No description available.

Historically, most twospotted spider mite, Tetranychus urticae Koch, infestations occurred during the late season near maturity, but since 2005, infestations of cotton have become more common throughout the entire season. Several factors may have contributed to the increasing frequency of mites in seedling cotton, one of which is a shift in production practices from furrow applied aldicarb to neonicotinoid seed treatments for thrips control. Another factor that may impact T. urticae densities in seedling cotton is a shift from pre-plant tillage to conservation tillage or no-till cropping systems. Although the literature confirms that T. urticae can cause extensive cotton yield losses, there is a need to further refine potential late-season yield loss. From 2007 to 2009 a series of experiments were conducted to address these issues. In a series of 12 field experiments, neonicotinoid seed treatments resulted in twospotted spider mite densities greater than those in the untreated check, aldicarb, and acephate treatments. Untreated check and aldicarb treatments had the lowest mite densities. Only aldicarb controlled mites compared to the untreated check. A twospotted spider mite host survey determined that henbit, Lamium amplexicaule L., was the most consistent and preferred host. Carolina geranium, Geranium carolinianum L., cutleaf geranium, Geranium dissectum L., vetch, Vicia spp., volunteer soybean, Glycine max L., purple deadnettle, Lamium purpureum L., and spiny sowthistle, Sonchus asper (L.) Hill, were other frequently infested dicotyledonous species. Herbicide burndown timing in reduced tillage cotton production was not critical, given all weeds were killed before cotton was planted. The herbicide glufosinate was efficacious against T. urticae, providing control equal to low- to mid-rates of labeled acaricides. Including glufosinate in a herbicide burndown program was only beneficial for mite control if living weeds were present at planting. Artificial infestation experiments were adversely affected by unseasonably wet and cool weather. Infestations established at the third true leaf resulted in an average yield loss of 44.7%. It is difficult to make any conclusions about infestations made from first bloom and later because of the difficulty in establishing mite populations later in the season.

D.Phil. / The fungus, Verticillium dahliae, is the causative agent of Verticillium wilt, which results in significant cotton (Gossypium hirsutum) crop losses worldwide. This study contributes to the elucidation of cotton defence responses against V. dahliae. The identification, cloning and characterization of three genes that were differentially expressed in response to elicitation with a cell wall-derived (CWD) V. dahliae elicitor are described. It was hypothesized that the molecular architectures of the three characterized genes are supportive of a role in cotton defence against V. dahliae. As one of these genes was present as two homoeologous copies, this study also reports on the molecular characterization of both homoeologs, thus providing further insight into the processes of genomic evolution between homoeologous loci in allotetraploid cotton. The three genes were initially represented as expressed sequence tags (ESTs), obtained from a previous differential display reverse transcription polymerase chain reaction (DDRT-PCR) study by Zwiegelaar (2003), as part of an MSc project. These ESTs, designated C1B10, C4B5 and C4B4, were differentially induced upon elicitation with a CWD V. dahliae elicitor (Zwiegelaar, 2003). In the present study, the genes represented by the three ESTs were identified and characterized by genome walking and 5‘/3‘ rapid amplification of cDNA ends (RACE). Additionally, PCR and reverse-transcription PCR (RT-PCR) were utilized, where necessary, to obtain internal sequences, not covered by the genome walking and RACE reactions. Through the use of these molecular techniques, the full transcript and genomic sequences of each of the three genes was obtained, including their promoters. The promoter of each gene was analyzed for cis-elements driving gene transcription, through bioinformatic analysis. Furthermore, the copy number of each gene was determined through Southern blot analysis. The genes were translated to reveal their encoded protein sequences. The amino acid sequences were submitted to a basic local alignment (BLAST) search of the NCBI database to identify, and align them with, homologous proteins from other plant species (and those from G. hirsutum, if any). An in silico analysis of the encoded protein of each gene was also performed. This examination included domain architecture, post-translational modification, subcellular location and tertiary structure predictions. This study also involved the isolation of the elicitor from the cell walls of V. dahliae fungal cultures. The potency of the freshly-isolated elicitor was investigated with a triphenyltetrazolium chloride (TTC) viability assay on cotton cell suspensions. Its potential to induce PR-proteins was also explored but these results were inconclusive. In addition, expression studies were performed with real-time PCR (q-PCR), to confirm the up- or down-regulation of each gene upon elicitation of cotton cell suspensions with the CWD V. dahliae elicitor, and to investigate the time frame/kinetics of induction. The gene corresponding to the C1B10 EST was designated GhLIPN as this study revealed that it encodes a lipin protein. Lipins are novel proteins with phosphatidate phosphatase 1 (PAP1) activity, exclusive to eukaryotes. They play a fundamental role in the lipid metabolism of organisms ranging in complexity from yeast to animals and plants. In plants, this role includes lipid membrane remodelling during phosphate (Pi) deficiency. During the study of the GhLIPN gene, it was discovered that it occurred as two distinct homoeologous copies from the A- and D-co-resident genomes of allopolyploid G. hirsutum. The GhLIPN homoeologs were named GhLIPN I and N for Insert present and No insert, respectively, based on the presence or absence of a 13 base pair (bp) insertion/deletion (indel) site in intron 6.

No description available.

Made available in DSpace on 2015-03-26T13:58:39Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1156754 bytes, checksum: ec0b59041b7c6272f3daf112a5c980d1 (MD5) Previous issue date: 2013-12-12 / In Brazil, the control of the boll weevil population has been highlighted by the consolidation of a public-private partnership, through the State Agencies for Animal and Plant Production and Health, Ministry of Agriculture, EMBRAPA, State Foundations, Growers Associations, and State Funds of Incentives for Cotton Production, that coordinate and promote the Programs of Prevention, Control and of Suppression of the Cotton Boll Weevil. These efforts have shown satisfactory results in suppressing the pest over the years, sharply reducing yield losses and reducing insecticide applications. Based on the results of research and experience with the legislative control for implementation of the Programs in the State of Goias, in this study is proposed a legislation to meet the interests of cotton growers that adopt the methodologies of the weevil population suppression. The legislation proposed is based on the guidelines of the International Standards for Phytosanitary Measures - ISPM for determining a Low Prevalence Area of Pest - LPAP for the Boll Weevil - Anthonomus grandis, which will subsidize a government policy aimed at the phytossanitary control of the weevil. / No Brasil, o controle populacional do bicudo-do-algodoeiro vem se destacando pela consolidação de uma parceria pública e privada, através dos Órgãos Estaduais de Defesa Agropecuária, do Ministério da Agricultura, da EMBRAPA, das Fundações Estaduais, das Associações de Produtores e Fundos de Incentivos Estaduais à Cotonicultura, que coordenam e fomentam os Programas de Prevenção, Controle e de Supressão do Bicudo-do-Algodoeiro. Ao longo dos anos essas ações demonstraram resultados satisfatórios na supressão da praga, reduzindo acentuadamente as perdas provocadas e diminuindo as aplicações de inseticidas. Baseando-se nos resultados de pesquisas e na experiência obtida no acompanhamento da fiscalização do controle legislativo para implantação dos Programas de Controle e Supressão no Estado de Goiás, é proposto no presente estudo uma legislação para atender ao interesse dos produtores que realizam as metodologias de supressão populacional do bicudo. A minuta de legislação é baseada nas diretrizes das Normas Internacionais de Medidas Fitossanitárias NIMF, para a determinação de uma Área de Baixa Prevalência da Praga ABPP para o Bicudo-do-Algodoeiro Anthonomus grandis, a qual subsidiará uma política governamental voltada para o controle fitossanitário da praga.