Optimum sucrose concentration for testing the pollen germination of apple cultivars

The germination of pollen is a key factor in the fertilization success of self-incompatible flowering trees such as apple (Malus domestica Borkh.). Breeding programs have a particular interest in evaluating the germinability of pollens from the male parents before performing controlled crosses. In vitro pollen germination is often considered a simple reliable method to determine the exact amount of viable pollen but the composition of the artificial medium has important implications. In this study, we evaluated the optimal concentration of sucrose (5, 10, 15 and 20%) in the agar-plate medium by testing the germination capacity of 8 apple cultivars. Over the concentrations tested, 15% sucrose solution gave the best results followed by 20%. The percentage of germination significantly varied among cultivars. In the 15% sucrose concentration, the highest percentage was found in ‘Perurico’ (95%) and the lowest in ‘Raxina Dulce’ (66%). These levels are sufficient for an effective fertilisation. Furthermore, the germination of pollen was not affected by the flowering date of the cultivars.