RIND AND LEAF OILS OF TRIPLOID INTERSPECIFIC CITRUS HYBRIDS AND THEIR DIPLOID AND TETRAPLOID PARENTS

Abstract

SummaryRind and leaf oils of triploid Citrus hybrids from 5 crosses, and their diploid and tetraploid parents, were analysed by gas chromatography. Two‐thirds of the chromosome complement of each hybrid was evidently contributed by the 4n parent. Overall, a wide range of percentages of the oil components occurred among hybrids and parents. There were differences significant at 1% in 80 of 90 parent‐hybrid group comparisons. There was no regular, dominating effect of the 4n parents, and in many cases the influence of 4n and 2n parents seemed about equal. However, among hybrids involving 4n lemon there was often a tendency for leaf oil levels to follow those of that 4n parent. The general absence of such an effect in the rind oils, and in the leaf oils of the other crosses, parallels the implication of an earlier study in which autotetraploids of several Citrus species were usually similar to their parental diploids, in their percentages of rind oil components.Where 2 or 3 sets of hybrids had a common parent, either 2n or 4n, there was also no constant effect of that parent, from set to set, as compared to other parents involved. Variation in the percentages of any specific oil component was great among the 6 sister triploids in many crosses. Individuals sometimes approached the level of one parent, and sometimes that of the other. Transgression of one or more hybrids beyond either parent frequently occurred, and was particularly prominent with decanal, linalool, and linalyl acetate. Percentages of components in the leaf were often different from those in the rind.It is clear that these polyploid hybrids of rather closely related species show many inherited differences in oil components. These differences are principally quantitative and probably reflect genetic recombinations which have altered intermediate biochemical pathways.