Submitted to: Pickle Packers International Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2005
Publication Date: 10/28/2005
Citation: Staub, J.E., Fan, Z., Sun, Z., Lower, R.L. 2005. Identification and use of yield and fruit quality genes in cucumber. 2005 Pickle Packers International Meeting Proceedings. p. 3. Interpretive Summary:
Technical Abstract: Yield and quality improvements in commercial cucumber are long term, difficult, and expensive. The incorporation of unique plant architectural and fruit developmental traits may potentially improve commercial cucumber. It would be desirable to increase breeding efficiency and shorten the time required for the incorporation of such traits. Recently, a series of cooperative cucumber projects between the USDA and the University of Wisconsin have focused on increasing breeding efficiency by employing molecular marker development as tags for yield and quality traits that include early flowering (days to flower; DTF), more female flowers (gynoecious; GYN), extensive branching (multiple lateral branching; MLB), increased fruit length (length:diameter ratio; L:D) and parthenocarpy. Two cycles of marker-assisted backcrossing for DTF, GYN, MLB, and L:D was completed in a population that had undergone three cycles of phenotypic selection for the same traits in order to extract breeding lines and for comparative analysis of gain from selection by phenotypic and marker-assisted selection (MAS). Frequencies of marker loci were used to monitor selection-dependent changes during phenotypic and MAS selection. Similar gain from selection was detected as a result of phenotypic and MAS selection for MLB (~0.3 branches/cycle), and L:D (~0.1 unit increase/cycle) with concomitant changes in frequency at linked marker loci. Although genetic gain was not realized for GYN during phenotypic selection, the percentage of female flowers of plants subjected to MAS increased (5.6 to 9.8% per cycle). MAS operated to fix favorable alleles that were not exploited by phenotypic selection. Empirical and molecular analyses of parthenocarpy in a different population indicate that this trait is under the control of several epistatic genes contributing small effects that are dramatically affected by growing environment. Thus, breeding strategies for the incorporation of parthenocarpy into commercial lines must be considered long-term and expensive.