1.1 Background to the Study
Pineapple (Ananas comosus) belongs to the bromeliaceace Family which contains 50 genera and about 2,500 known species. It is a tropical plant with an edible multiple fruit (Morton, 1987). Pineapple is an herbaceous perennial plant which grows to 1.0 to 1.5m (3.3 to 4.9ft) tall, although sometimes it can be taller. In appearance, the plant has a short, stocky stem with tough waxy leaves. When creating its fruit, it usually produces up to 200 flowers although some large fruited cultivars can exceed this. Once it flowers, the individual fruit of the flowers join together to create what is commonly referred to as pineapple.After the first fruit is produced, side shoots called suckers by commercial growers are produced in the leaf axils of the main stem. These may be removed for propagation or left to produce additional fruits on the original plant. In the first year of growth, the axis lengthens and thickens, bearing numerous leaves in close spirals. After 12 to 20months, the stems grows into a spike-like inflorescence up to 15cm long with over 100 spirally arranged, trimerous flowers, each subtended by a bract. The ovaries develop into berries, which coalesce into a large, compact multiple fruit. The fruit of a pineapple is arranged in two interlocking helices, eight in one direction, 13 in the other, each being a Fibonacci number. Pineapple carries out Crassulacean Acid Metabolism (C.A.M photosynthesis) fixing carbon dioxide at night and storing it as the acid malate, then releasing it during the day aiding photosynthesis.
Crop plant evolution either natural or human-directed, is primarily based on existing genetic diversity in the population. Diversity can be described as the degree of differentiation between or within species. Existing intra- and inter-specific differences are at the base of all crop improvement programmes. If all the individuals within the species would have been similar, then possibly there could not have been any scope for improvement in plant performances for different traits. Since the beginning of systematic plant breeding, natural variability and divergence between crops have been extensively identified and used in improvement of crop species.