Effect of temperature on pollen germination for several Rosaceae species: influence of freezing conservation time on germination patterns

Abstract

[EN] Between February 2018 and April 2018, flowers were collected from eight Rosaceae species. Flowers were kept in a freezer at -20 degrees C for three freezing times (Treatment 1, two months; Treatment 2, four months; Treatment 3, six months). After extracting pollen, in vitro germination was induced in a culture medium and incubated at six different temperatures for 72 h. The percentage of pollen germination, average pollen tube length and maximum pollen tube length were measured. Pollen germination was maximum for all species between 15 degrees C and 30 degrees C. Cydonia oblonga, Malus sylvestris, Prunus avium, Prunus domestica, Prunus dulcis, Prunus persica and Pyrus communis obtained 30-52% pollen germination between 15 degrees C and 20 degrees C. Prunus cerasifera had 40% pollen germination at 30 degrees C. All species studied reached the maximum pollen tube length between 10 degrees C and 25 degrees C. Germination did not change significantly for any of the species with freezing time, but we found significant differences in the three parameters measured between treatments. The highest germination percentages were obtained in Treatment 2 (four months frozen at -20 degrees C), while the maximum pollen tube length was reached in Treatment 1 (two months frozen at -20 degrees C). According to our results, freezing time affected the germination-temperature patterns. This could indicate that studies on the effect of temperature on pollen germination should always be carried out with fresh pollen to obtain more conclusive data.