Results and Discussion

The n-alkane compositions of the waxes of Chinese Spring and of the 29 ditelosomic lines are shown in Table 1.

Although, as found previously by several authors, the dominant homologue chains are the common C₂₇, C₂₉, and C₃₁, the data obtained allow to gather the lines studied in three groups according to the distribution on n-alkanes. The first group whose n-alkane distribution is shown in Figure 1 (A), comprises the Chinese Spring and 24 ditelosomic lines. The spectrum describing the per cent composition in n-alkane homologues is typical ; that is C₂₇, C₂₉ and C₃₁ predominate and only a 1.4% of n-octacosane with traces of other even number homologues are present.

In the case of Chinese Spring n-alkanes also a small amount of short chain homologues, namely C₁₄ (0.4%), C₁₆ (3.7%), C₁₈ (2.2%), C₂₀ (0.9%) was found. Although traces of n-alkanes with chain lengths in this range are frequently detected in waxes of several plants, two points are of relevance : first the relatively high percentage of these homologues, second the even number chains.

The second group comprising 1B-S, 2B-L, 6B-L and 7B-L shows a significant increase in even carbon chains which, in fact, reaches an averaged value of 6.0% of the total (Figure 1 (B)).

Figure 1 (C) shows the very unusual distribution of chain lengths composing the n-alkanes of 7A-L wax. The percentage of even number carbon chains is exceptionally high (24.1%) for this cereal and in sharp contrast with the composition of the other lines analyzed.

Apart from the relevant biochemical aspects regarding the biosynthesis of alkanes which will be discussed in a forthcoming paper (BIANCHI et, al.) we believe that the present approach is the most promising in order to obtain information on the genetical control of the wax production. It seems very promising to be able to associate the absence of an arm of the chromosome with chemical composition, class by class, of wax and distribution of homologous chains within each class of compounds.

At this preliminary stage of our research it appears evident the superior validity of this approach compared with simple visual observations. The latter approach, in fact, could have failed in distinguishing between almost all the lines studied here. The chemical analyses, although limited to the alkanes, allow to relate the presence of well defined effect, at chemical composition level, with certain chromosomes.

Thus, the phenotypic characters, glaucousness-non glaucousness (waxiness-waxless or more precisely scarcity in wax production) are explained in terms of wax chemical composition.