Cryopreservation of Ginseng Pollen

Cryopreservation of pollen from two ginseng species —Panax ginseng L. and P. quinquefolium L.—was studied. Freezing anthers that served as pollen carriers to –40C before liquid N storage affected pollen viability little after liquid N storage. Anther moisture content affected pollen viability significantly when stored in liquid N. The ideal anther moisture content to carry pollen for liquid N storage was 32% to 26% for P. ginseng and 27% to 17% for P. quinquefolium. Viability of pollen from P. quinquefolium anthers with 25.3% moisture content changed little after 11 months of liquid N storage. Maintaining pollen viability and fertility for along period is important in plant breeding and conserving plant germplasm resources. Studies have shown that cryopreservation of pollen in liquid N (–196C) is art ideal strategy for long-term preservation (Towill, 1985). We report a study of pollen viability and fertility in two ginseng species —Panax ginseng and P. quinquefolium —after liquid N storage. Fiveyear-old plants of both species were used. Anthers served as the pollen carriers because ginseng pollen is too small to handle individually. Unopened mature anthers were collected. Some of them were wrapped with paper, placed in 1.2-m-diameterplastic test tubes, and sealed with stoppers. The tubes with anthers were immersed in liquid N, either directly or after prefreezing. Prefreezing was stepwise: temperature was lowered from 0 to 10C at 1C/min and kept at –10C for 15 min, then cooled to –40C at the same freezing rate, and kept at –40C for 2 h. Other anthers were placed in culture dishes and dried to various moisture contents with a forced-air fan. A sample of the fan-dried anthers was weighed and moisture content was determined. The rest of the anthers was stored in liquid N. Anther moisture content was determined from anther fresh weight and constant dry weight, which was obtained by drying anthers at 105C for 45 min. After their removal from liquid N, anthers were thawed in a 39 to 40C water bath (fast thawing). Pollen viability was estimated using the following three methods. 1) Staining. Anthers were cut open after being thawed and stained with 0% to 1% fuchsin basic for 10 min (Xue, 1985). They were rinsed with water three times and examined under a microscope. A pale-red color Received for publication 30 Mar. 1992. Accepted for publication 12 Jan. 1993. Supported by National Natural Scientific Foundation of China. We thank Paul H. Li, Laboratory of Plant Hardiness, Dept. of Horticultural Sciences, Univ. of Minnesota, St. Paul, for his assistance. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. 1Former Visiting Scholar at the Laboratory of Plant