Pollen Grain Preservation at Low Temperatures in Valuable Commercial Rose Cultivars

Abstract

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.

Pollen Grain Preservation and Fertility in Valuable Commercial Rose Cultivars

“…According to our previous observations, the viable level of fresh rose pollen is cultivar dependent and related to the temperature of conservation [ 6 ]. At room temperature rose pollen germination quickly decreases.…”

“…Anthers were air dried for 24 h at room temperature (T = 24 °C 50% humidity) to favour release and drying of the pollen, then they were weighted in aliquots, of 100 mg and stored in polyethylene tubes at T = −20 °C in the freezer and at T = −80 °C in the deep freezer ( Figure 1 ). The percentage of pollen germination (mean ± standard error) was evaluated on artificial culture medium [ 4 ] after 24 h at 24 °C, (Day 0), in dark conditions, and after a cold storage period of 44, 134 and 190 days, respectively [ 6 ]. In a preliminary test we have observed that pollen germination of control was reduced to zero after 10 days at 24 °C (data not shown).…”

“…Rose breeding companies may overcome geographic distances and differences in flowering time by storing selected pollen until pollination of the flowers used as female parents can be performed. Pollen viability is genotype dependent and affected by the way of storage [ 2 , 3 , 4 , 5 , 6 , 7 ]. In fact, pollen longevity quickly decreases when maintained at ambient temperature and 50% humidity [ 8 , 9 ].…”

Characterization of cultivars and low-temperature pollen grain storage in amaryllis (Hippeastrum sp.)

“…The pollen grain storage is of special interest when natural flowering of the parents is difficult. In floriculture, this is especially interesting for the following reasons: the production of new cultivars is based on the use of hybridization techniques, with crosses between elite genotypes, followed by progenies evaluation and selection (Cardoso et al, 2016;Cardoso, 2017) and crosses between species with different flowering periods may result in F1 hybrids with natural flower production in more than one season per year, or even outside the flowering period of their parents (Gomes et al, 2003;Giovannini et al, 2015).…”

“…Other simplified methods also use low-temperatures for preservation of pollen grains, but are applied for short periods of storage (days, weeks, months) including freezer storage (-10 to -20 °C) and refrigerator (5-10 ºC), already reported in Citrus species (Ali & Perveen, 2014), castor (Vargas et al, 2009), olives (Zambon et al, 2018), roses (Giovannini et al, 2015) and kiwi (Borghezan et al, 2011).…”