ABSTRACT
The papaya plant is a semi-woody, latex-producing, usually single-stemmed, shortlived perennial herb. The relatively small genome of this species shows peculiarities in major gene groups involved in the cell size and lignification, carbohydrate economy, photoperiodic responses and secondary metabolites, which place papaya in an intermediate position between herbs and trees (Ming et al. 2008). Reproductive precocity, high photosynthetic rates of short-lived leaves, fast growth, high reproductive output, production of many seeds and low construction cost of hollow stems, petioles and fruits characterise this successful tropical pioneer (Ming et al. 2008). High phenotypic plasticity allows this plant to establish in recently disturbed sites, thriving during early stages of tropical succession and as member of diverse agro-ecosystems as well (Ewel 1986), that constitute important genetic reservoirs (Brown et al. 2012). Under appropriate conditions of water availability, light, oxygen, air temperature and humidity, papaya seeds undergo epigeal germination; emergence is typically completed in 2-3 weeks (Fisher 1980). The papaya plant develops very fast, taking 3-8 months from seed germination to flowering (juvenile phase) and 9-15 months for harvest (Paterson et al. 2008). The plant can live up to 20 years; however, due to excessive plant height and pathological constraints, the commercial life of a papaya orchard is normally 2-3 years. At any given time, adult papaya plants can sustain vegetative growth, flowering and dozens of fruits at different stages of development simultaneously (Ming and Moore 2014).
