Interrelationships of almond pollen germination at low temperatures, blooming time and biological behaviour of cultivars

A study on the pollen germination of 12 cultivars of almond at low temperatures (5°, 10° and 15°C) and with different times of incubation (2, 6 and 24 hr) is reported. The cultivars showed different responses: the pollen of 'Jordanolo', 'NPU' and 'Peppino Lella' almond was unable to germinate within 2 or 6 hr of incubation at 5°C; the pollen of 'Genco', 'Rachele piccola' and 'Tuono' exhibited germinations in most cases above the mean of the varietal population. A temperature of 5°C induced a satisfactory pollen germination in all cultivars, but only after 24 hr of incubation. The evaluation of pollen germination of the cultivars divided into groups made it possible to ascertain a slower response of early-blooming and selfincompatible groups, due to the lower coefficient of germination rate of the pollen of the same three cultivars, 'Jordanolo', NPU and 'Peppino Lella', present in both groups. The pollen of 'Sannicandro', early-blooming and self-compatible, showed a germination pattern similar to that of the former three cultivars. It is suggested that the genotype of early-blooming cultivars kept the pollen from germinating quickly even at 15°C, a temperature close to the optimum for the species.