Location: Forage and Range ResearchTitle: Response to Phenotypic and Marker-Assisted Selection for Yield and Quality Component Traits in Cucumber (Cucumis Sativus L.)) Author
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2009
Publication Date: 3/15/2010
Citation: Behera, T.K., Staub, J.E., Behera, S., Mason, S. 2010. Response to Phenotypic and Marker-Assisted Selection for Yield and Quality Component Traits in Cucumber (Cucumis Sativus L.). Euphytica. 171:417-425. Interpretive Summary: Certain genetic tools related to the evolving field of biotechnology (use of new and novel technologies which incorporate DNA) can be important to plant improvement. Plant improvement can be enhanced by biotechnology by allowing for superior plants to be identified more rapidly with reduced cost inputs (i.e., expensive and extended field testing of plants in the early generations of plant improvement). One biotechnology that has been advocated but not rigorously tested is "marker-assisted selection" (MAS) which involves the extraction of DNA from plant cells and then visualizing differences (profiles) in DNA between plants using biochemical techniques (i.e., polymerase chain reactions). In the case of cucumber, MAS has not been rigorously evaluated to determine whether it would increase the efficiency of plant breeding for the development of superior cultivars. Thus, an experiment was designed to evaluate MAS during plant improvement of unique cucumber plants that underwent repeated selection for improved DNA profile characteristics. DNA was extracted from plants at each of three generations of selection (i.e., for the best DNA profiles). It was determined that MAS was effective in improving plant performance for fruit yield and quality in early but not in later generations of selection. The general effect of applying MAS for cucumber improvement was positive. The data obtained in this study will allow commercial and private plant breeders to use DNA biotechnology of MAS more effectively for plant improvement. This is important for the grower since new and novel cucumber varieties will be available to them more rapidly, thus increasing their global competitiveness.
Technical Abstract: Even though the potential benefits of marker-assisted selection (MAS) for line and population development to improve yield in cucumber have been demonstrated, its application during tandem selection for yield and quality components has not been investigated. Therefore, two cucumber recombinant inbred lines (RILs) differing in plant habit were crossed and progeny self-pollinated to produce F3 individuals upon which phenotypic selection (PHE) was practiced to identify a base population (BASE) which in turn underwent either two cycles of MAS (genotyping at 12 marker loci) or random mating without selection (RAN). Four test arrays were constructed from BASE F3 progeny that exhibited differing fruit yield (fruits/plant) and quality [fruit length:diameter ratio (L:D) and interior (endocarp) seed cavity size (E:T)] under replicated open-field conditions. MAS and RAN were practiced on these test arrays [low yield and low quality (i.e., low L:D and high E:T), low yield and high quality, high yield and low quality, and high yield and high quality] to produce F4 and F5 progeny sets. Original RIL, crossing parents, and F3-F5 progeny sets were then evaluated under replicated field conditions at one location for fruit yield and quality (L:D, and E:T) to evaluate gain from selection ( G). The broad-sense heritability (h2B) over cycles (C) of selection ranged from 0.22 to 0.45, 0.09 to 0.20, and 0.11 to 0.15 for yield, L:D, and E:T, respectively. The correlation coefficients between the traits examined were low (0.06-0.08) to moderate (0.40-0.46). Although one cycle of PHE selection followed by MAS was effective in conserving the performance of the traits examined during inbreeding, progeny performance during RAN fluctuated (F4 to F5 generation; C2). Lack of G during advanced generations (F4-F5) of MAS was likely due to allelic fixation and/or optimized epistatic complementation.