Papaya pollen viability and storage

Papaya pollen viability, tube growth and storage were studied. Pollen germination on a drop of modified Brewbaker medium at 22–26°C closely reflected in vivo germination. Two vital stains gave pollen viability estimates that correlated closely with pollen germination percentage. The time from pollination to first ovule penetration was 25 h at 28°C, no in vitro pollen germination was observed at 5°C and at 40°C pollen tube growth was retarded. High relative humidity (70–80%) hastened the process compared with low relative humidity (30–40%).

Pollen could be stored successfully for 6 months when kept at ? 18°C in a deep-freezer. Storage of pollen for the winter months, during which no or very little viable pollen is formed in the coastal area of Israel, seems a practical means to ensure adequate fruit set.