A. comosus is the most economically important plant in the family Bromeliaceae, which is divided into three subfamilies: Pitcarnioideae, Tillandsioideae and Bromelioideae. A. comosus belongs to the subfamily Bromelioideae, order Bromeliales, genus Ananas and species comosus (Bartholomew et al. 2003).
The family Bromeliaceae consists of approximately 2794 species and 56 genera that have adapted to a wide range of habitats ranging from terrestrial to epiphytic, shady to full sun and from hot humid tropics to cold dry subtropics. They can grow in moist to extremely dry situations and at varying altitudes from sea level to alpine conditions. (Bartholomew et al. 2003). Members of this family are characterised by a short stem, narrow stiff leaves arranged in a circular cluster, terminal inflorescences (racemes or panicles), hermaphroditic and actinomorphic trimerous flowers. Fruits are capsules or berries that contain small naked, winged or plumose seeds, with a reduced endosperm and a small embryo (Purseglove 1972; Bartholomew et al. 2003). The subfamily Bromelioideae, is the most diverse and consists of the largest number of genera but the lowest number of species. Most members are epiphytes characterised by a rosette like form, with spiny leaves and berry-like fruit containing wet seeds (Coppens d'Eeckenbrugge et al. 1997).
The genus Ananas is recognised among Bromeliaceae by the characteristic inflorescence, which is fused into a syncarp, a unique dense rosette of scape-wide leaves and medium to large fruits. Pineapple plants are set apart from other monocots by the characteristic star-shaped, scale-like multicellular hairs and unusual coiling stigmas, which fold together lengthwise (Gilmartin & Brown 1987). Cultivated pineapple was first described and named Karatas and Ananas at the end of the 17th century by Charles Plumier on the island of Hispaniola part of Antilles (West Indies) located between Cuba to the west and Puerto Rico to the east. Later all pineapples were classified in one genus, Ananas. Bartholomew et al (2003) stated that in 1892 Mez recognized in the Flora Brasiliensis only one species A. sativus and five botanical varieties. Pineapple taxonomy underwent further modification several times and it was not until 2003 that the classification developed by Coppens d’Eeckenbrugge and Leal (2003) was internationally adopted.
Based on similarity in floral structure, biology and chromosome number (2n=50), the current classification identifies six botanical varieties of A. comosus that intercross successfully with A. comosus var. comosus to produce fertile offsprings (Coppens d'Eeckenbrugge et al. 1997). The six varieties of A. comosus include the former species given below (Coppens d'Eeckenbrugge & Leal 2003):
- A. comosus var. ananassoides (formerly two species: A. ananassoides and A. nanus).
- A. comosus var. bracteatus (formerly two species: A. bracteatus and A. fritzmuelleri).
- A. comosus var. comosus (formerly A. comosus)
- A. comosus var. erectifolius (formerly A. lucidus (formely A. erectifolius)
- A. comosus var. parguazensis (formerly A. parguazensis)
- A. macrodontes (formerly Pseudananas sagenarius)
Ananas monstrous has been invalidated because the crownless fruit characteristic is not stable (Coppens d'Eeckenbrugge & Leal 2003). Generally, varieties of pineapple are distributed throughout the tropics and seed production is rare because most varieties of A. comosus possess reduced fertility combined with self-incompatibility (Coppens d'Eeckenbrugge et al. 1993).
There are approximately 30 cultivars of A. comosus that are grown commercially in tropical and sub tropical countries around the world. However, for convenience in global trade, the numerous pineapple cultivars are grouped in four main classes: ‘Smooth Cayenne’, ‘Red Spanish’, ‘Queen’ and ‘Pernambuco’ (Abacaxi), despite much variation in the types within each class (Morton 1987; Coppens d'Eeckenbrugge & Leal 2001). The fifth group or class comprising of ‘Motilona’ or ‘Perolera’ is commercially important in South America (Sanewski [& Scott 2000). In Australia the most dominant cultivar used in commercial plantations for canning purposes is Smooth Cayenne followed by Queen (Bartholomew et al. 2003).
Molecular markers are useful in establishing taxonomic relationships. F1 based genetic maps of DNA markers for A. comosus var. comosus and A. comosus var. bracteatus have been published. The map of var. comosus consists of 156 markers assembled in 30 linkage groups and covers over 31.6% of the genome; a dominant allele at locus P responsible for morphological traits ‘piping’, a silvery streak and the absence of spines along the margin of the upper leaf (Cabral et al. 1997) has been included in the latest map (Carlier 2004). The map of var. bracteatus gathers 335 DNA markers in 50 linkage groups and covers 57.2% of the genome length. Work is underway to complete the integrated genetic maps of these two varieties (Coppens d'Eeckenbrugge 2006).