Optimization of Pollen Germination Medium and Pollen Collection in Two Japanese Strawberry Cultivars

Strawberries, the most economically well-known berry crop, are known for their taste, nutritional value, and antioxidant compounds. Various spatiotemporal or seasonal factors are known to affect the strawberry pollen germination rate; however, determinating which factor most influences the variation in the pollen germination rate remains challenging. This study aimed to determine the optimal pollen germination media and pollen short-term storage methods in the Japanese strawberry cultivars ‘Shindai SUS-1’ and ‘Shindai BS8-9’. Each strawberry pollen was incubated for 3 h in the dark on a solid medium with 1.5% agar and different sucrose and boric acid concentrations. The pollen germination rate was then investigated. The optimal pollen germination medium for both cultivars was 1.5% agar, 10% sucrose, and 0.1% boric acid. The small amount of strawberry pollen used in this study was collected immediately after flowering in the morning. Therefore, we also investigated a method for collecting a large amount of pollen while maintaining pollen activity. For both cultivars, the pollen germination rate for dry pollen, incubated for 24 h with silica gel after the petals and calyx were removed, was the same as that of the fresh pollen collected immediately after flower collection. In addition, dry pollen was more efficient in terms of short-term storage than fresh pollen. For ‘Shindai BS8-9’, the germination rate for dry pollen was also higher than that of the fresh pollen when stored in vacuum at −25, 4, 15, 20, and 25°C for 3 and 7 days.