Marcos Laux de Leão

Caracterização de espécies diploides de Lotus em resposta à toxidez por alumínio

The objective of this work was to characterize diploid species, including Lotus japonicus model species and recombinant inbred lines of the Lotus genus for resistance to aluminum (Al) toxicity by using acid soil and nutrient solution. The experiments were conducted in greenhouse, being tested three diploid species (L. japonicus MG-20 and GIFU, L. filicaulis and L. burtii), and 180 recombinant inbred lines. In the experiments with diploid species, alfalfa was used as a check, and in the experiments with recombinant inbreed lines, GIFU model species was used. In the soil experiments, the morphological characteristics of the aerial part and the root were evaluated, and in the nutrient solution experiment, only the root length and growth were evaluated. MG-20 and GIF model species were the most productive in general. The results in nutrient solution followed the response pattern similar to the one observed in acid soil evaluations. The MG-20 genotype was superior to the others in all Al concentrations tested. Of the 180 recombinant inbred lines tested, 24 were superior and 39 inferior to the GIFU species. The great diversity observed in the model species and in the recombinant inbred lines can help in future selection of cultivated genotypes (tetraploids) inasmuch as they have a group of developed molecular markers which can be used at identification of regions responsible for higher or lower tolerance to aluminum toxicity.

Construção e avaliação agronômica de genótipos de cornichão com respostas contrastantes à toxidez por alumínio

The objective of this study was to select and characterize Lotus corniculatus genotypes with contrasting responses to toxicity by aluminum. Four cultivars (Sao Gabriel, San Gabriel, Draco, Estanzuela) and one population (UFRGS) were submitted to two consecutive selections in soils that presented 30-35% aluminum saturation. Selections consisted of separating 1% of the most and less vigorous individuals in order to obtain tolerant and sensitive genotypes, respectively. The individuals chosen were compared with the original germplasm by agronomical evaluation. Genotypes selected by tolerance to toxic aluminum were overall superior to the original populations. However, the materials chosen by sensitivity were inferior to the original populations even in situations where toxic aluminum was absent. Among the selected genotypes, the UFRGS selected for tolerance stood out, presenting an elevated dry matter production level - superior to all other genotypes. Field testing and seed multiplication of these genotypes for further use in areas that present this limitation is necessary, especially for the UFRGS population selected for tolerance to aluminum.

Avaliação agronômica de linhagens de aveia-branca em duas regiões fisiográficas do Rio Grande do Sul

Realizou-se neste estudo uma avaliacao inicial em diversas linhagens de aveia-branca (Avena sativa, L.), com o intuito de verificar o desempenho agronomico e identificar os genotipos promissores para o lancamento de cultivares para producao de forragem. Os experimentos foram conduzidos em duas regioes fisiograficas do estado do Rio Grande do Sul, Depressao Central e Campanha Gaucha, nos anos de 2008 e 2009. Foram implementados em blocos casualizados com quatro repeticoes. Cada parcela foi constituida por uma linha de 2 m de comprimento, espacadas a 40 cm entre si, considerando parcela util o metro linear central, cortadas a uma altura de 10 cm. Foram avaliadas 21 linhagens de aveia-branca mais a testemunha (IPR126). No primeiro ano, tambem foram avaliadas duas linhagens de triticale, as quais apresentaram baixo potencial forrageiro e foram excluidas dos experimentos no segundo ano. Na avaliacao do potencial produtivo das linhagens de aveia-branca, nao houve diferencas ocasionadas pela interacao dos fatores local, ano e linhagem. No primeiro ano, os valores medios de producao na Depressao Central e Campanha Gaucha foram de 82,3 e 76,3 g por metro linear de materia seca total, respectivamente. Na avaliacao do segundo ano, as medias de producao para esta especie na Depressao Central e na Campanha Gaucha foram, respectivamente, 80,0 e 119,8 g m-1 de materia seca total. As linhagens de aveia-branca, em sua maioria, apresentam bons resultados e sao promissoras para o programa de melhoramento genetico dessa especie.