimorfiese merkers is
geïdentifiseer en omgeskakel na volgorde-spesifieke PKR (polimerase
kettingreaksie) merkers. Agt van die elf omgeskakelde AFLP-merkers is by die
mieliemerker databasis van die Universiteit van Stellenbosch gevoeg.
Vyf van die 8 omgeskakelde AFLP-merkers was polimorfies tussen die bestande
en vatbare ouers. Hulle is geamplifiseer op die DNA van 230 plante van 'n
segregerende F2-populasie en is gebruik in 'n koppelingstudie met
MAPMAKER/EXP. Twee koppelingsgroepe, elk bestaande uit twee merkers, met
onderskeidelik koppelingsafstande van 10.4 eM (LOD 22.83) en 8.2 eM (LOD
55.41) tussen die merkers, is geïdentifiseer. KKL-kartering het getoon dat KKL in
albei koppelingsgroepe aanwesig is. Twee kommersieël beskikbare, rekombinant-ingeteelde families (Burr et aI.,
1988) is gebruik om die omgeskakelde AFLP-merkers op die mielie genetiese
kaart te plaas. Die KKL wat met die AFLP-merkers geïdentifiseer is, is gekarteer
op chromosome 1 en 5. 'n Verdere AFLP-merker is op chromosoom 2 gekarteer
en 'n ander op chromosoom 3.
Ten einde die KKL op chromosome 1 en 5 meer akkuraat te karteer, is volgordege-
etikeerde en mikrosatelliet merkers gebruik. Die merkers is geamplifiseer op
die DNA van die 230 plante van die F2-populasie en koppelings-analises is
uitgevoer. Die volgorde van die merkers was dieselfde as die van die UMC-kaart
in die Mielie Genoom Databasis. Interval kartering met MAPMAKER/QTL en
komposiet interval kartering met QTL Cartographer is uitgevoer. Die KKL op
chromosoom 1 het 'n LOD-telling van 21 gehad en is in bin 1.05/06 geplaas. Die
KKL was verantwoordelik vir 37% van die variansie. Twee pieke was
onderskeibaar vir die KKL op chromosoom 5, een in bin 5.03/04 geleë en die
ander in bin 5.05/06. Elke piek het 'n LOD-telling van 5 gehad en die twee KKL
was verantwoordelik vir 11% van die variansie.
Om die herhaalbaarheid van die effek van die KKL te toets is die merkers naaste
aan elke KKL geamplifiseer op geselekteerde plante van twee F2-populasies wat
in opeenvolgende jare geplant is. Regressie analise is op die data gedoen. Beide
die KKL op chromosoom 1 en die KKL op chromosoom 5 kon in hierdie
populasies geïdentifiseer word. Verder kon die aanwesigheid van 'n verdere KKL
op chromosoom 3 in hierdie populasies bevestig word. Laasgenoemde KKL was
verantwoordelik vir 8-10% van die totale variansie.
In hierdie studie is daar dus 'n hoof GBV-weerstands KKL gekarteer op
chromosoom 1 en twee kleiner GBV-weerstands KKL gekarteer op chromosome
3 en 5. Merkers is geïdentifiseer wat moontlik in merker-gebaseerdetelingsprogramme
gebruik kan word om plante te selekteer wat die GBVweerstands
KKL het.
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Ecology of Xanthomonas campestris pv. vitians in relation to development of bacterial leaf spot of lettuce by Vicky Toussaint.Toussaint, Vicky. January 2001 (has links)
In Quebec, bacterial leaf spot of lettuce was observed for the first time in 1994. Since this first mention, the disease has been observed each year and the severity varied with environmental conditions. Little information was available on this disease because until recently it was only sporadically observed around the world following the first mention in 1918. In this project, we found that two groups of Xanthomonas caused the bacterial leaf spot of lettuce according to the BIOLOG profiles. From the results of strain characterization, a semi-selective medium has been developed to detect and quantify X. campestris pv. vitians. This medium is made of maltose, tryptone, methyl green, phosphate salts, amoxicillin, cephalothin, cycloheximide and trace elements. It allowed us to carry out studies on the ecology of the pathogen and on the disease epidemiology. The effect of weather conditions on bacterial population size and the bacterial leaf spot development has been studied. Weather parameters influencing the bacterial population were the number of hours with temperature higher than 28°C, the number of hours with wind velocity lower than 1 km per hour, the number of hours with relative humidity lower than 45% and the minimum relative humidity. The weather parameters that significantly discriminated between disease increase categories were the mean solar radiation, the number of hours with relative humidity higher than 90%, the mean relative humidity and the maximum temperature. Looking at the relationship between X. campestris pv. vitians population size and host plant development, it was shown that both bacterial population size and disease severity increased with leaf age. Mathematical models were developed to show these relationships. This information will be useful in disease management to decide when to apply bactericides and when to harvest. Finally, an exploratory study was conducted looking at the effects of nutrients on the size of saprophytic bacterial
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Recurrent selection for gray leaf spot (GLS) and phaeosphaeria leaf spot (PLS) resistance in four maize populations and heterotic classification of maize germplasm from western Kenya /Kwena, Philip Onyimbo. January 2007 (has links)
Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2007. / Full text also available online. Scroll down for electronic link.
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Ecology of Xanthomonas campestris pv. vitians in relation to development of bacterial leaf spot of lettuce by Vicky Toussaint.Toussaint, Vicky. January 2001 (has links)
No description available.
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Studies on Phyllosticta and Coniothyrium occuring on apple foliageCrabill, C. H. January 1913 (has links)
Master of Science
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Inheritance of reactions to gray leaf spot and maize dwarf mosaic virus in maize and their associations with physiological traitsDonahue, Patrick J. January 1989 (has links)
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). / Ph. D.
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