Maize (Zea mays L.) is grown in a wide range of environments and altitudes worldwide. Maize has transitioned from open pollinated varieties to single cross hybrids over the last century. While maize production and genetic gain has increased, genetic diversity among U.S. maize hybrids has narrowed. Problems, such as insect pressure, diseases, and mycotoxins, present obstacles for breeders. One approach is to use exotic germplasm in breeding programs to provide useful, novel alleles for productivity, grain quality, and disease resistance. Little exotic germplasm has been used, because of lack of agronomic adaptation and problems with lodging, earliness, and tall plants in more temperate areas. Using exotic elite materials and evaluating them in targeted regions might increase success. Objectives of this research were: to characterize and evaluate agronomic adaptation and performance of Argentine commercial hybrids in the U.S., to evaluate semi-exotic testcrosses developed from semi adapted 100% tropical lines and elite U.S. inbred LH195, and to estimate response to aflatoxin contamination of Argentine hybrids and semi-exotic testcrosses under inoculation with Aspergillus flavus. Agronomic data was collected during 2004 in eleven Texas environments for Argentine hybrids, and eight Texas environments for semi-exotic testcrosses. Response to aflatoxin was measured in three southern Texas environments. U.S. commercial hybrids were used as checks. Significant differences among hybrids were observed for most environments and traits. In general, Argentine hybrids yielded lower, had lower 1000 kernel weights, and greater test weights than U.S. hybrids. Hybrids AX889, AX882MG, and AX890MG were competitive with U.S. hybrids for grain yield and were stable across environments. Semi-exotic testcrosses had similar lodging and grain moisture percentages, heavier test weights and competitive grain yields compared with U.S. hybrids. Hybrid TX-LAMA2002-9-2-B/lH195 had the highest overall grain yield mean for semi-exotic testcrosses and yielded better than two U.S. hybrids. Argentine hybrids had lower aflatoxin concentration than U.S. hybrids; several hybrids had less than 50 ng g-1 aflatoxin. Semi-exotic testcrosses had reduced aflatoxin compared to U.S. hybrids, with several hybrids under 35 ng g-1. These elite, exotic materials show promise for breeding programs, with competitiveness for grain yield, kernel traits, and reduced aflatoxin levels.

Desired base upper half mean length (UHML) of upland cotton (G. hirsutum) in the U.S. has been set a 27.0 mm and is shorter than the standard set by the international community. Upland cotton genotypes from China, South Africa, West Africa, and the U.S. were test crossed to an extra long staple upland (ELSU) and a short staple upland (SSU) and selected genotypes that included both ELSU and MSU phenotypes were crossed in a half-diallel mating scheme to estimate general combing ability (GCA) effects and specific combining ability (SCA) effects. A recombinant inbred line (RIL) population was established to determine the narrow sense heritability (h^2) of AFIS short fiber content by weight (SFCw) and lower half mean length (LHML) and to estimate SFCw using HVI fiber properties. Obsolete cultivars from China are not likely sources for UHML improvement, cultivars from Africa and the U.S. could harbor alleles not being used in current elite short staple cultivars or modern ELSU cultivars. Two ELSU lines used in this study derived through interspecific hybridization with G. barbadense could contain alleles for UHML improvement in modern ELSU cultivars developed without any apparent G. barbadense introgression. A third line D&PL 45-867, might contain alleles for UHML improvement in long staple upland cotton genotypes. Narrow sense heritability estimates indicated a much higher heritability of LHML than AFIS SFCw. Correlation between AFIS SFCw and LHML did not agree with previous studies when using an ELSU X MSU cross. Further study is needed to understand this complex relationship.

Made available in DSpace on 2016-06-02T20:21:21Z (GMT). No. of bitstreams: 1 2646.pdf: 870244 bytes, checksum: b88bf96aa8cafe0798c953895db021a7 (MD5) Previous issue date: 2009-08-28 / Financiadora de Estudos e Projetos / A preliminary genetic linkage map was constructed for the species Prochilodus argenteus, an endemic fish from the São Francisco river basin, using 23 microsatellite markers in a progeny with 95 individuals from a single cross by the pseudo-testcross strategy. The male and female parents were collected in different regions, downstream of the dam of the Três Marias (MG). Only 11 (52.4%) markers grouped in some linkage group and the the remaining was unlinked. Twenty-one (91.5%) markers appeared to segregate according to Mendelian inheritance, and only two (8.7%) showed segregation distortion. The map covered 297.58 cM of the genome, according to the Kosambi s function. The number of linkage groups (3) found in this study was much lower than expected for the species (equivalent to the haploid number of chromosomes, n = 27), demonstrating the importance of using a larger number of molecular markers in future studies. The data obtained in this work will be compiled with the marks obtained by AFLP by Rojas (2008) in order to obtain a denser genetic map. Although the number of linkage groups found have been lower than expected for the species, the results can be considered promising for the Brazillian Fish Genetics, since genetic mapping studies are virtually absent in Neotropical fish. / Um mapa genético preliminar foi construído para a espécie Prochilodus argenteus, um peixe endêmico da bacia hidrográfica do rio São Francisco, através de 23 marcadores moleculares microssatélites em uma progênie com 95 indivíduos provenientes de um único cruzamento através da estratégia pseudo-testcross . Os genitores masculino e feminino foram coletados em diferentes regiões, à jusante da barragem de Três Marias (MG). Apenas 11 (52.4%) marcadores foram alocados em algum grupo de ligação e os restantes não estavam ligados. Vinte e um (91.5%) marcadores segregaram de acordo com a herança mendeliana e apenas dois (8.7%) apresentaram distorção da segregação. O mapa cobriu 297.58 cM do genoma, de acordo com a função de Kosambi. O número de grupos de ligação (3) encontrado no presente trabalho foi muito inferior ao esperado para a espécie (equivalente ao número de cromossomos haplóides, n = 27), demonstrando a importância da utilização de um número maior de marcadores moleculares em estudos futuros. Os dados obtidos no presente trabalho serão compilados com as marcas AFLP obtidas por Rojas (2008), visando um mapa genético mais denso. Embora o número de grupos de ligação encontrado tenha sido inferior ao esperado para a espécie, os resultados podem ser considerados como promissores na área de Genética de Peixes do Brasil, já que estudos de mapeamento genético são praticamente inexistentes em peixes neotropicais.