Symrise GmbH & Co
Holzminden, Germany
Fabienne Lapeyre-Montes
Unité Mixte de Recherche—Développement et Amélioration
Centre de Recherche Agronomique Pour le Développement
Montpellier, France
Sandra Lepers-Andrzejewski
Département Recherche et Développement
Etablissement Vanille de Tahiti
Uturoa, Raiatea, French Polynesia
Kenny Le Roux
Unité Mixte de Recherche—Peuplement Végétaux et Bioagresseurs en Milieu Tropical
Centre de Recherche Agronomique Pour le Développement
Saint Pierre, La Réunion, France
Edward C.Y. Liew
Royal Botanic Gardens Sydney
Botanic Gardens Trust
Sydney, New South Wales, Australia
Gerd Lösing
Symrise GmbH & Co
Holzminden, Germany
Pesach Lubinsky
Department of Botany and Plant Sciences
University of California
Riverside, California
Raoul Lucas
Faculté des Lettres et Sciences
Humaines Université de la Réunion
Saint Denis, La Réunion, France
Eric Odoux
Unité Mixte de Recherche—Qualisud
Centre de Recherche Agronomique Pour le Développement
Montpellier, France
Michael Pearson
School of Biological Sciences
The University of Auckland
Auckland, New Zealand
Marc Pignal
Unité Mixte de Recherche—Origine, Structure et Evolution de la Biodiversité
Muséum National d’Histoire Naturelle
Paris, France
Serge Quilici
Unité Mixte de Recherche—Peuplement Végétaux et Bioagresseurs en Milieu Tropical
Centre de Recherche Agronomique Pour le Développement
Saint Pierre, La Réunion, France
Patricia Rain
The Vanilla Company
Santa Cruz, California
Agathe Richard
Unité Mixte de Recherche—Peuplement Végétaux et Bioagresseurs en Milieu Tropical
Centre de Recherche Agronomique Pour le Développement
Saint Pierre, La Réunion, France
Michel Roux-Cuvelier
Unité Mixte de Recherche—Peuplement Végétaux et Bioagresseurs en Milieu Tropical
Centre de Recherche Agronomique Pour le Développement
Saint Pierre, La Réunion, France
Y.R. Sarma
Indian Institute of Spices Research
Calicut, Kerala, India
Samira Sarter
Unité Mixte de Recherche—Qualisud
Centre de Recherche Agronomique Pour le Développement
Antananarivo, Madagascar
B. Sasikumar
Indian Institute of Spices Research
Calicut, Kerala, India
Joseph Thomas
Indian Cardamom Research Institute
Spice Board
Idukki, Kerala, India
Mesak Tombe
Entomology and Phytopathology Divison
Indonesian Medicinal and Aromatic Crops Research Institute
Bogor, Indonesia
S. Varadarasan
Indian Cardamom Research Institute
Spice Board
Idukki, Kerala, India
Jean-Luc Verdeil
Unité Mixte de Recherche—Développement et Amélioration
Centre de Recherche Agronomique Pour le Développement
Montpellier, France
Hongyu Wang
The National Center for Agricultural
Biodiversity Research and Development Yunnan Agricultural University
Kunming, China
Yunyue Wang
The National Center for Agricultural Biodiversity Research and Development
Yunnan Agricultural University
Kunming, China
Xurui
Flavors and Fragrances Research Institute
Yunnan Agricultural University
Kunming, China
Robber Zaubin
Eco-Physiology Division
Indonesian Medicinal and Aromatic Crops Research Institute
Bogor, Indonesia
Hengcang Zhou
Flavors and Fragrances Research Institute
Yunnan Agricultural University
Kunming, China
Chapter 1. Vanilloid Orchids
Systematics and Evolution
Kenneth M. Cameron
Introduction
Vanilla and its relatives are surviving members of what is likely an ancient lineage of flowering plants. Many are restricted to remote localities, and some are threatened with extinction. We certainly know a great deal about Vanilla planifolia—methods of cultivation, diseases that affect the domesticated vines, and techniques of fruit processing—but the fundamental natural history of the entire genus Vanilla and its closest relatives is still poorly known. The systematic study of these plants has been and continues to be surrounded by controversies. For these reasons it is encouraging to witness the increased level of knowledge in recent years regarding their classification and evolution, which has come about primarily thanks to the increased use of DNA-based data in systematic studies (e.g., see Cameron, 2003, 2004, 2006).
Until the end of the twentieth century, the vanilloid orchids had proven difficult to classify within any particular subtribe, tribe, or subfamily of the family Orchidaceae. On the one hand, they share the presence of a fully bent, single, fertile anther with various advanced orchid lineages. On the other hand, they exhibit a variety of characters considered primitive among orchids. Botanists now consider the single fertile anther at the apex of the vanilla flower’s column to have risen by way of a different evolutionary process than that of nearly all other orchids (i.e., those classified within the Epidendroideae and Orchidoideae subfamilies). For this reason and others mentioned below, vanilla and related orchids are now classified within their own unique subfamily, Vanilloideae, as shown in Figure 1.1.
FIGURE 1.1 Cladogram depicting the phylogenetic relationships among subfamilies of Orchidaceae and among genera within Vanilloideae based on a combination of nuclear, mitochondrial, and plastid DNA sequence data. The subfamily is divided into two tribes: Pogonieae and Vanilleae. Note that Vanilla shares a common ancestor with a clade of four genera including Galeola and Pseudovanilla.
As we move further into the twenty-first century and the genomics era, there is little doubt that plant breeders will endeavor to improve vanilla as a crop plant using genetic modification. Any future genetic studies into the structure and development of the vanilla flower and/or fruit should consider looking closely at other genera of Vanilloideae with shared ancestry, rather than making direct comparisons only to more distantly related orchids or other flowering plants. Such comparisons could be misleading in their assumptions of homology. This point is best appreciated by considering that over the course of more than 65 million years, vanilloid orchids have become adapted to a variety of specialized habitats, pollinators, and seed-dispersal strategies. They all share a fundamental genome in common, based on a now extinct ancestor, and yet differences in gene expression and regulation ultimately determine whether a given vanilloid orchid grows in the tropics or survives temperatures well below freezing, whether it grows as an erect herb or as a vine, and whether it will produce a dry flavorless capsule or an aromatic fleshy fruit. As genomic and proteomic technology is eventually applied to crop plants of lesser economic value (compared to cereals and legumes, for example) studies targeting the improvement of vanilla may also wish to consider other genera of tribe Vanilleae or subfamily Vanilloideae. For example, it might be possible to develop more cold- and shade-tolerant vanilla vines by first studying the physiology and genetic makeup of Cyrtosia, a close relative that survives in the deciduous forests of Japan and China. On the basis of these arguments, a review of vanilloid orchid systematics (the scientific study of the diversity and classification of organisms) is presented here in order to set the stage for a more comprehensive understanding of the biology of V. planifolia and these exceptional orchids.