Roberto Fritsche Neto

Seleção para caracteres componentes de aparência e rendimento de tubérculo em plântulas de batata

The objective of the present research was to estimate the expected gains with correlated selection for tuber yield and general appearance component traits at the seedling stage in potato. Two populations were evaluated at seedling stage (i.e. plantlets obtained from true seeds) cultivated in glasshouse in the Fall and Spring seasons of 2004. Expected gains and gains obtained from selection of genetically correlated traits were estimated in the two experiments. For some traits the expected correlated gains could be obtained at the seedling generation, being, therefore an alternative to increase selection efficiency, especially with traits of low heritability. The tuber curvature was the trait that provided the largest expected correlated gains for general tuber appearance.

Consistency of two stability analysis methods in potatoes

The objective of this research was to compare the consistency of the bi-segmented and AMMI (additive main effects and multiplicative interaction analysis) methods for estimating yield stability in potatoes. Data of ten genotypes evaluated in 34 environments (local, growing season and year combinations) of the Rio Grande do Sul state, Brazil, in 1994 and 1995 were used. Three data sets were analyzed: 34-environment data set and two 17-environment data subsets, which were chosen by randomly dividing the total data set. For the 34-environment data set, the models gave similar results in relation to the stable genotypes, but they differed with regard to the unstable genotypes. For the 17-environment data sets, the bi-segmented model showed more consistent results, either between subsets or between these and the total data set. For the AMMI model, only the Santo Amor genotype showed consistency between one of the subsets and the total data set. In this work, the bi-segmented method was shown to be more consistent than the AMMI model.

Repetibilidade e importância de caracteres para avaliação de coleção ativa de germoplasma de batata

As the genetic base of the cultivated potato (Solanum tuberosum L.) is narrow, it is important to use the existing germplasm in the breeding programs, associated with an efficient characterization method. We verified the repeatability, the necessary number of evaluations and the relative importance of phenotypic characters in the characterization of an active potato germplasm bank. A group of 77 potato cultivars and elite clones was cultivated in the experimental field of Embrapa Clima Temperado, on spring seasons of the years 1999, 2000, 2001, 2002 and 2003. The plots consisted of a single row of 15 plants, spaced 0.30 x 0.80 m, within and between rows, respectively. Thirty-three plant and tuber descriptors characters were evaluated. The data were submitted to the analysis of variance, repeatability and importance of characters. Stem pigmentation and color intensity of the sprout base are the more important characters to characterize the potato germplasm, either by the percentage of contribution or by the repeatability of the expression in the various growing years, reflecting in a reduced number of necessary evaluations. The characters leaf coalescence and vein pigmentation, presence of wings, foliage type, leaf insertion, leaflet width, leaflet size, skin color, flower frequency, pubescence of sprout base, peduncle and external corolla pigmentation, apex aspect, and skin roughness showed reduced repeatability and/or small contribution for the dissimilarity. Therefore they should receive less emphasis in the evaluations.