Little heterosis for yield and yield components in hybrids of six cucumber inbreds |
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| Authors: | Christopher S Cramer Todd C Wehner |
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| Institution: | (1) Department of Horticultural Science, North Carolina State University, Box 7609, Raleigh, NC, 27695-7609, U.S.A |
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| Abstract: | Heterosis and inbreeding depression for fruit yield has been reported for pickling cucumber (Cucumis sativus L.). However, cucumber inbreds often perform as well as hybrids, and there is little inbreeding depression. The objectives
of this study were to reexamine the amount of heterosis and inbreeding depression for fruit yield and yield components in
pickling cucumber, and to determine the relationship between yield components and yield for heterosis. Two pickling cucumber
inbreds (M 12, M 20) and inbreds from four open-pollinated monoecious cultivars (‘Addis’, ‘Clinton’, ‘Wisconsin SMR 18’, ‘Tiny
Dill’) were hybridized to form four F1 hybrids (‘Addis’ × M 20, ‘Addis’ × ‘Wis. SMR 18’, ‘Clinton’ × M 12, M 20 × ‘Tiny Dill’). F1 hybrids were then self-pollinated or backcrossed to generate F2, BC1A, and BC1B progeny. Thirty plants of each generation within each hybrid family were grown in plots 3.1 m long with four replications
in each of two seasons. Data were collected from once-over harvest for vegetative, reproductive, yield, and fruit quality
traits. Heterosis and inbreeding depression for fruit yield and yield components were not observed in three of the hybrids.
Only ‘Addis’ × ‘Wis. SMR 18’ exhibited high-parent heterosis and inbreeding depression for total, marketable, and early fruit
weight. For ‘Addis’ × ‘Wis. SMR 18’, heterosis for fruit yield was associated with a decreased correlation between percentage
of fruit set and fruit weight, an increased negative correlation between percentage of fruit set and both the number of branches
per plant and the percentage of pistillate nodes, and an increased negative correlation between the number of nodes per branch
and total fruit weight. Inbreeding depression was associated with a weakening of the strong negative correlations between
percentage of fruit set and the number of branches per plant, and between the number of nodes per branch and total fruit weight.
Those correlations were associated with high-parent heterosis and inbreeding depression only for one cross, and do not necessarily
apply to future crosses in which heterosis may be observed for yield. We did not observe the heterosis or inbreeding depression
for yield in cucumber in most of the crosses as was reported by Ghaderi & Lower (1979a; 1979c).
This revised version was published online in August 2006 with corrections to the Cover Date. |
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| Keywords: | combining ability correlation Cucurbitaceae Cucumis sativus earliness fruit shape inbreedingdepression quantitative genetics |
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