Chemotaxonomic Considerations of the n‐Alkane Composition in Pinus heldreichii,P. nigra,and P. peuce

The n‐alkane composition in the leaf cuticular waxes of natural populations of Bosnian pine (Pinus heldreichii), Austrian pine (P. nigra), and Macedonian pine (P. peuce) was compared for the first time. The range of n‐alkanes was wider in P. nigra (C₁₆ – C₃₃) than in P. heldreichii and P. peuce (C₁₈ – C₃₃). Species also diverged in abundance and range of dominant n‐alkanes (P. heldreichii: C₂₃, C₂₇, and C₂₅; P. nigra: C₂₅, C₂₇, C₂₉, and C₂₃; P. peuce: C₂₉, C₂₅, C₂₇, and C₂₃). Multivariate statistical analyses (PCA, DA, and CA) generally pointed out separation of populations of P. nigra from populations of P. heldreichii and P. peuce (which were, to a greater or lesser extent, separated too). However, position of these species on the basis of n‐alkane composition was in accordance neither with infrageneric classification nor with recent molecular and terpene investigations.     

Chemodiversity of Nonacosan‐10‐ol and n‐Alkanes in the Needle Wax of Pinus heldreichii

This is the first report of individual variability and population diversity of the contents of nonacosan‐10‐ol and n‐alkanes in the needle cuticular waxes of Bosnian pines originated from Montenegro, regarded as Pinus heldreichii var. leucodermis, and from Serbia, regarded as P. heldreichii var. pan?i?i. The amount of nonacosan‐10‐ol varied individually from 27.4 to 73.2% (55.5% in average), but differences between the four investigated populations were not statistically confirmed. The size of the n‐alkanes ranged from C₁₈ to C₃₃. The most abundant n‐alkanes were C₂₃, C₂₇, and C₂₅ (12.2, 11.2, and 10.8% in average, resp.). The carbon preference index (CPI) of the n‐alkanes ranged from 0.8 to 3.1 (1.6 in average), while the average chain length (ACL) ranged from 20.9 to 26.5 (24.4 in average). Long‐chain and mid‐chain n‐alkanes prevailed (49.6 and 37.9% in average, resp.). It was also found that the populations of P. heldreichii var. leucodermis had predominantly a narrower range of n‐alkanes (C₁₈? C₃₁) than the trees of the variety pan?i?i (C₁₈? C₃₃). Differences between the varieties were also significant for most of the other characteristics of the n‐alkane pattern (e.g., most abundant n‐alkanes, CPI, ACL, and relative proportion of short‐, mid‐, and long‐chain n‐alkanes). The principle component and cluster analyses of eleven n‐alkanes confirmed the significant diversity of these two varieties.     

Population Variability of Nonacosan‐10‐ol and n‐Alkanes in Needle Cuticular Waxes of Macedonian Pine (Pinus peuce Griseb.)

This is the first report on population variability of nonacosan‐10‐ol and n‐alkanes in needle epicuticular waxes of Macedonian pine (Pinus peuce Griseb .) Hexane extracts of needle samples, originating from two natural populations in Montenegro (Zeletin and Sjekirica) and from one population in Serbia (Mokra Gora) were analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The amount of nonacosan‐10‐ol varied individually from 41.3 to 72.31% (average 55.9%), with the Sjekirica population being statistically divergent (64.4% on average). The results showed n‐alkanes in epicuticular waxes ranging from C₁₈ to C₃₃. The most abundant alkanes were C₂₉, C₂₅, C₂₇, and C₂₃ (15.5, 11.1, 10.6, and 10.5% on average, resp.). The carbon preference index of Pinus peuce ranged from 1.0 to 4.3 (1.9 on average). Average chain length ranged from 18.4 to 27.7 (average 25.7). A high level of inidividual quantitative variation in all of these hydrocarbon parameters was also detected. These results were compared with published data on other species from the Pinus genus.     

Variability of n‐Alkanes and Nonacosan‐10‐ol in Natural Populations of Picea omorika

This is the first report of population variability of the contents of n‐alkanes and nonacosan‐10‐ol in the needle epicuticular waxes of Serbian spruce (Picea omorika). The hexane extracts of needle samples originated from three natural populations in Serbia (Vranjak, Zmajeva?ki potok, and Mile?evka Canyon) were investigated by GC and GC/MS analyses. The amount of nonacosan‐10‐ol varied individually from 50.05 to 74.42% (65.74% in average), but the differences between the three investigated populations were not statistically confirmed. The results exhibited variability of the composition of n‐alkanes in the epicuticular waxes with their size ranging from C₁₈ to C₃₅. The most abundant n‐alkanes were C₂₉, C₃₁, and C₂₇ (35.22, 13.77, and 12.28% in average, resp.). The carbon preference index of all the n‐alkanes (CPI_total) of the P. omorika populations (average of populations I–III) ranged from 3.3 to 11.5 (mean of 5.9), while the average chain length (ACL) ranged from 26.6 to 29.2. The principal component and cluster analyses of the contents of nine n‐alkanes showed the greatest difference for the population growing in the Mile?evka Canyon. The obtained results were compared with previous literature data given for other Picea species, and this comparison was briefly discussed.     

Composition of n‐Alkanes in Natural Populations of Pinus nigra from Serbia – Chemotaxonomic Implications

This is the first report on the composition and variability of the needle‐wax n‐alkanes in natural populations of Pinus nigra in Serbia. Samples of 195 trees from seven populations belonging to several infraspecific taxa (ssp. nigra, var. gocensis, ssp. pallasiana, and var. banatica) were analyzed. In general, the size of the n‐alkanes ranged from C₁₆ to C₃₃, with the exception of ssp. nigra, for which it ranged from C₁₈ to C₃₃. The most abundant were C₂₃‐, C₂₅‐, C₂₇‐, and C₂₉‐alkanes. The needle waxes of Populations I–III and V were characterized by a higher content of C₂₃‐, C₂₅‐, and C₂₇‐alkanes and a lower content of C₂₄‐, C₂₆‐, C₂₈‐, and C₃₀‐alkanes, compared to the other populations, and the trees of these populations could be assigned to ssp. nigra. The samples of Population VI were characterized by higher amounts of C₂₂‐, C₂₄‐, C₃₀‐, and C₃₂‐alkanes and lower amounts of C₂₅‐ and C₂₇‐alkanes, and the trees could be considered as ssp. pallasiana. The samples of Population VII, consisting of trees belonging to var. banatica, were richer in C₂₉‐, C₃₁‐, and C₃₃‐alkanes. The wax compositions of Populations IV and V, both composed of trees previously determined as P. nigra var. gocensis, showed a tendency of splitting. Indeed, the alkane composition of Population IV was closer to that of ssp. pallasiana pines, while that of Population V was more similar to that of ssp. nigra pines. From the results presented here, it is obvious that in the central part of the Balkan Peninsula, significant diversification and differentiation of the populations of black pine exists, and these populations could be defined as different intraspecific taxa. Our results also indicate the validity of n‐alkanes as chemotaxonomic characters within this aggregate.     

Distribution and Variability of n‐Alkanes in Epicuticular Waxes of Sedum Species from the Central Balkan Peninsula: Chemotaxonomic Importance

For the first time, the n‐alkane distribution and variability of the epicuticular waxes within 22 Sedum taxa was reported with focus on the chemotaxonomy of native Sedum representatives from the central Balkan Peninsula, compared to their relations with four other species of the Crassulaceae family. By GC/MS and GC‐FID identification and quantification, it was established that n‐alkanes C₂₇, C₂₉, C₃₁, C₃₃, and C₃₅ were the dominant constituents of the examined epicuticular wax samples. Applying multivariate statistical analyses including agglomerative hierarchical clustering (AHC) and principal component analysis (PCA), the relation according to the n‐alkane composition between the examined samples was established. It was shown that the n‐alkane variability of the central Balkan Sedum species was considerable and that n‐alkanes might not be very reliable taxonomic markers for these species.     

Terpenes as Useful Markers in Differentiation of Natural Populations of Relict Pines Pinus heldreichii,P. nigra,and P. peuce

Comparative analysis of terpene diversity and differentiation of relict pines Pinus heldreichii, P. nigra, and P. peuce from the central Balkans was performed at the population level. Multivariate statistical analyses showed that the composition of needle terpenes reflects clear divergence among the pine species from different subgenera: P. peuce (subgenus Strobus) vs. P. nigra and P. heldreichii (subgenus Pinus). In addition, despite the described morphological similarities and the fact that P. nigra and P. heldreichii may spontaneously hybridize, our results indicated differentiation of their populations naturally growing in the same area. In accordance with recently proposed concept of ‘flavonic evolution’ in the genus Pinus, we assumed that the terpene profile of soft pine P. peuce, defined by high amounts of six monoterpenes, is more basal than those of hard pines P. nigra and P. heldreichii, which were characterized by high content levels of mainly sesquiterpenes. In order to establish precise positions of P. heldreichii, P. nigra and P. peuce within the taxonomic and phylogenetic tree, as well as develop suitable conservation strategies and future breeding efforts, it is necessary to perform additional morphological, biochemical, and genetic studies.     

Leaf n‐Alkanes as Characters Differentiating Coastal and Continental Juniperus deltoides Populations from the Balkan Peninsula

The composition of the cuticular n‐alkanes isolated from the leaves of nine populations of Juniperus deltoides R.P.Adams from continental and coastal areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 14 n‐alkane homologues with chain‐lengths ranging from C₂₂ to C₃₅ were identified. n‐Tritriacontane (C₃₃) was dominant in the waxes of all populations, but variations between the populations in the contents of all n‐alkanes were observed. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses) were used to investigate the diversity and variability of the cuticular‐leaf‐n‐alkane patterns of the nine J. deltoides populations. This is the first report on the n‐alkane composition for this species. The multivariate statistical analyses evidenced a high correlation of the leaf‐n‐alkane pattern with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon.     

Composition of Leaf n‐Alkanes in Three Satureja montana L. Subspecies from the Balkan Peninsula: Ecological and Taxonomic Aspects

The composition of the epicuticular leaf n‐alkanes of eight populations of three Satureja montana subspecies (S. montana L. subsp. pisidica (Wettst.) ?ili? , S. montana L. subsp. montana, and S. montana L. subsp. variegata (Host ) P. W. Ball ), from central and western areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 15 n‐alkane homologs with chain‐lengths ranging from C₂₁ to C₃₅ were identified. The main n‐alkane in almost all samples was n‐nonacosane (C₂₉), but differences in the contents of three other dominant n‐alkanes allowed separating the coastal from the continental populations. The diversity and variability of the epicuticular‐leaf‐n‐alkane patterns and their relation to different geographic and bioclimatic parameters were analyzed by several statistical methods (principal component, discriminant, and cluster analyses as well as the Mantel test). All tests showed a high correlation between the leaf n‐alkane pattern and the geographical distribution of the investigated populations, confirming the differentiation between S. montana subsp. pisidica and the other two subspecies. The S. montana subsp. variegata and S. montana subsp. montana populations are geographically closer and their differentiation according to the leaf‐n‐alkane patterns was not clear, even though there was some indication of discrimination between them. Moreover, most of the bioclimatic parameters related to temperature were highly correlated with the differentiation of the coastal and the continental populations.     

Biogeographic Variation of Foliar n‐Alkanes of Juniperus communis var. saxatilis Pallas from the Balkans

The composition of the epicuticular n‐alkanes isolated from the leaves of ten populations of Juniperus communis L. var. saxatilis Pallas from central (continental) and western (coastal) areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 14 n‐alkane homologues with chain‐lengths ranging from C₂₂ to C₃₅ were identified. All samples were dominated by n‐tritriacontane (C₃₃), but differences in two other dominant n‐alkanes allowed separating the coastal from the continental populations. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses as well as the Mantel test) were deployed to analyze the diversity and variability of the epicuticular‐leaf‐n‐alkane patterns of the ten natural populations of J. communis var. saxatilis and their relation to different geographic and bioclimatic parameters. Cluster analysis showed a high correlation of the leaf‐n‐alkane patterns with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon. Several bioclimatic parameters related to aridity were highly correlated with this differentiation.     

Geographically Related Variation in Epicuticular Wax Traits of Pinus nigra Populations from Southern Carpathians and Central Balkans – Taxonomic Considerations

The chemical composition of epicuticular waxes of nine populations from three Pinus nigra J. F. Arnold subspecies (namely subsp. nigra, subsp. banatica (Borbás ) Novák , and subsp. pallasiana (Lamb .) Holmboe ) from Southern Carpathians and central Balkan Peninsula were analyzed using GC/MS and GC/FID chromatography, and multivariate statistical techniques with respect to biogeography and taxonomy. In the needle waxes, four primary alcohols and 14 n‐alkanes ranging from C₂₁ to C₃₃ were identified, and the most abundant compounds were the four odd‐numbered n‐alkanes C₂₇, C₂₅, C₂₃, and C_29. Multivariate statistical analyses (CDA and CA) have shown existence of three P. nigra groups and suggested clinal differentiation as a mechanism of genetic variation across a geographic area: the first group consisted of the southernmost populations of subsp. pallasiana from Macedonia, the second consisted of the northernmost subsp. banatica populations from Romania, while all populations in Serbia described as three different subspecies (nigra, banatica, and pallasiana) formed the third group together with subsp. nigra population from Bosnia and Herzegovina. According to simple linear regression, geographic latitude and four bioclimatic parameters were moderately correlated with the contents of epicuticular wax compounds that are important in population discrimination, while stepwise multiple regression showed that latitude participated in most of the regression models for predicting the composition of the epicuticular waxes. These results agree with CDA and CA analysis, and confirmed the possibility of recognition of fine geographic differentiation of the analyzed P. nigra populations.     

Variations of the Composition of the Leaf Cuticular Wax among Chinese Populations of Plantago major

Plantago major L. grows in a very wide range of regions in China and exhibits great variations among populations. The analysis of the cuticular‐wax composition provides a potential approach to classify populations of P. major confronting different environmental conditions. Twelve populations of P. major and five populations of P. depressa Willd ., distributed over regions with average annual temperatures ranging from ?2.0 to 18.4°, were sampled, the variation of the composition of their cuticular waxes was analyzed, and their values of average chain length (ACL) and carbon preference index (CPI) were calculated. Great intra‐ and interspecies variations were observed for the total wax contents. The average annual temperature of the habitats was significantly correlated with the relative contents of the dominant n‐alkanes with an odd number of C‐atoms, but not with the wax contents. With an increasing average annual temperature, the relative contents of n‐alkanes C₂₉ and C₃₁ decreased, whereas those of C₃₃ and C₃₅ as well as the values of ACL_total and ACL_27–33 increased. Cluster analysis based on the pattern of the n‐alkane distribution allowed to clearly separate the populations of P. major according to the average annual temperature of their habitats, but not to separate the populations of the two species. Hence, the pattern of the n‐alkane distribution might be a good taxonomic marker for P. major at the intraspecies level, but not at the interspecies level. Nevertheless, a small difference between the populations of the two species was observed concerning the values of ACL_total and CPI_total, implying the potential use of these indices for the classification of the populations of the two species at the interspecies level.     

Application of Two‐Way Hierarchical Cluster Analysis for the Identification of Similarities between the Individual Lipid Fractions of Lucilia sericata

The composition of the cuticular and internal lipids of larvae and pupae of Lucilia sericata was studied using chromatographic techniques. The lipids from both stages of L. sericata had similar free fatty acid (FFA) profiles and also contained alcohols and cholesterol. The range of the number of C‐atoms detected for these classes of compounds was to some extent similar in larvae and pupae, but the relative amounts of each class differed between stages. Saturated as well as unsaturated FFAs with even and odd numbered C‐atom chains were present in both cuticular and internal lipids. The alcohol fractions of L. sericata were represented by free, straight‐chain primary alcohols containing an even number of C‐atoms. The lipid composition of male and female L. sericata adults and the hydrocarbon composition of all stages of L. sericata had previously been analyzed. To have a full overview of the lipid composition and to identify similarities or dissimilarities between the individual lipid fractions in this insect species, two‐way hierarchical cluster analysis (HCA) was performed using also the data from these previous publications. The content of FFA 18 : 1 (n‐9) was noticed to be very high in the cuticular fractions of larvae and pupae as well as in all internal fractions (male, female, larvae, and pupae) and low in the cuticular fractions of male and female imago. The contents of FFAs 16 : 0 and 16 : 1 (n‐9), cholesterol, and the n‐alkanes n‐C₃₁, n‐C₂₉, n‐C₂₇, n‐C₂₅, and n‐C₂₃ varied between particular fractions, whereas the amounts of other compounds were similar in all fractions.     

Leaf wax n‐alkane patterns of six tropical montane tree species show species‐specific environmental response

It remains poorly understood how the composition of leaf wax n‐alkanes reflects the local environment. This knowledge gap inhibits the interpretation of plant responses to the environment at the community level and, by extension, inhibits the applicability of n‐alkane patterns as a proxy for past environments. Here, we studied the n‐alkane patterns of five Miconia species and one Guarea species, in the Ecuadorian Andes (653–3,507 m a.s.l.). We tested for species‐specific responses in the average chain length (ACL), the C₃₁/(C₃₁ + C₂₉) ratio (ratio), and individual odd n‐alkane chain lengths across an altitudinally driven environmental gradient (mean annual temperature, mean annual relative air humidity, and mean annual precipitation). We found significant correlations between the environmental gradients and species‐specific ACL and ratio, but with varying magnitude and direction. We found that the n‐alkane patterns are species‐specific at the individual chain length level, which could explain the high variance in metrics like ACL and ratio. Although we find species‐specific sensitivity and responses in leaf n‐alkanes, we also find a general decrease in “shorter” (<C₂₉) and an increase in “longer” (>C₃₁) chain lengths with the environmental gradients, most strongly with temperature, suggesting n‐alkanes are useful for reconstructing past environments.     

Arabidopsis ketoacyl‐CoA synthase 16 (KCS16) forms C36/C38 acyl precursors for leaf trichome and pavement surface wax

The aliphatic waxes sealing plant surfaces against environmental stress are generated by fatty acid elongase complexes, each containing a β‐ketoacyl‐CoA synthase (KCS) enzyme that catalyses a crucial condensation forming a new C─C bond to extend the carbon backbone. The relatively high abundance of C₃₅ and C₃₇ alkanes derived from C₃₆ and C₃₈ acyl‐CoAs in Arabidopsis leaf trichomes (relative to other epidermis cells) suggests differences in the elongation machineries of different epidermis cell types, possibly involving KCS16, a condensing enzyme expressed preferentially in trichomes. Here, KCS16 was found expressed primarily in Arabidopsis rosette leaves, flowers and siliques, and the corresponding protein was localized to the endoplasmic reticulum. The cuticular waxes on young leaves and isolated leaf trichomes of ksc16 loss‐of‐function mutants were depleted of C₃₅ and C₃₇ alkanes and alkenes, whereas expression of Arabidopsis KCS16 in yeast and ectopic overexpression in Arabidopsis resulted in accumulation of C₃₆ and C₃₈ fatty acid products. Taken together, our results show that KCS16 is the sole enzyme catalysing the elongation of C₃₄ to C₃₈ acyl‐CoAs in Arabidopsis leaf trichomes and that it contributes to the formation of extra‐long compounds in adjacent pavement cells.     

Lipophilic Metabolites from Five‐Needle Pines,Pinus armandii and Pinus kwangtungensis,Exhibiting Antibacterial Activity

Lipophilic extractive metabolites from needles and defoliated twigs of Pinus armandii and P. kwangtungensis were studied by GC/MS. Needles of P. armandii contained predominantly 15‐O‐functionalized labdane type acids (anticopalic acid), fatty acids, nonacosan‐10‐ol, sterols, nonacosan‐10‐ol and sterol saponifiable esters, and acylglycerols, while P. kwangtungensis needles contained no anticopalic acid, but more trinorlabdane (14,15,16‐trinor‐8(17)‐labdene‐13,19‐dioic acid) and other labdane type acids, nonacosan‐10‐ol and its saponifiable esters. The major compounds in the P. armandii defoliated twig extract were abietane and isopimarane type acids, fatty acids, sterols, labdanoids (cis‐abienol), cembranoids (isocembrol and 4‐epi‐isocembrol), saponifiable sterol esters, and acylglycerols. The same extract of P. kwangtungensis contained larger quantities of fatty acids, caryophyllene oxide, serratanoids, sterols, saponifiable sterol esters, and acylglycerols, but lesser amounts of abietane and isopimarane type acids, cis‐abienol, and lacked cembranoids. Both twig and needle extracts of P. armandii and P. kwangtungensis, as well as the extracts’ fractions, significantly inhibited the growth of Gram‐negative bacteria Serratia marcescens with MIC of 0.1 mg ml^?1, while in most cases they slightly stimulated the growth of Gram‐positive bacteria Bacillus subtilis at the same concentrations. Thus, lipophilic extractive compounds from the needles and defoliated twigs of both pines are prospective for the development of antiseptics against Gram‐negative bacteria.     

Compositae Plants Differed in Leaf Cuticular Waxes between High and Low Altitudes

We sampled eight Compositae species at high altitude (3482 m) and seven species at low altitude (220 m), analyzed the chemical compositions and contents of leaf cuticular wax, and calculated the values of average chain length (ACL), carbon preference index (CPI), dispersion (d), dispersion/weighted mean chain length (d/N), and C₃₁/(C₃₁ + C₂₉) (Norm31). The amounts of total wax and compositions were significantly higher at high altitude than at low altitude, except for primary alcohol, secondary alcohol, and ketone. The main n‐alkanes in most samples were C₃₁, C₂₉, and C₃₃. Low altitude had more C₃₁ and C₃₃, whereas more C₂₉ occurred at high altitude. The ACL, CPI, d, d/N, and Norma 31 were higher at low altitude than at high altitude. The fatty acid and primary alcohol at low altitude contained more C₂₆ homologous than at high altitude. More short‐chain primary alcohols were observed at high altitude. At low altitude, the primary alcohol gave on average the largest amount, while it was n‐alkane at high altitude. These results indicated that the variations of leaf cuticular waxes benefited Compositae plants to adapt to various environmental stresses and enlarge their distribution.     

Surface wax of Andreaea and Pogonatum species

The mosses Andreaea rupestris, Pogonatum aloides and P. urnigerum contain surface waxes in amounts of 0.05–0.12% dry wt. The waxes consisted of esters (C₃₈-C₅₄), primary alcohols (C₂₀-C₃₂), free fatty acids (C₁₆-C₃₀), and alkanes (C₂₁-C₃₁). Additionally, aldehydes (C₂₂-C₃₀) were major constituents in the wax of P. urnigerum. The classes and their chain length distributions in the surface waxes of these mosses are comparable to those of epicuticular waxes of higher plants.     

Climate signal in tree-ring chronologies of Pinus peuce and Pinus heldreichii from the Pirin Mountains in Bulgaria

Numerous proxy climate reconstructions have been developed for Europe, but there are still regions with limited data of this kind. One region is the Balkan Peninsula, which is characterized by complex interactions between mountains and climate. We present and discuss two tree-ring chronologies—a 758-year-long one of Pinus heldreichii Christ and 340-year-long one of Pinus peuce Griseb. from treeline locations in the Pirin Mountains in Bulgaria. Climate–growth relationships were computed with bootstrap correlation functions and their consistency over time assessed by calculating the correlations over shortened periods. In addition, we reviewed and analyzed climate situations in years with unusually narrow or wide tree rings. Both species were negatively influenced by previous summer drought conditions and cold winters. Early summer temperatures were positively correlated with P. peuce radial growth, whereas P. heldreichii displayed dependence on summer precipitation. In the second half of the twentieth century, the P. heldreichii trees displayed higher sensitivity to summer drought, which was probably a result of increased summer temperatures and decreased winter precipitation. Our findings contribute to more reliable proxy climate records for the region.     

The Inhibitor of wax 1 locus (Iw1) prevents formation of β‐ and OH‐β‐diketones in wheat cuticular waxes and maps to a sub‐cM interval on chromosome arm 2BS

Glaucousness is described as the scattering effect of visible light from wax deposited on the cuticle of plant aerial organs. In wheat, two dominant genes lead to non‐glaucous phenotypes: Inhibitor of wax 1 (Iw1) and Iw2. The molecular mechanisms and the exact extent (beyond visual assessment) by which these genes affect the composition and quantity of cuticular wax is unclear. To describe the Iw1 locus we used a genetic approach with detailed biochemical characterization of wax compounds. Using synteny and a large number of F₂ gametes, Iw1 was fine‐mapped to a sub‐cM genetic interval on wheat chromosome arm 2BS, which includes a single collinear gene from the corresponding Brachypodium and rice physical maps. The major components of flag leaf and peduncle cuticular waxes included primary alcohols, β‐diketones and n‐alkanes. Small amounts of C19–C27 alkyl and methylalkylresorcinols that have not previously been described in wheat waxes were identified. Using six pairs of BC₂F₃ near‐isogenic lines, we show that Iw1 inhibits the formation of β‐ and hydroxy‐β‐diketones in the peduncle and flag leaf blade cuticles. This inhibitory effect is independent of genetic background or tissue, and is accompanied by minor but consistent increases in n‐alkanes and C₂₄ primary alcohols. No differences were found in cuticle thickness and carbon isotope discrimination in near‐isogenic lines differing at Iw1.