Douglas Willian Nogueira

heterose e capacidade combinatória de linhagens de tomateiro ricas em acilaçúcares

Com o presente trabalho, objetivou-se estimar a capacidade combinatoria de linhagens de tomate ricas em acilacucares (AA) quando cruzadas com linhagens com baixo teor de acilacucares e estudar a expressao da heterose nos hibridos obtidos. O experimento foi realizado no campo da HortiAgro Sementes Ltda, localizada em Ijaci-MG. O material genetico foi constituido de seis hibridos experimentais em esquema de dialelo parcial, constituido de tres genitores masculinos (grupo I, com altos teores de acilacucares) e dois genitores femininos (grupo II, com baixos teores). Foram avaliadas as caracteristicas: massa media de fruto (g fruto-1) e producao por hectare (t ha-1). As linhagens TOM-687 e TOM-688 (ricas em AA e resistentes a pragas) apresentaram estimativas positivas dos efeitos de capacidade geral de combinacao, para massa media de frutos, e estimativas negativas, para producao, o que significa que elas contribuiram positivamente para aumento no tamanho do fruto, mas reduziram a produtividade dos hibridos. Ja a linhagem TOM-689, ao contrario das duas anteriores, contribuiu para reduzir o tamanho do fruto, mas contribuiu para aumentar a produtividade dos hibridos. Os hibridos obtidos do cruzamento de linhagens com altos teores de acilacucares mostraram-se competitivas quando comparadas a hibridos comerciais encontrados no mercado. As melhores combinacoes hibridos foram obtidas quando as linhas com altos teores de acilacucares foram cruzadas com a linhagem elite TOM-684.

Caracterização de genótipos de tomateiro resistentes a begomovírus por marcador molecular co-dominante ligado ao gene Ty-1

The objectives of this study were to evaluate tomato genotypes for begomovirus resistance and to assess SSR-47 fingerprinting patterns associated with alleles Ty-1, in hybrids of fresh-market tomato with commercial potential. Twenty-four experimental genotypes, heterozygous at Ty-1 locus, were infected with begomovirus via grafting, and showed intermediate symptoms compared to the ones identified by homozygous Ty-1/Ty-1 lines and by susceptible genotypes Ty-1+/Ty-1+, which indicates the incomplete dominance of the Ty-1 allele. These hybrids were considered to possess partial resistance to begomovirus. The experimental hybrids TEX-246, TEX-261, TEX-253, TEX-256, TEX-262, TEX-252, TEX-251 and TEX-268 combined high total yields with high mean fruit mass. The hybrids TEX-246, TEX-253, TEX-256, TEX-262 and TEX-252 showed also longer half-life for fruit firmness and were thus considered competitive with current commercial hybrids used as checks. The molecular marker SSR-47 was effective for fingerprinting of tomato genotypes bearing the resistance allele Ty-1. The graft-induced infection of begomovirus showed symptoms in the genotypes tested that are in agreement with the results of fingerprinting with the marker SSR-47.

Combining ability of summer-squash lines with different degrees of parthenocarpy and PRSV-W resistance

The aim was to assess heterosis in a set of 16 summer-squash hybrids, and evaluate the combining capacity of the respective parental lines, which differed as to the degree of parthenocarpy and resistance to PRSV-W (Papaya Ringspot Virus-Watermelon strain). The hybrids were obtained using a partial diallel cross design (4 × 4). The lines of parental group I were 1 = ABX-037G-77-03-05-01-01-bulk, 2 = ABX-037G-77-03-05-03-10-bulk, 3 = ABX-037G-77-03-05-01-04-bulk and 4 = ABX-037G-77-03-05-05-01-bulk, and of group II, 1′ = ABX-037G-77-03-05-04-08-bulk, 2′ = ABX-037G-77-03-05-02-11-bulk, 3′ = Clarice and 4′ = Caserta. The 16 hybrids and eight parental lines were evaluated for PRSV-W resistance, parthenocarpic expression and yield in randomized complete-block designs, with three replications. Parthenocarpy and the resistance to PRSV-W were rated by means of a scale from 1 to 5, where 1 = non-parthenocarpic or high resistance to PRSV-W, and 5 = parthenocarpic or high susceptibility to PRSV-W. Both additive and non-additive gene effects were important in the expression of parthenocarpy and resistance to PRSV-W. Whereas estimates of heterosis in parthenocarpy usually tended towards a higher degree, resistance to PRSV-W was towards higher susceptibility. At least one F1 hybrid was identified with a satisfactory degree of parthenocarpy, resistance to PRSV-W and high fruit-yield.

Assessment of resistances to multiple pathogens in experimental sweet pepper hybrids

The aim of this study was to assess resistance to major sweet pepper pathogens ( Phytophthora capsici, Pepper yellow mosaic virus – PepYMV and Meloidogyne incognita ) in a group of experimental hybrids and their respective parental lines, and to identity hybrids possibly resistant to all three pathogens. Ten parental breeding lines, thirty experimental hybrids and seven commercial controls (Konan-R, Magali-R, Martha-R, Stephany, Mallorca, Magnata Super and Criollo de Morelos-334) were used. Each experiment was set up in a randomized complete block design with three replications. For assessment of resistance to P. capsici and PepYMV, the percent of asymptomatic plants was considered. In evaluating reactions to M. incognita, both the nematode reproduction index and the nematode reproduction factor were calculated. Five hybrids were found with resistant to all three pathogens. For all three pathogens, there was evidence that hybrids with two resistant parental lines showed slightly higher levels of pathogen resistance than those with only one resistant parental line.

Marcador microssatélite associado ao alelo Ty-1 de resistência a Begomovirus em tomateiro

O objetivo deste trabalho foi associar um marcador microssatelite ao alelo Ty-1 de resistencia a Begomovirus em tomateiro, e avaliar a eficiencia desta associacao na selecao de linhagens resistentes ao virus. Os marcadores SSR-47 e SSR-48 foram testados em linhagens isogenicas contrastantes quanto a presenca do alelo Ty-1 (LA-3473, LA-3474, LA-3475). O marcador SSR-47, por ter detectado polimorfismo nas linhagens, foi o unico utilizado nas etapas subsequentes da pesquisa. Detectada a associacao entre o SSR-47 e o alelo Ty-1, testou-se sua eficiencia na selecao de genotipos avancados de tomateiro. Para confirmar a eficiencia da selecao, foi realizada a avaliacao fenotipica das plantas com padroes contrastantes de bandas para SSR-47, quanto a resistencia a Begomovirus. Plantas que apresentaram banda unica de 191 pb foram resistentes ao Begomovirus, pelo teste de inoculacao por enxertia; aquelas com banda unica de 180 pb foram suscetiveis; e as plantas com bandas de 191 e 180 pb foram resistentes. A distância maxima entre o Ty-1 e o marcador SSR-47 foi de 2,7 cM. Este marcador foi efetivo em caracterizar genotipos portadores do alelo Ty-1. As respostas das plantas a infeccao pelo Begomovirus, induzida via enxertia, sao consistentes com as reacoes previstas com o uso do marcador molecular SSR-47.