92 Papaya
has been fixed for the germination of papaya seed. The freshly extracted seeds
give 90%–100% germination. But as the time passes, the germination percentage
decreases. The stored seed supplied to growers should not have less than 70% ger-
mination in gynodioecious varieties and 60% germination in dioecious varieties
(Ram 1986a). Seed treatments to promote germination and to reduce germination
time have been widely investigated by Salomao and Mundim (2000). Satisfactory
germination percentages were obtained by removing the sarcotesta, exposing dry
seeds at 10°C prior to sowing, soaking seeds in distilled water, potassium nitrate,
thiourea, sodium thiosulfate, tannic acid/ferulic acid and GA 3 , and after that sown
at 20–30°C temperatures.
8.3 Seed Yield
The yield of papaya seed depends upon the cultural practices, sex ratio and pollina-
tion in tropical areas, while seed yield also depends upon the severity and duration
of winter period in subtropical areas. Under normal conditions, the seed yields are
60–75 kg/ha in dioecious varieties. The seed yield is much lower in gynodioecious
varieties because of the poor pollen production in hermaphrodite plants and, there-
fore, the cost of seed production is very high in these varieties. Despite high cost,
farmers prefer the seed of gynodioecious varieties because of saving in raising crops
or roguing of male plants (Ram 1986a).
8.4 Constraints in Seed Production
Papaya is a remunerative but problematic crop and is very much sensitive to agro-
ecological and other factors. Several factors responsible for losses to the farmers and
seed producer in the country are given below.
FIGURE 8.1 (See colour insert.) Traditional method of seed extraction.