Pollen grain preservation at low temperatures in valuable commercial rose cultivars.

Modern rose cultivars require hand pollination for rose hip production and collection of seeds. Breeding programs are often focused on the quality of rose pollen, which is genotype dependent and it is affected by the conditions used for its conservation. In this study in vitro pollen germination and shelf life of six commercial rose cultivars were evaluated under different storage conditions in order to establish preservation procedures. Flowers of Rosa ‘Alba’, ‘Anastasia’, ‘Encanto’, ‘Marvelle’, ‘Swan’ and ‘Touch of Class’ were collected from plants cultivated in the NIRP International greenhouses. Anthers were removed from flowers and dried on Petri dishes for 24 hours (T= 24°C). Then, they were placed into polyethylene tubes in the freezer (T= -20°C) and in the deep freezer (T= -80°C). Pollen germination was measured soon after 24 hours from flower collection and after 44, 134, and 190 days of storage, respectively. The pollen grains were spread on a culture medium containing agar (0.7%), sucrose (15%), calcium chloride (152 mg L-1) and boric acid (40 mg L-1). Our results confirmed that the viable level in fresh pollen varied among cultivars and also that pollen preservation at low temperatures is cultivar dependent.