Storage of bahiagrass pollen at different temperatures

Authors: DINATO, N. - Universidade Federal De Sao Carlos; SANTOS, I.R. - Embrapa; LEONARDECZ, E. - Universidade Federal De Sao Carlos; Burson, Byron; QUARIN, C. - Universidad National Del Nordeste; PAULA, A. - Universidade Federal De Sao Carlos; FAVERO, A. - Embrapa

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2018
Publication Date: 8/30/2018
Citation: Dinato, N.B., Santos, I.I., Leonardecz, E., Burson, B.L., Quarin, C.L., Paula, A.F., Favero, A.P. 2018. Storage of bahiagrass pollen at different temperatures. Crop Science. 58:2391-2398. https://doi.org/10.2135/cropsci2018.03.0164.
DOI: https://doi.org/10.2135/cropsci2018.03.0164

Interpretive Summary: When wide hybridization is used to breed improved plants, sometimes plants used as parents do not flower at the same time. When this occurs crosses cannot be made. Flowering time can be changed by adjusting the light and temperature the plants are grown under but this can be difficult. Another way to solve this problem is to collect pollen from the male parent and store the pollen in a cold environment until needed. When a female parent flowers, the pollen is removed from cold storage and used to pollinate the female. We are interested in using this approach on bahiagrass, but its pollen and pollen from its close relatives have never been stored in long-term cold storage. This study was conducted to determine if bahiagrass pollen would remain alive when stored in cold conditions for extended periods of time. Four chemicals were used to dry the pollen before storage and then the pollen was stored in a refrigerator, a freezer, and liquid nitrogen for 10, 60, 120, and 180 days. All samples tested regardless of the drying treatment, storage temperature, or storage time had some live pollen and could be used for pollination purposes. Essentially all of the pollen stored in a refrigerator decreased in quality, even when stored only 10 days. However, some pollen remained as good as fresh pollen when stored in a freezer and in liquid nitrogen. Some pollen that was stored in liquid nitrogen for 180 days kept its quality. This study identified the best protocol for preparing bahiagrass pollen for storage and demonstrated that bahiagrass pollen can be stored for at least 6 months in liquid nitrogen. These findings are important to breeding programs working on the improvement of bahiagrass and other related species.

Technical Abstract: Paspalum is an important genus of grasses that are native to the Americas and some species are important for livestock production in the warmer regions of the world. Efforts to breed improved cultivars require intra- and interspecific hybridization, but asynchronous flowering often occurs between the parental species and prevents hybridization. One method of circumventing this problem is to store pollen using cryopreservation so that viable pollen will be available to pollinate the desired female parent when it flowers. Bahiagrass, P. notatum Flugge, was used as a model to determine if its pollen can be preserved using long-term cold storage. Pollen was dehydrated with lithium chloride (LiCl), magnesium chloride (MgCl2), sodium hydroxide (NaOH), and silica gel for 30, 60, and 120 minutes. Both dehydrated and non-dehydrated pollen were stored at 40C, -200 C, and -1960C for 10, 60, 120, and 180 days. After thawing, pollen stainability and in vivo germination were determined to assess viability. Stainability of untreated fresh pollen was 73.27%, and the treated and stored pollen ranged from 25.33% to 71.33%. Storage at -200C and -1960C was superior to 40C. Statistically, pollen dehydrated with LiCl for 30 minutes stored best at -1960C; whereas, pollen dehydrated for 120 minutes with silica gel and for 30 and 60 minutes with MgCl2 stored best at -200C. All samples, regardless of the treatment, storage temperature, or length of storage, had some viable pollen. These findings demonstrate that bahiagrass pollen can be stored in long-term cold conditions, and this can be used to circumvent the problems associated with asynchronous flowering between parental species used in a wide hybridization program.