TOMATO POLLEN STORAGE AT FREEZE AND CRYOGENIC TEMPERATURE - EFFECTS ON VIABILITY AND FECUNDITY

Abstract

Storage at cryogenic temperatures is considered a successful method of retaining pollen viability in many plant species. Storage at ­20°C has also been reported as a convenient method of pollen preservation with satisfactory results. In this study, the effects of two storage methods on tomato pollen viability and fecundity have been compared. Tomato pollen was stored at ­20°C using CaCl2 as desiccant and at ­196°C after modification of its moisture content to 6.5-7% (wet weight basis). After 6, 8, 10, 12 and 18 months, in vitro pollen germination and pollen tube growth were tested following rehydration for 3 h at 100% R.H. and 15°C, and incubation for 6 h on semisolid substrate (1% agar, 12% sucrose and 50 mg L-1 H3BO3). Respiration activity was measured in pollen stored at both ­20 and ­196°C for 6 and 12 months in liquid substrate (12% sucrose and 50 mg L-1 H3BO3). Fecundity of stored pollen was assessed by artificial pollinations conducted at the same time. Pollen stored at ­20°C retained high in vitro germination for 10 months. However, after only 6 months at ­20°C, pollen tube length and respiration activity declined with a negative impact on pollen fecundity, as indicated by the reduced number of seeds per fruit in fruits obtained by artificial pollination. Pollen germination ability significantly declined after 12 months. On the other hand, pollen stored at ­196°C for 18 months exhibited similar in vitro germination, pollen tube growth and respiration activity to those recorded for fresh pollen. Furthermore, artificial pollination with cryogenically stored pollen resulted in similar fruit set and number of seeds per fruit to those observed after artificial pollination with fresh pollen.