Alexandre Alves de Carvalho

Avaliação da diversidade genética entre acessos de mamoneira (Ricinus communis L.) por meio de caracteres morfoagronômicos

Genetic divergence is one of the most important breeding parameters evaluated in the initial phase of a genetic improvement program. The objective of this work was to characterize 15 accessions of castor bean using morphoagronomic traits. The trial was carried out in Lavras, MG, Brazil, from February to August 2008. The experimental design was a randomized complete block design with three replicates and 25 plants per plot. The traits evaluated were: plant height (cm), stem height (cm), number of nodes, diameter of stem and number of clusters. Significant differences (F test: P < 0.01) were found for accession effects on all studied traits. Genetic distances among accessions were estimated using the Euclidean method. Four distinct groups were formed using the methods of Tocher and the hierarchical nearest neighbor clustering, based on the Euclidean distance. The results of this work indicate crossings between accessions from groups I and IV, II and IV and III and IV.

Correlações genotípicas, fenotípicas e ambientais entre caracteres de mamoneira

Um dos grandes desafios atuais da pesquisa agricola e a producao de cultivares melhoradas de mamoneira, com estabilidade genetica, alta qualidade e potencial produtivo. Objetivou-se, no presente trabalho, estimar as correlacoes genotipica, fenotipica e de ambiente entre caracteres de mamona para facilitar a caracterizacao dos acessos. Foram avaliados em Lavras, MG, no delineamento de blocos casualizados com tres repeticoes, quinze acessos de mamona. Os caracteres avaliados foram altura da planta, altura do caule, numero de internodios, diâmetro do caule, numero de cachos, estande final e peso de 100 sementes. Observou-se que houve correlacao fenotipica positiva do numero de internodios e altura do caule, altura do caule e altura da planta, altura da planta e diâmetro do caule e por fim entre diâmetro do caule e peso de 100 sementes. Houve tambem correlacao ambiental positiva entre as correlacoes altura de caule e altura de planta, altura de planta e diâmetro do caule, altura da planta e estande final e diâmetro do caule e numero de cachos, concluindo que as correlacoes estimadas possibilitaram conhecer as associacoes entre os caracteres, fornecendo importantes informacoes para o estabelecimento de um plano de melhoramento genetico da mamona, a partir dos acessos avaliados.

Cytokinins in the in vitro multiplication and analysis of the volatile fraction of Hyptis marrubioides

The aim of this study was to evaluate different concentrations of two cytokinins in the in vitro propagation of the medicinal plant Hyptis marrubioides Epl. and to analyse the volatile fraction of the compounds. Nodal segments of plants were inoculated onto Murashige and Skoog (MS) solid medium with different concentrations of benzylaminopurine (BAP) or tidiazuron (TDZ) under a 16/8 h light/dark cycle at 25 ± 2 °C. After 45 days growth, the plants were evaluated for the number and length of the shoots and for shoot dry matter. The volatile constituents were analysed by headspace-GC/MS. The greatest number of shoots was obtained with 1.0 mg L-1 TDZ in the MS medium. The greatest values for shoot length and dry matter were obtained with BAP. Twenty-seven compounds were characterised as constituents of the essential oil of H. marrubioides. The major compounds of the volatile fraction were sabinene, α-thujone, β- thujone, α-copaene, β-caryophyllene, γ-gurjunene and γ-himachalene. The types and concentrations of the growth regulators influenced accumulation of the volatile fraction. Quantitative changes in the monoterpenes and sesquiterpenes in the volatile fraction of the plants were also seen in response to the type of growth regulator added to the culture medium.

Growth and volatiles in the micropropagation of Santa Maria herb

The aims of this study were to establish micropropagation for Chenopodium ambrosioides L. and analysis of volatile constituents in vitro as a function of different salt concentrations of MS medium and sucrose. The apical buds were established on MS medium added with 3% sucrose. The vegetative growth of nodal segments was tested in different salt concentrations of MS basic medium (0.25, 0.50, 1.00, 1.50, and 2.00) and of sucrose (5, 10, 20, 30, and 40 g L-1). Nodal and apical segments were tested in vertical and horizontal orientations. Different volumes of culture medium (20; 35, 50, 65, and 80 mL) were examined in the growth of nodal segments. Plants were acclimatized in three different substrates. The apical segments collected from matrices plants were successful when established in MS medium. A multiplication rate of 8.5 was obtained with nodal and apical segments without using growth regulator. MS medium with its salt concentration reduced by half (0.50 MS) and sucrose at the concentration of 30 g L-1 provided better in vitro growth of nodal segments. Four major volatile compounds (α-terpinene, p-cymene, Z-ascaridole, and E-ascaridole) varied at different salt concentrations and only α-terpinene showed difference for sucrose concentrations. Apical segments in vertical orientation and nodal segments in horizontal with 50 mL of culture medium showed better responses for the in vitro cultivation of C. ambrosioides L.

Colored shade nets induced changes in growth, anatomy and essential oil of Pogostemon cablin

The purpose of this investigation was to determine the influence of colored shade nets on the growth, anatomy and essential oil content, yield and chemical composition of Pogostemon cablin. The plants were cultivated under full sunlight, black, blue and red nets. The harvesting was performed 5 months after planting and it was followed by the analysis of plant growth parameters, leaf anatomy, essential oil content, yield and chemical composition. The plants grown under red net have produced more leaf, shoot, total dry weight and leaf area. Plants cultivated under colored nets showed differences in morphological features. Plants maintained under red net had a higher leaf blade thickness and polar and equatorial diameter of the stomata ratio. Additionally, higher yield of essential oil in the leaves was observed under red and blue colored shade net. The essential oil of the plants grown under red net showed the highest relative percentage of patchoulol (66.84%). Therefore, it is possible using colored shade nets to manipulate P. cablin growth, as well as its essential oil production with several chemical compositions. The analyses of principal components allowed observing that pogostol has negative correlation with α-guaiene and α-bulnesene. There was difference in total dry weight and patchoulol content when the patchouli is cultured under the red colored shade nets.