Abstract
Clonal families from a broad genetic base population in the Potato Breeding Program at the Universidade Federal de Lavras (UFLA), Brazil, were used in this trials. Twenty-five families were assessed in a 5 x 5 triple lattice design. Each plot consisted of 30 clones distributed in three rows of ten plants. Tuber yield per plant, percentage of large tubers, mean weight of large tubers, mean medium-sized tuber weight and tuber specific gravity were measured. Three hundred experiments were simulated varying the family sizes from three to 90 clones. The coefficients of experimental variation (CVe), the coefficients of genetic variation (CVg), heritabilities for family mean and the CVg/CVe ratio were estimated. Genetic parameters were stabilized with family sizes as small as six clones, depending on the trait. This indicates that the families can be adequately represented by a small sample of clones. Using the maximum curvature method it is possible to conclude that approximately 30 clones would be sufficient to represent each family, even for traits with the highest CVe. The genetic variance within family was greater than the genetic variance among families for all traits, indicating a favorable potential for within family selection. The correlation coefficients of the family means with the 5%, 10%, 15% and 20% best clones from each family, considering the five traits assessed, were always high, meaning that within the best families generally are the best clones.
Highlights
The potato (Solanum tuberosum L.) is a vegetatively propagated specie and the breeding programs for this crop aim to produce superior clones
Visual selection reduces the number of clones to be assessed in later generations but even though the large number of clones hinders the use of experimental designs appropriate for assessing many treatments, such as the incomplete blocks designs
Simmonds (1996) claims that genetic variances between and within full sib families should be of similar size and proposes that sets of families be assayed to select only the few best, tested against standards, to be exploited thoroughly
Summary
The potato (Solanum tuberosum L.) is a vegetatively propagated specie and the breeding programs for this crop aim to produce superior clones. These programs start with hybridizations among different pairs of parents or polycrossings to obtain true seeds from which the various clones are derived. Simmonds (1996) claims that genetic variances between and within full sib families should be of similar size and proposes that sets of families be assayed to select only the few best, tested against standards, to be exploited thoroughly. Simmonds (1996) recognizes that a good comparison of these two kinds of genetic variances has never been made. Simmonds (1996) recognizes that a good comparison of these two kinds of genetic variances has never been made. Gopal (2001a) states that little
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