Geographic variation in the leaf oils and DNA fingerprints (RAPDs) of Juniperus thurifera L. from Morocco and Europe

Journal of Essential Oil Research: JEOR, May/Jun 2003 by Adams, Robert P, Mumba, Luke E, James, Shelley A, Pandey, Ram Naresh, Et al

Abstract

Samples of Juniperus thurifera L. were collected from the Atlas Mts., Morocco, northern and southern Spain, the Pyrenees, France, Fench Alps and Corse Isaland, France. The leaf oils were analyzed and found to he polymorphic for several major compounds (sabinene, limonene, linalool, piperitone, linalyl acetate and sesquiterpenes). In general, the Moroccan trees were higher in sabinene, gamma-terpinene, cis-sabinene hydrate and terpinen-4-ol, but lower in limonene, delta-2-carene, and piperitone than trees from Europe. Analysis based on Random Amplified Polymorphic DNAs (RAPDs) for the aforementioned population plus J. foetidissima (as an outgroup), revealed that the Moroccan J. thurifera populations were most similar to plants from southern Spain, then to populations from France. Although the trees generally clustered by populations, there appear to be some differentiation in the RAPDs between the European J. thurifera populations and the Moroccan populations. Combining previous studies on seeds per cone, proanthrocyanidins, and the current report on the leaf essential oils and RAPDs, there is some support for the continued recognition of J. thurifera var. africana Maire [syn.: J. African.a (Maire); J. thurifera ssp. africana (Maire) Gauquelin, Hassani et Lebreton] in Algeria and Morocco.

Key Word Index

Juniperus thurifera, Cupressaceae, composition of essential oil, RAPD, DNA fingerprinting, systematics.

Introduction

The genus Juniperus consists of approximately 67 species and 26 varieties, using the more widely accepted variety category instead of the subspecies category (1). All the taxa grow on the Laurasian land mass, except J. procera Hochst. ex Endl., which grows along the rift mountains in East Africa into the southern hemisphere (2) and some of the Mediterranean Juniperus species such asj. oxycedrus L.,J. phoenicea L., and J. thurifera L. that grow in the mountains of the northernmost part of Africa (Morocco, Algeria).

The genus is divided (3) into three sections: Caryocedrus (one species, J. drrupacea Labill.); Juniperus (= Oxycedrus) with 12-13 species, and Sabina, the remaining, with approximately 50 species. A previous study using RAPDs (3) indicated that section of Sabina could be further divided into junipers with serrate and those with entire (smooth) leaf margins. The serrate leaf margined junipers are confined to the western hemisphere, although Gaussen (4) scored several eastern hemisphere species as having leaves with serrate margins. Gaussen (4) followed the classical treatment in dividing the genus into three sub-genera (sections)-- Caryocedrus, Oxycedrus (=Juniperus by nomenclatural convention) and Sabina-and her further divided Sabina into two series: denticulees (denticulate) and entires (entire) leafed species. Gaussen (4) even subdivided these series into sections. The section phoenicioides was put in the class with serrate leaf margins (4). However, the leaves of all the taxa listed in Gaussen's treatment (4, p. 81) have entire leaf margins at 40 X (RPA). Furthermore, DNA evidence shows that Gaussen's phoenicioides is not related to the serrate junipers of the western hemisphere (3).

The Juniperus of section Sabina, of the eastern hemisphere can be further divided into two groups based on the number of seeds per female cone (often called berry) and female cone shape. The single seed/cone (single seeded) Juniperus of the eastern hemisphere have cones that are ovoid with a noticeable pointed tip, whereas the multi-seeded Juniperus are generally round and often have an irregular surface. Based on DNA fingerprinting data (RAPDs), Adams (1) found that J. thurifera (from Spain) is loosely associated with J. foetidis.sina Willd. and in turn with J. polycarpos K. Koch and J. excelsa M.-Bieb.

Juniperus thurifera from North Africa has been the subject of several nomenclatural changes having been treated as a variety U. thurifera var. africana Maire, Bull. Soc. Hist. Nat. Afrique N. 17:125(1926)], then as a distinct species [U. africana (Maire) Villar, Types Sols Afrique N. 1:91 (1947)].

More recently, a study (5) using proanthrocyanidins and the number of seeds per cone, resulted in the naming of a new subspecies [J. thurifera ssp. africana (Maire) Gauquelin, Hassani et Lebreton] and three chemivars (hispanica, Spain; gallica, France; and Coriscana, Corse-Firgure 1). They found (5) that the number of seeds per cone was significantly smaller (1.21 seeds/cone) in Morocco than in Europe where the number of seeds/cone ranged from 2.9-3.1 (Figure 2). Barbero et al. (6) reported additional morphological measurements that seemed to support the recognition of the subspecies. Barbero et al. (6) discussed the chemivars as varieties, but they did not appear to actually name the chemivars as varieties in a nomenclatural sense. In a recent treatment of the conifers, Farjon (7) recognized J. thurifera and treated J. africana and J. thurifera var. africana as synonyms. There have been several reports on the oils of J. thurifera. Teresa et al. (8) found the berry oil of J. thurifera to be dominated by limonene (88.5%). San Feliciano et al. (9) reported a number of sesquiterpenes and diterpenes from the leaf oil of J. thurifera. Akimov et al. (10) found the leaf oil of J. thurifera to have small amounts of monoterpenes (