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

Abstract

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 F 3 progeny derived from a mating between line 2A (P 1 , parthenocarpic) and line Gy8 (P 2 , 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 F 3 family than on F 3 family mean performances. While narrow-sense and broad-sense heritability of individual plants within F 3 family was always < 0.1, narrow-sense heritability for F 3 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 F 3 family mean performance will be more effective than selection of individual plants within F 3 family.

Identification and comparative analysis of quantitative trait loci associated with parthenocarpy in processing cucumber

“…parthenocarpy) using a one‐dimensional search (Doerge 2002). The epistatic interactions identified by two‐QTL model analysis performed herein are in agreement with an empirical assessment of F 3 families derived from a 2A × Gy8 mating (Sun et al. 2006a).…”

“…As no seeded fruit were observed during the random examination of fruit, all fruit were considered parthenocarpic. Although differences (P < 0.05) were detected between families and growing locations for parthenocarpic fruit number (G‐block > E block), family rank order differences between growing locations were negligible (Sun et al. 2006a).…”

“…The quantitative nature and expression of parthenocarpy is extremely complex (i.e. low heritability, epistasis and large genotype × environment interactions), and its incorporation requires complex phenotypic selection strategies (Sun et al. 2006a,b).…”

“…Parthenocarpy in cucumber under open‐field conditions is quantitatively controlled by at least two genes (Sun et al. 2006a,b).…”

Analysis of generation means and components of variance for parthenocarpy in cucumber (Cucumis sativus L.)

“…It is likely that the number of genes controlling parthenocarpy is more than one (greenhouse; 2A × Gy8 1999), two (open‐field; 2A × Gy8 2000), or four (open‐field; 2A × MM 2000) depending on the growing environment and population examined. Our estimates recapitulate those of Sun et al. (2006a)) obtained for the examination of F 3 families derived from the 2A × Gy8 population.…”