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.
Solanum tuberosum L.; relative contribution; morphologic characters
