Location: Southern Horticultural Research
Title: Pollen viability and storage temperature for Southern highbush and Rabbiteye blueberry breeding Authors
Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: July 9, 2013
Publication Date: N/A
Interpretive Summary: Blueberry plants are becoming more popular as dual purpose ornamentals. Significant correlation has been reported between pollen viability and fruit quality parameters in blueberry. Additionally, low blueberry pollen viability has been linked to poor fruit set. Therefore, maintaining viability of stored pollen for a determined amount of time can be crucial to crop improvement programs, particularly when the genotypes to be hybridized have asynchronous flowering or are geographically separated. Germination percentage of pollen tetrads from four rabbiteye and four southern highbush blueberry genotypes immediately after collection (fresh) and after 2, 4, 6, or 8 weeks of storage at room temperature (22 ºC), in a refrigerator (4 ºC), or in a freezer (-20 ºC) was determined. Germination percentage of fresh blueberry pollen was generally high, but storing blueberry pollen tetrads at room temperature or in a freezer resulted in rapid decline in germination ability. From our results, it can be concluded that germination of rabbiteye and southern highbush blueberry pollen is best maintained when pollen is refrigerated at 4 ºC.
Technical Abstract: Pollen viability, as measured by tetrad germination, has been reported, but these studies focused on freshly collected pollen and did not address viability of pollen stored at different temperatures over time. Moreover, genetic differences in pollen viability have been reported in blueberry genotypes, so knowledge of pollen viability in genotypes at hand for hybridization is desired. Therefore, the objective of this study was to determine appropriate temperature parameters for storage of blueberry pollen, focusing on four rabbiteye (DeSoto, MS1228, MS282, MS454) and four southern highbush (Biloxi, Gupton, MS1377, Rebel) blueberry genotypes. Fresh pollen was collected from field-grown plants of these four genotypes. Germination percentage was determined for fresh pollen and pollen grains stored at 22 ºC, 4 ºC, or -20 ºC after 2, 4, 6, or 8 weeks. An in vitro pollen germination test was performed to evaluate pollen viability using the "hanging drop" technique. Germination percentage of fresh pollen was high in all genotypes tested, ranging from 67% to 87% in rabbiteye and 89% to 95% in southern highbush blueberries. Germination percentages of all genotypes under all storage temperatures declined over time. This decline was particularly pronounced when pollen grains were stored at room temperature (22 ºC) or in a freezer (-20 °C). Germination capability over time was best maintained when pollen was refrigerated at 4°C. In general, pollen grains from rabbiteye genotypes appear to better maintain germination capability over time. For example, germination percentages for rabbiteye pollens stored at 4°C ranged from 36% (MS1228) to 84% (MS454) after 4 weeks, whereas those for southern highbush genotypes ranged from 0% (MS1377) to 9% (Gupton and Rebel) for the same storage duration. In conclusion, pollens of most genotypes remained viable for at least 4 weeks and germination of blueberry pollen was best preserved in refrigeration (4°C).