Abstract
Roses are one of the most highly produced and purchased ornamental plants worldwide. Procurement and preservation of pollen is essential for the production of diverse rose varieties. In this study, we analyzed pollen management conditions, such as the pollen collection stage, drying time, and storage temperature, to determine optimal conditions for rose pollen management. Pollens were stored under different conditions and the pollen vitality and germination rate were investigated through an optical microscope. The vitality of pollen was an essential factor for rose breeding and depended on the storage conditions. Collecting pollen in the seventh flowering stage resulted in a relatively higher pollen yield. Drying the flower for 5 h after the anther opened improved pollen germination. The germination rate of freshly collected pollen was similar to that of pollen stored at temperatures between −20 °C and −72 °C for up to 30 days, indicating the efficacy of pollen storage at sub-zero temperatures. Since the rate of fruiting increases when pollination is performed three times, considering the time and cost of breeding, it is appropriate to pollinate three times to increase the number of seeds. This study provides an efficient pollen management method to collect and store pollen for breeding.
Conclusions
This study was conducted to develop a method for managing rose pollen that can increase breeding efficiency. For the management method, pollen vitality was analyzed through the treatment of the anther collection, considering the flowering step, pollen drying time, and pollen storage temperature. The effect of the storage method was explained by analyzing the fruit rate through a crossbreeding experiment with pollen according to the specified storage conditions. The normal pollen rate and pollen germination rate of the pollen obtained in flowering stages 3, 5, and 7 were not significantly different. However, since the amount of pollen was the highest at the seventh stage, it is advantageous to collect anthers at the seventh stage of flowering to obtain a lot of pollen. The optimal pollen drying time for pollen germination was five hours after the anther was opened, and as the drying time increased, the pollen vitality significantly decreased. When dried pollen was stored at low temperatures of −20 °C and −72 °C for 30 days, the germination rate of the pollen was similar to or slightly lower than immediately after pollen collection. However, the germination rate of pollen stored at an ordinary temperature (26 °C) was very low. It is effective to store pollen below 0 °C. The pollen collected at the third stage of flowering was dried for 5 h and then stored at −20 °C for 30 days before hybridization. The percentage of normal pollen in the two varieties of male parents used in breeding was about 18%, but the vitality of normal pollen was high. As the number of pollinations increased, the fruit set percentage tended to increase, and there was no significant difference between the third and fifth times. Considering the economic aspects of time and cost of breeding, the appropriate number of pollinations to increase the number of seeds is three.
This study suggested a method for efficiently collecting and utilizing pollen from a specific type of genetic source. The results of this study may be helpful in breeding roses that reflect consumption trends by collecting pollen from various individuals to increase the fruiting rate of crossbreeding. To increase the fruiting rate after pollination, it is important not only to manage the pollen of the male parents but also the form of the hypanthium used as the female parents. A follow-up study is required on the form of hypanthium and the crossability of the female parents that produce good results.
I hope that science and research do not take up too much space at the moment. However, considering the rose breeding season still to come or already underway, this topic could be quite relevant for some of us.
