Genetically modified cotton (Gossypium hirsutum L.) acreage has increased dramatically over the last six years. Reports of variable results in fiber quality and yield have arisen in these cultivars. Some changes in production practices have occurred coincident with the introduction of transgenic technology, such as reduced use of broad-spectrum insecticides, including organophosphates (OP) that could potentially influence the growth and yield of cotton. One factor that might affect these parameters is the difference in the amount of foliarly-applied phosphorus (P) between an OP and non-phosphate (NP) insecticide regime. Therefore, a study was conducted to investigate selected growth characteristics, yield, and fiber quality of genetically modified and conventional cotton as influenced by OP and foliar phosphorus (FP) applications. A four replication strip-plot experimental design was utilized with cultivar serving as the whole plot and insecticide regime as the sub-plot. Three cultivars of the same recurrent parent (ST4892BR, ST4793R, and ST474) were planted in 2001 and 2002 under irrigated conditions in Burleson County, TX on a Weswood silty clay loam (fine-silty, mixed, thermic Fluventic Ustochrept). The insecticide regime consisted of NP, NP+FP, and OP treatments. The FP was applied at P2O5 weight equivalent to the P component in the concurrent OP application. ST4892BR had greater lint yield than ST4793R and ST474. The yield increase can be explained through plant mapping analysis which showed ST4892BR producing larger bolls and greater boll numbers. In addition, evaluation of fruiting distribution showed ST4892BR contained more lint on sympodial branches 6 through 10. The insecticide regime effect on lint yield resulted in higher yield (P=0.08) for the NP+FP regime. Examination of yield components revealed NP+FP increased second position bolls, predominantly at sympodial branches 6 through 10. Leaf tissue analysis revealed increased levels of P for the OP and NP+FP over that of the NP insecticide regime, which indicates a potential for plants to acquire P from OP insecticides. Furthermore, the considerable yield response to small amounts of FP is not clearly understood. While conclusive evidence exists regarding cultivar yield differences, this study does not provide sufficient evidence to conclude that OP insecticides influence growth, yield, or fiber quality characteristics of these cotton cultivars.

Genetically modified cotton (Gossypium hirsutum L.) acreage has increased dramatically over the last six years. Reports of variable results in fiber quality and yield have arisen in these cultivars. Some changes in production practices have occurred coincident with the introduction of transgenic technology, such as reduced use of broad-spectrum insecticides, including organophosphates (OP) that could potentially influence the growth and yield of cotton. One factor that might affect these parameters is the difference in the amount of foliarly-applied phosphorus (P) between an OP and non-phosphate (NP) insecticide regime. Therefore, a study was conducted to investigate selected growth characteristics, yield, and fiber quality of genetically modified and conventional cotton as influenced by OP and foliar phosphorus (FP) applications. A four replication strip-plot experimental design was utilized with cultivar serving as the whole plot and insecticide regime as the sub-plot. Three cultivars of the same recurrent parent (ST4892BR, ST4793R, and ST474) were planted in 2001 and 2002 under irrigated conditions in Burleson County, TX on a Weswood silty clay loam (fine-silty, mixed, thermic Fluventic Ustochrept). The insecticide regime consisted of NP, NP+FP, and OP treatments. The FP was applied at P2O5 weight equivalent to the P component in the concurrent OP application. ST4892BR had greater lint yield than ST4793R and ST474. The yield increase can be explained through plant mapping analysis which showed ST4892BR producing larger bolls and greater boll numbers. In addition, evaluation of fruiting distribution showed ST4892BR contained more lint on sympodial branches 6 through 10. The insecticide regime effect on lint yield resulted in higher yield (P=0.08) for the NP+FP regime. Examination of yield components revealed NP+FP increased second position bolls, predominantly at sympodial branches 6 through 10. Leaf tissue analysis revealed increased levels of P for the OP and NP+FP over that of the NP insecticide regime, which indicates a potential for plants to acquire P from OP insecticides. Furthermore, the considerable yield response to small amounts of FP is not clearly understood. While conclusive evidence exists regarding cultivar yield differences, this study does not provide sufficient evidence to conclude that OP insecticides influence growth, yield, or fiber quality characteristics of these cotton cultivars.

Submitted by (edna.saturno@ufrpe.br) on 2016-11-28T13:38:03Z No. of bitstreams: 1 Maria Esmeralda Cavalcante de Sousa.pdf: 1237941 bytes, checksum: 5d11b8c813aa997680f772fa30705f65 (MD5) / Made available in DSpace on 2016-11-28T13:38:03Z (GMT). No. of bitstreams: 1 Maria Esmeralda Cavalcante de Sousa.pdf: 1237941 bytes, checksum: 5d11b8c813aa997680f772fa30705f65 (MD5) Previous issue date: 2009-02-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) is an important cotton pest in Brazil, occurring almost in the whole growing season and causing economic losses between 21 and 35%. Bt cotton expressing Cry1Ac protein, a toxin from the bacterium Bacillus thuringiensis (Berliner) (Bt), has recently been released in Brazil. It is resistant to the main cotton lepidopteran pests occurring in Brazil. Bt toxins must interact with a receptor to trigger a toxic effect, although other endogenous factors may account for the differential Bt toxins selectivity towards insects. Therefore, studies on the Cry1Ac interaction with the cotton pests midguts are important to understand insect responses when exposed to the Bt cotton. Then, the aim of this work was to provide an histochemical, morphological, and ultrastructural description of the midgut of A. argillacea larvae fed with the isoline cotton (AcalaDTL-90) and the Bt cotton (AcalaDTL-90B). The morphological, histochemical, and ultrastructural characteristics of the A. argillacea midgut were very similar to those previously described for most lepidopterans. However, the mitochondrial polymorphism and bifurcate microvilli suggest an ultrastructural and physiological modification, which may cause a higherabsorption and secretion in the columnar cells. Such hypothesis may account for faster toxin and/or microbial agent action, suggesting that this species may be highly susceptible to some ofthese agents. After 20 min, A. argillacea 4th-ínstar larvae feeding on Bt cotton leaves (AcalaDTL-90B) showed alterations on the midgut walls. During that time, morphological and ultrastructural alterations in the goblet and columnar cells were observed, although more prominent on the former. Also, a reduced number of regenerative cells, a deterioration of the muscle layer, and the peritrophic membrane destruction in some midgut regions were observed. The study overall conclusion is that the Cry1Ac toxin acts relatively fast in the A. argillacea midgut, causing severe and irreversible alterations. / Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) é a principal praga desfolhadora da cultura do algodão, provocando perdas entre 21 e 35%. Plantas transgênicas que expressam proteínas tóxicas de genes da bactéria Bacillus thuringiensis (Berliner) (Bt) foram recentemente liberadas no Brasil. O algodão Bt AcalaDTL-90B, que expressa a proteína Cry1Ac, é resistente às principais pragas da Ordem Lepidoptera que afetam a cultura do algodão.. Embora as toxinas de Bt interajam com pelo menos um receptor final, desencadeando o efeito tóxico, vários fatores endógenos estão associados à seletividade diferencial das toxinas Bt. Desta forma, estudos da interação da Cry1Ac com o intestino de insetos pragas do algodoeiro são de fundamental importância. Assim, esta pesquisa objetivou descrever histoquimicamente, morfologicamente e ultra-estruturalmente o mesêntero de larvas de A. argillacea alimentadas com a isolinha (AcalaDTL-90), bem como algodão-Bt (AcalaDTL-90B). As características morfológicas, histoquímicas e ultra-estruturais do mesêntero de A argillacea, de modo geral, foram semelhantes às descritas na literatura para a maioria dos insetos da Ordem Lepidoptera. No entanto, opolimorfismo mitocondrial e microvilosidades bifurcadas sugerem uma modificação ultra-estrutural e fisiológica, que pode ocasionar uma maior absorção e secreção nas células colunares. Tal hipótese pode favorecer uma ação mais rápida de toxinas e/ou agentes microbianos,sugerindo que esta espécie pode ser altamente suscetível para alguns destes agentes. Larvas de 4º ínstar após 20 min de alimentação com folhas de algodão Bt (AcalaDTL-90B) mostraram modificações na parede do mesêntero de A. argillacea. Neste tempo de alimentação, foram observadas alterações morfológicas e ultra-estruturais nas células colunares e caliciformes, sendo mais expressivas nessas últimas. Também houve uma redução no número das células regenerativas, degeneração da camada muscular e destruição da membrana peritrófica em algumas regiões do mesêntero. Assim, conclui-se que a toxina Cry1Ac age relativamente rápida no mesêntero da A. argillacea, ocasionando alterações drásticas e irreversíveis.