Search

Plant breeding aims to develop cultivars with good agronomic traits through gene recombination and elite genotype selection. To support Coffea arabica breeding programs and assist parent selection, molecular characterization, genetic diversity (GD) analyses, and circulating diallel studies were strategically integrated to develop new cultivars. Molecular markers were used to assess the GD of 76 candidate parents and verify the crossing of potential F1 hybrids. Based on the complementary agronomic traits and genetic distance, eight elite parents were selected for circulating diallel analysis. The parents and 12 hybrids were evaluated based on 10 morpho-agronomic traits. For each trait, the effects of general and specific combining abilities, as well as the averages of the parents, hybrids, and predicted hybrids, were estimated. Crosses that maximize the genetic gains for the main agronomic traits of C. arabica were identified. Joint analysis of phenotypic and molecular data was used to estimate the correlation between molecular GD, phenotypic diversity (PD), phenotypic mean, and combining ability. The selection of parents that optimize the allele combination for the important traits of C. arabica is discussed in detail. Made available in DSpace on 2022-01-27T01:58:47Z (GMT). No. of bitstreams: 1 Combining-Ability-and-Molecular.pdf: 2421339 bytes, checksum: b1fd8d047ff3e47af308c96d0c676428 (MD5) Previous issue date: 2021

The use of resistant cultivars is the most effective strategy for controlling coffee leaf rust caused by the fungus Hemileia vastatrix. To assist the development of such cultivars, amplified fragment-length polymorphism (AFLP) markers linked to two loci of coffee resistance to races I and II as well as pathotype 001 of H. vastatrix were converted to sequence-characterized amplified region (SCAR) and cleaved amplified polymorphic site (CAPS) markers. In total, 2 SCAR markers and 1 CAPS marker were validated in resistant and susceptible parents as well as in 247 individuals from the F2 population. The efficiency of these markers for marker-assisted selection (MAS) was evaluated in F2:3 and backcross (BCrs2) populations genotyped with the developed markers and phenotyped with race II of H. vastatrix. The markers showed 90% efficiency in MAS. Therefore, the developed markers, together with molecular markers associated with other rust resistance genes, were used for F3:4 and BCrs3 coffee selection. The selected plants were analyzed using two markers associated with coffee berry disease (CBD) resistance, aiming for preventive breeding. MAS of F3:4 and BCrs3 individuals with all resistance loci was feasible. Our phenotypic and genotypic approaches are useful for the development of coffee genotypes with multiple genes conferring resistance to coffee leaf rust and CBD. Made available in DSpace on 2022-01-27T01:59:16Z (GMT). No. of bitstreams: 1 marker-assisted-pyramiding.pdf: 22779626 bytes, checksum: 7a76b7c036947b04bf1229d56a0e8c4e (MD5) Previous issue date: 2021

Resumo: O objetivo deste trabalho foi avaliar a eficiência da aplicação foliar de fungicidas na redução da incidência de patógenos fúngicos, de grãos ardidos e de fumonisinas totais em grãos de milho (Zea mays). Foram conduzidos três ensaios: um no município de Luís Eduardo Magalhães, na Bahia, e dois em Sete Lagoas, em Minas Gerais, nas safras 2010/2011 e 2011/2012, com cultivo de diferentes híbridos comerciais. Os seguintes fungicidas foram aplicados zero, uma e duas vezes: picoxistrobina + ciproconazol, piraclostrobina + epoxiconazole, trifloxistrobina + tebuconazole, azoxistrobina + ciproconazol e tiofanato metílico. Em todos os ensaios, foram realizados a quantificação da incidência de grãos ardidos, o teste de patologia de sementes e a quantificação dos teores de fumonisinas totais. Não foi observada diferença significativa para os fatores fungicida e número de aplicações, exceto para rendimento de grãos, em todos os ensaios. Esses resultados são indicativos da ineficiência da aplicação de fungicidas na redução da incidência de patógenos fúngicos, de grãos ardidos e dos teores de fumonisinas totais em grãos de milho. Abstract: The objective of this work was to evaluate fungicide leaf application on the reduction of fungal pathogen incidence, kernel rot, and total fumonisins in corn (Zea mays) kernels. Three experiments were performed: one in the municipality of Luís Eduardo Magalhães, in the state of Bahia, and two in the municipality of Sete Lagoas, in the state of Minas Gerais, Brazil, during the 2010/2011 and 2011/2012 crop seasons, with planting of different commercial hybrids. The following fungicides were applied zero, one, and two times: picoxystrobin + cyproconazole, pyraclostrobin + epoxiconazole, trifloxystrobin + tebuconazole, azoxystrobin + cyproconazole, and thiophanate-methyl. For all trials, the quantification of kernel rot incidence, the grain pathology test, and the quantification of total fumonisins were performed. No significant difference was observed for the factors fungicide and number of applications, except for grain yield, in all trials. These results show the ineffectiveness of fungicide applications in reducing fungi incidence, kernel rot, and levels of total fumonisins in corn kernels.

O objetivo deste trabalho foi avaliar a eficiência do uso de multilinhas dinâmicas, por meio de misturas genéticas em populações de híbridos triplos, no manejo da antracnose do sorgo, causada pelo fungo Colletotrichum sublineolum. Foram obtidos 18 híbridos triplos a partir de sete linhagens que continham genes distintos para resistência à doença. Os 25 genótipos de híbridos e linhagens foram avaliados em campo. Verificou-se, em alguns híbridos, grau de resistência superior ao observado para a linhagem mais resistente utilizada nos cruzamentos, o que indica efeito aditivo dos genes de resistência das diferentes linhagens na composição da resistência final dos híbridos. O usodas multilinhas dinâmicas reduziu a intensidade da doença no campo e aumentou a produtividade. Essa estratégia torna possível a utilização de linhagens que apresentam características agronômicas desejáveis, mas são suscetíveis à antracnose. The objective of this work was to evaluate the efficiency of dynamic multilines, using genetic mixing in populations of three-;way hybrids, in the management of sorghum anthracnose, caused by the fungus Colletotrichum sublineolum. Eighteen three-;way hybrids were obtained from seven different lines containing genes for resistance to the disease. The 25 genotypes of hybrids and lines were evaluated in field conditions. In some hybrids, a higher resistance level was observed when compared to that of the more resistant line used in the crosses, indicating an additive effect of the resistance genes of the different lineages in the composition of the final resistance of hybrids. The use of dynamic multilines reduced the disease intensity in field and increased productivity. This strategy makes it possible to use lineages that have desirable agronomic characteristics, but are susceptible to anthracnose.

O objetivo deste trabalho foi identificar marcadores moleculares relacionados à resistência do cafeeiro (Coffea arabica) à ferrugem (Hemileia vastatrix). Foram identificadas sequências de DNA potencialmente envolvidas na resistência do cafeeiro a doenças, por meio de análise "in silico", a partir das informações geradas pelo Projeto Brasileiro do Genoma Café. A partir das sequências mineradas, foram desenhados 59 pares de iniciadores para amplificá-las. Os 59 iniciadores foram testados em 12 cafeeiros resistentes e 12 susceptíveis a H. vastatrix. Vinte e sete iniciadores resultaram em bandas únicas e bem definidas, enquanto um deles amplificou fragmento de DNA em todos os cafeeiros resistentes, mas não nos suscetíveis. Esse marcador molecular polimórfico amplificou uma região do DNA que corresponde a uma janela aberta de leitura parcial do genoma de C. arabica que codifica uma proteína de resistência a doenças. O marcador CARF 005 é capaz de diferenciar os cafeeiros analisados em resistentes e susceptíveis a H. vastatrix. The objective of this work was to identify molecular markers related to the resistance of coffee (Coffea arabica) to rust (Hemileia vastatrix). DNA sequences potentially involved in coffee disease resistance were identified, using "in silico" analysis, from data obtained by the Brazilian coffee genome project. After data mining, 59 primer pairs were designed to amplify the sequences identified. The 59 primers were tested on 12 resistant and 12 susceptible coffee plants to H. vastatrix. Twenty-seven primers resulted in unique and well-defined bands, while one of these amplified a DNA fragment in all resistant plants, but not in the susceptible ones. This polymorphic molecular marker amplified a region of DNA that corresponds to a partial open reading frame of C. arabica genome that encodes a disease resistance protein. The marker CARF 005 can be used to differentiate between resistant and susceptible coffee plants to H. vastatrix.