Efficiency of Recurrent Selection by Marker and Phenotype for Multiple, Quantitative Yield Components in Four Cucumber Populations

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  • 1 University of Wisconsin Madison, Horticulture, Madison, WI, 53706

Four cucumber (Cucumus sativus L.) inbred lines were intermated then bulked maternally to create four base populations denoted as cycle 0 (i.e., Pop.1 C0, Pop.2 C0, Pop.3 C0, Pop.4 C0). Each of these populations underwent phenotypic selection (PHE; open-field evaluations), selection by marker (MAS; genotyping at 20 marker loci), and random mating (RAN; no selection) for three cycles. The four traits under selection, multiple lateral branching (MLB), gynoecious sex expression (GYN), earliness (EAR), and fruit length to diameter ratio (L:D), are quantitatively inherited, controlled by relatively few (two to six) QTL per trait and are directly related to yield. Using the same C0 populations and selection scheme allowed a direct comparison of the effectiveness of MAS and PHE. Because each C0 population varied for any given trait, the response to MAS and PHE was not the same for each population. In general, C0 populations that were inferior for a trait either responded favorably to selection or remained constant, while those with superior trait values either did not change or decreased. Both MAS and PHE provided improvements in all traits under selection in at least one population, with the exception of MAS for EAR. MAS and PHE were equally effective at improving MLB and L:D, but PHE was generally more effective than MAS for GYN and EAR. When considering all traits, responses to PHE were superior in three of the four populations. The population for which MAS was superior, however, showed the only increase in yield (fruit per plant), which was not under direct selection. These results indicate that both MAS and PHE are useful for multi-trait improvement in cucumber, but their effectiveness depends on the traits and populations under selection.

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