24 Papaya
Teratological staminate flowers are produced by sex-reversing males. Depending
upon the variations in environmental conditions, sex-reversing males can produce
all the eight types of flowers. However, the hermaphrodite plants can have six types,
except staminate and teratological staminate flowers. The female plants normally
bear pistillate flowers, though rarely they can produce bisexual flowers (Ram 1996).
Generally, the change in sex of male plants is towards hermaphroditism or female-
ness. Hermaphrodite plants, however, do not produce staminate flowers. Similarly,
female plants never undergo any change with regard to sex forms and, thus, never
found to possess any hermaphrodite or male flowers. Femaleness is the most stable
character, least affected by seasonal variations.
2.5 Sex Identification
Carica papaya is a polygamous diploid plant species with three basic sex types: male,
female and hermaphrodite. Studies have been conducted for identifying the sex of
papaya plant before flowering but till date no definite criteria have been found. Papaya
seeds of deep brown colour produced a higher proportion of female plants than light
coloured seeds. However, it was not clear whether this was due to relationship between
seed colour and sex or due to relationship between age of seed at the time of picking,
as indicated by colour and sex. He further observed that female seedlings at 12 weeks
had higher stem elongation than male seedlings. Male plant had longer internodes and
the female had greater stem girth in the flowering zone than male before flowering.
Weaker seedlings had greater chances of being pistillate than strong ones. Staminate
plants had noticeable lower mean height at first flower buds than the pistillate plants.
Dark seeds of papaya were associated with high proportion of female and male plants,
dark brown seeds of medium size were conducive to female flowers, whereas dark
brown seeds of large size produced predominantly male plants. Identification of
molecular and morphological markers like leaf markers and rate of growth at the juve-
nile and seedling stage for different sex types and their evaluation at flowering stage
in five varieties of papaya namely, Ratna, Washington, Honeydew, CO-6 and CO-2,
it was found that based on the leaf morphology and rate of growth, male and female
seedlings could be identified at seedling stage. The study indicated that the seed-
lings start with single-lobed leaves and differentiate into three- and five-lobed leaves.
Three-lobed leaves are predominant in males and five-lobed leaves in females. Leaf
morphology and rate of growth at seedling stage have been exploited in identifying
the presumptive male and female seedlings at the juvenile seedling stage (60–75 cm
height). This is the first report of the identification of sex types at seedling stage and
has great impact on economic returns to farmers and horticulturists. The earlier given
results were confirmed through RAPD (Randomly Amplified Polymorphic DNA) for
different sex types and at flowering stage in field (Reddy et al. 2012).
Chemical analysis to identify the sexes at seedling stage showed that when semen
reagent (mercury dissolved in red fumic nitric acid and diluted) was added to alka-
line water extract of dried leaves to which a saturated CuSO 4 solution was added,
the resulting colour distinguished mature male and female plants. The same test on
leaves of undifferentiated seedlings predicted sex correctly in 67% and 87% of male
and female seedlings, respectively. Different protein patterns were observed in leaf