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Methoprene as a protectant against five species of stored-product insects in wheatZeledon, Manuel E. January 1984 (has links)
Call number: LD2668 .T4 1984 Z44 / Master of Science
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Effect of delayed sowing and increased crop density on weed emergence and competition with wheatGaongalelwe, Motlhasedi Olebile. January 2002 (has links) (PDF)
"July 2002" Bibliography: leaves 40-46.
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Studies on the ecology of Rhizoctonia solani Kuhn / by Jacobus Frederik de Beer.De Beer, Jacobus Frederik . January 1965 (has links)
Typescript. / Includes bibliographical references. / 193 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1965
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The distribution, pathogenicity and population dynamics of Pratylenchus thornei on wheat in South AustraliaNicol, Julie. January 1996 (has links) (PDF)
Bibliography: leaves 224-236. The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease.
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Fungal parasitism of cereal aphids in South Africa.Hatting, Justin Louis. 17 December 2013 (has links)
The Russian wheat aphid, Diuraphis noxia is one of the most destructive exotic
invaders of South Africa, capable of reducing individual wheat plant yields by up to
90%. Entomopathogenic fungi are important natural mortality factors associated with
this aphid in its Eurasian endemic habitats as well as in the United States and Canada;
their impact often exceeding that of predators and parasitoids.
The principal objectives of this study included (1) baseline characterization of the
aphid-pathogenic flora associated with aphids from South Africa, with special
reference to six common cereal aphids, (2) quantification of the comparative impact
of the different fungal species on the cereal-aphid complex in three different wheat
producing regions of South Africa, (3) field evaluation of the Hyphomycete
Beauveria bassiana against D. noxia on resistant wheat, (4) screening of six
fungicides for their potential usage in managing entomophthoralean epizootics within
greenhouse rearings of the Russian wheat aphid, and (5) development and evaluation
of a novel bioassay protocol for screening entomopathogenic Hyphomycetes against
D. noxia.
A total of nine species of fungi known to infect and kill aphid hosts were
collected, including the six entomophthoraleans, Pandora neoaphidis, Conidiobolus
thromboides, Conidiobolus obscurus, Entomophthora planchoniana, Conidiobolus
coronatus and Neozygites fresenii, and three Hyphomycetes, Beauveria bassiana,
Verticillium lecanii, and Paecilomyces farinosus. The former four
entomophthoraleans are considered first reports from this country. For the first time,
morphological characteristics of these nine South African-collected species are
visually depicted and techniques for their isolation and in vitro culture discussed.
Seven species of fungi were recorded from D. noxia, of which P. neoaphidis was
the most important, causing up to 50% mortality during the late season under dryland
conditions in the summer-rainfall region. Mycoses at epizootic levels, together with
the large diversity of fungal species recorded from this host, indicated a high level of
susceptibility to fungal infection. In contrast, infection of the oat aphid
Rhopalosiphum padi remained < 5% despite favourable numbers of hosts and
apparently suitable environmental conditions. This phenomenon strongly suggests
some level of low susceptibility to fungal infection in this species. Under irrigated conditions m KwaZulu-Natal, the rose-gram aphid
Metopolophium dirhodum was the predominant aphid but remained below economical
injury levels. Field surveys revealed that this aphid was effectively targeted by P.
neoaphidis and C. obscurus, and findings suggest that in some areas of South Africa
entomophthoralean fungi effectively suppress this aphid, negating the need for
insecticide applications.
On average, ca. 61% control of D. noxia on resistant wheat was observed
following an application of B. bassiana (5 x 10¹³ conidia per hectare) during the early
flag-leaf stage of the wheat. Efficacy of B. bassiana applications on younger plants
appeared to be influenced by the level of aphid activity, possibly explained by
secondary pick-up of inoculum by D. noxia. These findings accentuate the importance
of understanding the tritrophic relationship between host plant, pest and pathogen.
The fungicides copper oxychloride, mancozeb + oxadixyl, captab + metalaxyl,
bittertanol, iprodione, and mancozeb at a rate of 0.1% active ingredient moderately to
strongly inhibited C. thromboides vegetative growth (mean inhibition 81.1 %).
Mancozeb at concentrations of 10.0, 2.0, 1.25, 0.5, 0.08, and 0.016% was further
evaluated in vitro. The fungus growth cut-off point, midway between 1.25 and 2.0%
mancozeb, was calculated and a rate of 1.625% active ingredient per litre of water was
used to decontaminate the fungus-infected D. noxia cultures.
A novel bioassay protocol was developed, employing live host plants for rearing
aphids post inoculation. Using this design against D. noxia, an average LC₅₀ estimate of 85 conidia per mm² for B. bassiana strain GHA was calculated. Control mortality
was restricted to levels below 4%. The data indicated high precision due to an average coefficient of variation for slope of less than 20%, and an average chi-squared value
of 5.46 ± 2.74 (n = 10 assays). The design will accommodate the use of cereal aphid species other than D. noxia, while live host plants will facilitate tritrophic studies on the effect of host-plant resistance on fungus-induced mortality of D. noxia. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.
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The distribution, pathogenicity and population dynamics of Pratylenchus thornei on wheat in South Australia / Julie Margaret Nicol.Nicol, Julie January 1996 (has links)
Bibliography: leaves 224-236. / xiv, 236, [16] leaves, [18] leaves of plates : ill. (chiefly col.), map ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997
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Interrelationships between soil-borne pathogens on `Triticum aestivum` / by Bharati K. PatelPatel, Bharati K. January 1983 (has links)
Bibliography: leaves 172-180 / vi, 180 leaves, [29] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1983
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Minimum cultivation and root diseases of wheat / by Stephen Michael NeateNeate, Stephen Michael January 1984 (has links)
Bibliography: leaves 133-144 / viii, 144 leaves, 16 leaves of plates, [3] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1984
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Resistance in `Triticum aestivum` to infection by `Gaeumannomyces graminis` var `Tritici` / by L. PenrosePenrose, L (Lindsay) January 1985 (has links)
Bibliography: leaves 141-145 / vii, 145 leaves, [4] leaves of plates : ill. (4 col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Depts. of Plant Pathology and Agronomy, 1986
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Characterization of the mitochondrial genomes of Diuraphis noxia biotypesDe Jager, Laura-Ellen 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Diuraphis noxia (Kurdjumov, Hemiptera, Aphididae) commonly known as the Russian wheat aphid (RWA), is a small phloem-feeding pest of wheat (Triticum aestivum L). Virulent D. noxia biotypes that are able to feed on previously resistant wheat cultivars continue to develop and therefor the identification of factors contributing to virulence is vital. Since energy metabolism plays a key role in the survival of organisms, genes and processes involved in the production and regulation of energy may be key contributors to virulence: such as mitochondria and the NAD+/NADH that reflects the health and metabolic activities of a cell. The involvement of carotenoids in the generation of energy through a photosynthesis-like process may be an important factor, as well as its contribution to aphid immunity through mediation of oxidative stress. The complete mitochondrial genome of global Diuraphis noxia populations was characterised using Next Generation sequencing, and was found to be 15 721bp in size and consisting of 38 genes typically found within most insects. Single nucleotide polymorphism (SNP) analyses of the genomes of nine populations revealed 125 SNPs in the protein coding genes with the majority of the SNPs occurring in the ND genes, and the least in the ND4L gene. Low SNP variant frequency was found for the atp6 and atp8 genes, which differed from other reports in the Hemiptera. Variable ND5 expression levels were observed among the biotypes, although no correlation was apparent between ND5 expression and the virulence associated with each biotype. Whereas atp6 transcription was higher in the highly virulent biotype (SAM) under normal and stressful conditions in comparison to the least virulent biotype (SA1). A significantly higher NAD+/NADH ratio was also observed for the SAM biotype under stressful conditions in comparison to the lesser virulent biotypes. UPLC-MS analysis did not reveal any lycopene or β-carotene due to low compound concentrations in the extracted samples but various hydrophobic compounds were present in different concentrations among the biotypes. The carotene desaturase expression profile revealed that SA1 had the lowest relative expression of the gene involved in carotenoid products, while SAM had the highest, under normal and stressful conditions. The results indicate that sequence conservation in mitochondrial genes are associated with key energy processes to maintain a state of homeostasis under variable conditions and that the generation of energy is a contributing factor to the virulence development of D. noxia. The results also show that carotenoids may possibly contribute to fitness of D. noxia through reactive oxygen species scavenging or the production of additional energy, but further investigation is needed for confirmation. / AFRIKAANSE OPSOMMING: Diuraphis noxia (Kurdjumov, Hemiptera, Aphididae) algemeen bekend as die Russiese koringluis (RWA), is ‘n klein floëem-voedende pes van koring (Triticum aestivum L). Virulente D. noxia biotipes wat instaat is om op voorheen bestande koring kultivars te voed gaan ontwikkel voortdurend, en daarom is die identifisering van faktore wat kan bydrae tot virulensie so belangrik. Omdat energie-metabolisme ‘n sleutelrol in die oorlewing van organismes speel, kan gene en prosesse wat by die produksie en regulering van energie betrokke is belangrike bydraers tot virulensie lewer: soos onder andere mitokondria en die NAD+/NADH-verhouding wat die gesondheid en metaboliese aktiwiteit van ‘n sel reflekteer. Die betrokkenheid van karotenoïede in die produksie van energie deur 'n fotosintese-verwante proses kan 'n belangrike faktor bydraend tot luis fiksheid wees, asook die bydra daarvan tot plantluis-immuniteit deur bemiddeling van oksidatiewe stres. Die volledige mitochondriale genoom van globale Diuraphis noxia populasies is met behulp van volgende generasie DNA volgordebepaling gekarrakteriseer, en daar is bevind dat dit 15 721 bp in grootte is en uit 38 gene bestaan wat tipies binne insekte voorkom. Enkelnukleotied- polimorfisme (SNP) ontleding van die genome van nege populasies het onthul dat daar 125 SNPs in die proteïen-koderende gene voorkom, met die meerderheid van die SNPs in die ND-gene, en die minste in die ND4L-geen. Lae SNP-frekwensies is gevind vir die atp6- en atp8- gene, wat verskil van verslae oor ander Hemiptera. Veranderlike ND5-uitdrukkingsvlakke onder die biotipes is waargeneem, alhoewel geen korrelasie duidelik was tussen ND5-uitdrukking en die virulensie geassosieer met elke biotipe nie. Die transkripsie van atp6 was hoër in die hoogs virulente biotipe (SAM) onder normale en stresvolle toestande in vergelyking met die minste virulente biotipe (SA1). ‘n Aansienlike hoër NAD+/NADH-verhouding is ook waargeneem vir die SAM-biotipe onder spanningsvolle omstandighede in vergelyking met die minder virulente biotipes. UPLC-MS-analise het geen likopeen of β-karoteen geïdentifiseer nie as gevolg van lae verbinding konsentrasies in die onttrekte monsters, maar verskeie hidrofobiese verbindings was in verskillende konsentrasies tussen die biotipes teenwoordig. Die karoteen desaturase-uitdrukkingsprofiel het aangetoon dat SA1 die laagste relatiewe uitdrukking van gene betrokke by karotenoïed produksie het, terwyl SAM die hoogste relatiewe uitdrukking onder normale en spanningsvolle omstandighede het. Die resultate van die studie dui daarop dat die volgorde bewaring in mitochondriale gene verband hou met die sleutel energie prosesse om 'n toestand van homeostase onder wisselende omstandighede te handhaaf en dat die produksie van energie 'n bydraende faktor tot die ontwikkeling van virulensie in D. noxia is. Die resultate toon ook aan dat karotenoïede moontlik kan bydra tot fiksheid van D. noxia deur reaktiewe suurstofspesies te aas of deur die produksie van addisionele energie, maar verdere ondersoeke word benodig ter bevestiging.
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