Variance component analysis of parthenocarpy in elite U.S. processing type cucumber (Cucumis sativus L.) lines

Summary

Parthenocarpic (seedless) U.S. processing type cucumber (Cucumis sativus L.) germplasm can bear more high quality fruit when compared to their seeded counterparts. Knowledge of genetic components of variation for parthenocarpy would assist cucumber breeders to incorporate this economically important trait into commercial varieties. The inheritance of parthenocarpy in elite U.S. processing type cucumber was, therefore, investigated by examining the single-harvest yield of F₃ progeny derived from a mating between line 2A (P₁, parthenocarpic) and line Gy8 (P₂, non-parthenocarpic) grown in two fields (E-block and G-block at Hancock, Wisc.) in the summer of 2000. Environmental variance accounted for about 90% of total phenotypic variance in both locations. The degree of dominance genetic variance was 0.3 and 2.2 at G-block and E-block, respectively, and the minimum number of effective factors controlling parthenocarpy was estimated as 5 (G-block) to 13 (E-block). Estimates of heritability were significantly lower when based on individual plants within an F₃ family and on F₃ family mean performances. While narrow-sense and broad-sense heritability of individual plants within F₃ family was always < 0.1, narrow-sense heritability for 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). Thus, 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.