NÃmero de clones por famÃlia, seleÃÃo clonal e seleÃÃo de famÃlias em programas de melhoramento de batata / Number of clones per family and clonal versus family selection in potato breeding programs.

AUTOR(ES)

Maria Cristina Duarte Rios Diniz

DATA DE PUBLICAÇÃO

2002

RESUMO

Potato (Solanum tuberosum L.) breeding programs have the objective of producing superior clones from biparental crosses among many different cultivars. Aiming to get these superior clones breeders evaluate great numbers of clones without giving any attention to the families they came from. Simmonds (1996) suggested that breeders can choose between select clones from the whole population or first select the most promising families and then select the best clones within these selected families. Due to little information available on these matters this study aimed at studying the number of clones needed to represent a family, taking into account genetic and experimental parameters and to check if family selection has any advantage related to clonal selection. Twenty-five families derived from a great range of crosses and belonging to the Potato Breeding Program of Universidade Federal de Lavras (UFLA) were evaluated in a 5 x 5 triple lattice design. Plots had 30 clones from each family, distributed in 3 rows of 10 different clones. Traits evaluated were: tuber yield per plant, percentage of large tubers, average weight of large tubers, average weight of medium sized tubers, and tuber specific gravity. The following conclusions could be made: estimates of environmental coefficient of variation (CVe), genetic coefficient of variation (CVg), heritability and CVg/CVe were maintained constant above 2 clones per plot, showing that families representativeness could be accomplished by as few as 6 different clones. Using the maximal curvature method we were able to establish that 36 clones is enough to represent a family. Genetic variances within families were always higher than between families, showing the great potential to select within-families in breeding programs. The correlation coefficients between family means and the 5%, 10%, 15% and 20% best clones within each family were always increasing, showing that within the best families are the best clones.

ASSUNTO(S)

tamanho de famÃlia clones melhoramento genÃtico vegetal melhoramento vegetal parÃmetro genÃtico seleÃÃo potato genetics parameters clone batata plant breeding family size selection

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