Papaya Biology, Cultivation, Production and Uses

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18

Descriptors

Papaya shows considerable phenotypic variation in morphological and horticultural
traits that can be utilised in its genetic improvement. On account of high degree of
variability in economic characters, several selections from the existing population
have been made in different papaya growing areas of the world. The objective of this
chapter was to provide information for collection, documentation and characterisa-
tion of the papaya germplasm. The wide diversity can be utilised for the selection
of promising parents in hybrid variety, inbred line development and estimating the
potential of genetic gain in a breeding programme. There is also need for proper
conservation of the different accessions reported as they could serve as raw mate-
rial for the genetic improvement of different characters of the crop through recur-
rent selection after hybridisation. Morphological and agronomical characterisation
is usually an affordable way to estimate the genetic diversity and is essential for
genotype discrimination and identification of duplicates. The morphological char-
acteristics were recorded and data from accessions submitted to principal compo-
nent and cluster analysis. The collected papaya germplasms were characterised in
the field using IBPGR (International Bureau of Plant Genetic Resources) morpho-
logical descriptors based on fruit, flower, stem and leaf characteristics. The lists
include accession data, collection data, site and plant data. Additional data to be col-
lected for further characterisation and evaluation of papaya are listed (site data, plant
data, stress susceptibility, pest and disease susceptibility, alloenzyme composition,
cytological characters and identified genes, and notes) below (IBPGR 1988).

18.1 Characterisation and Preliminary Evaluation

1. Site Data
   1.1 Country of characterisation and preliminary evaluation
   1.2 Site (research institute)
   1.3 Name of person(s) in charge of characterisation
   1.4 Sowing date
   1.5 Percentage germination
   1.6 Number of days to 50% germination
   1.7 Transplanting date
   1.8 Tree site in the field

Give block, strip and/or row numbers as applicable

1.9 Spacing in the field
1.10 Soil type

1. Clay


2. Clay-silt