Heterosis and Inbreeding Depression for Yield in Populations Derived from Six Crosses of Cucumber1

Abstract
Six crosses were made among eight cultivars and breeding lines of cucumber (Cucumis sativus L.). Within each cross 11 populations (including parents) representing 5 levels of heterozygosis were studied. Data were collected on fruit weight/plot, fruit number/plot, average fruit weight and fruit bearing index. Regression analysis was used to partition differences associated with levels of heterozygosis into linear, quadratic, and lack of fit components. With the exception of one cross, heterozygosis had significant positive effects on all characters. Linear responses of all populations to heterozygosis were highly significant for all characters in 5 of the 6 crosses. Incidences of significant quadratic and lack of fit mean squares were low. For all traits, with the exception of some instances of interallelic interactions, a genetic model based on cumulative action of independent loci with partial dominance explains differences associated with levels of heterozygosis.

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