94 Papaya
and seedling emergence. Drying the seeds after conditioning reduced the percent-
age of seedling emergence in the combined treatment involving 400 μM GA 4 + 7 on ly.
Combining matriconditioning with 100 or 200 μM GA 4 + 7 could effectively reduce
germination time and improve seedling emergence, and is recommended as a stan-
dard procedure for testing papaya seed germination (Claudinei and Khan 1993).
8.4.2 Temperature
Papaya thrives best in areas where the maximum temperature does not exceed 40°C
and the minimum does not drop below 10°C. The plants are very susceptible to cold
and frost right from germination till maturity as these not only affect the plant but
also disfigure the fruits due to oozing of latex. Temperature fluctuation or severe
winters from December to February affect the seed production (Figure 8.2). On rip-
ening, the frosted fruit do not have a normal taste and flavour and, thus, remain
unmarketable. In the plains of North India, papaya crop is adversely affected during
summers by the hot winds, thus, frequent irrigation is necessary during this period.
Prolonged droughts associated with high temperatures adversely affect fruit pro-
duction by inducing abortion of floral and fruit structure leading to sterile phases
or skipping of fruiting along the stem. Due to high temperature during summer,
vivipary also affects the seed production. Fruits grown in different states of India,
namely, M.P., Rajasthan, Western U.P., Punjab, Haryana, Delhi, H.P. and Jammu are
affected by either low or high temperature or both. In tropical region round the year,
this crop may be taken economically as compared to subtropical areas due to sever-
ity and duration of winter period.
8.4.3 Sex
The sex forms of papaya present a special problem both to the breeder and to the
grower. The gynodioecious varieties claimed to possess cent percent productive
plants, a wide variation in hermaphrodite population is observed giving from a few
fruits to a number of unmarketable fruits. Under such circumstances, farmers have
to shift to dioecious varieties giving 50% productive plants. By keeping a population
of 5%–10% male plants in a dioecious population, a grower should aim at securing
FIGURE 8.2 (See colour insert.) Deformed and discoloured seeds of papaya.