Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/25/2006
Publication Date: 6/20/2006
Citation: Sun, Z., Lower, R.L., Staub, J.E. 2006. Variance component analysis of parthenocarpy in elite U.S. processing type cucumber (Cucumis sativus l.) lines. Euphytica. 148:333-341. Interpretive Summary: Parthenocarpic (seedless) U.S. processing type cucumber germplasm can bear more high quality fruit when compared to their seeded counterparts (standard commercial cucumber type that is pollinated and thereby produces seeds in the fruit). The inheritance (the genetic reason for the manifestation of this trait) of parthenocarpy in this market type is not fully understood, and thus understanding genetic components of variation would assist cucumber breeders when incorporating this economically important trait into commercial varieties. The inheritance of parthenocarpy in elite U.S. processing type cucumber was, therefore, investigated using unique breeding lines (highly uniform plant material). The data indicated that the inheritance of parthenocarpy in cucumber is controlled by 5 to 13 genes. This means that the inheritance of parthenocarpy is rather complex and that this trait will be hard to incorporate into commercial cucumber unless appropriate breeding strategies are implemented. This work suggests the use of some plant breeding strategies that will allow plant breeders to be more effective and efficient in breeding for parthenocarpic cucumber cultivars. Implementation of these strategies will result in the more rapid release of such cultivars. Parthenocarpic cucumber varieties will be higher yielding than the currently used standard cultivars that are not parthenocarpic. This increase in yield potential will increase the competitiveness of U.S. growers in the global market place.
Technical Abstract: Parthenocarpic (seedless) U.S. processing type cucumber (Cucumis sativus L.) germplasm can bear more high quality fruit when compared to their seeded counterparts. The inheritance of parthenocarpy in this market type is not fully understood, and thus understanding genetic components of variation would assist cucumber breeders when incorporating this economically important trait into commercial varieties. The inheritance of parthenocarpy in elite U.S. processing type cucumber was, therefore, investigated in F3 progeny derived from a mating between line 2A (P1, parthenocarpic) and line Gy8 (P2, non-parthenocarpic). A variance component analysis was applied to once-over harvest parthenocarpic yield data collected from F3 generation at two locations (E-block and G-block at Hancock, Wisc.) in the summer of 2000. There was a difference in the relative importance of additive genetic variance compared to dominance genetic variance across growing environments. The degree of dominance genetic variance was 0.3 and 2.2 at G-block and E-block, respectively. The minimum number of effective factors controlling parthenocarpy was estimated to be between 5 (G-block) to 13 (E-block). Moreover, estimations of heritability were significantly different when based on individual plants within an F3 family and on F3 family mean performances. While narrow-sense heritability of individual plants within F3 family ranged from 0.02 (E-block) to 0.07 (G-block), broad-sense heritability of individual plants within F3 family ranged from 0.07 (E-block) to 0.09 (G-block). The environmental variance accounted for about 90% of total phenotypic variance in both locations. In contrast, narrow-sense heritability estimates based on F3 family mean performance ranged between 0.33 (E-block) and 0.62 (G-block), and broad-sense heritability ranged between 0.53 (E-block) and 0.67 (G-block). These results suggest that, in this population, advanced generation selection for parthenocarpy based on F3 family mean performance will be more effective than selection of individual plants within F3 family.