Factors Affecting the Quality and In Vitro Germination Capacity of Strawberry Pollen

ABSTRACT

Poor pollen quality and germination capacity curtails early yield in strawberry. The aim of this study was to establish a reliable method for the in vitro assessment of strawberry pollen germination ability and to investigate further the effects of photoperiod and gibberellin on pollen germination and quality. In the first part of the study pollen from seven strawberry cultivars (‘Chandler’, ‘Selva’, ‘Tudla’, ‘Camarosa’, ‘Eris’, ‘Pajaro’, and ‘Irvine’) was collected and its germination capacity and the incidence of deformed pollen grains was assessed in vitro with the hanging-drop technique. With ‘Selva’ the highest germination rates were observed in a nutrient medium of 10% sucrose, ‘Pajaro’ showing the highest percentage of deformed pollen (76%). In the second part, young strawberry plants, cv. Seascape, were sprayed once with GA3 at 0, 50, or 200 mg 1^-1. Pollen germination and deformation and stamen length were assessed three months later. GA3 at 50 mg 1^-1 increased pollen germination and decreased the incidence of deformed pollen grains, while GA3 at 200 mg 1^-1 decreased pollen germination without affecting the formation of deformed pollen grains. Other plants showed a higher rate of pollen germination under long than under short days. GA3 at 200 mgl^-1 caused a decrease in pollen germination under either short or long day conditions compared to the controls but doubled the percentage of deformed pollen only under short days. Stamens in control plants grew four times longer under long than short day conditions. GA3 did not affect stamen length under long days but enhanced their growth under short days significantly.

Key Words:

• Photoperiod
• gibberellin
• pollen deformation
• sucrose
• calcium nitrate