Studies On Conservation Of Shoot Tips Of Strawberry In Vitro

Strawberry is an important economic and nutritious fruit crop throughout the world. Traditionally, genetic resource conservation for Strawberry is usually maintained as plants in fields. In these gene banks, the plants are need for periodic replanting and subject to risks of losses caused by biological and natural hazards such as bad weather, pests and diseases. Field maintenance for strawberry is space-demanding and very costly. Thus there is a necessity of creating duplicate collection as a base collection for long-term preservation.This paper explored the germplasm resources' preservation in vitro of the strawberry. The study included the factors which were temperature, sealing material, light intensity, retardant, nutrition, which affected the quality of the preservation in vitro of strawberry. Cryopreservation of in vitro culture shoot tips of strawberry was also been explored. The main results were as follows:1. Preservation in vitro of strawberry shoot tips at different conditionAluminium foil as sealing material was favour of the preservation in vitro of strawberry shoot tips. Weak light was not good for the growth and preservation in vitro of the plantlet under normal temperature. The activated carbon in medium could inhibit the bud shooting and absorb some harmful substance the root secreted. Low temperature was favour of the preservation in vitro of the strawberry shoot tips. The bud shooting and growing were inhibited at 6℃, and the survival rate of the buds was 100% after preserving for 13 months.2. The effects of the retardants on the preservation in vitro of strawberry shoot tipsThe PP333 could inhibit the growth of the plantlet. The plantlet treated with PP333 could be kept more 2 months than control. ABA could delay the bud shooting and growing and inhibit the root. The subculture time was extended to 20 months with 3.0mg/L~6.0mg/L ABA in the medium. The plantlet of the strawberry could be preserved for 15 months with 2% mannitol in the medium at low temperature. So ABA was the best retardant.3. The effects of the nutrition on the preservation in vitro of strawberry shoot tipsMineral nutrition with low concentration, sucrose and agar with high concentration could inhibit the plantlet growing in vitro. The medium which was1/4MS, 0.5mg/L 6-BA,15g/LSucrose and 12.5g/LAgar was tested best. The plantlet invitro could be preserved more than 11 months under this medium at regulartemperature.4. Preliminary study of cryopreservation of strawberry shoot tipsThe shoot tips of in vitro cultured strawberry were successfully cryopreserved. Excised shoot tips were precultured for 12 days on solid MS medium with 2% dimethylsulfoxide. They were first treated with a less toxic solution which contains 20% glycerol and 0.4M sucrose (pH 6.0) at room temperature for 20 min, and pretreated in PVS which contains 35% glycerol and 20% ethylene glycol in the liquid MS medium containing 0.6M sucrose (pH6.0) at 4℃ for 50 min before being immersed in liquid nitrogen. After 1 min warming at 40 ℃, shoot tips were rinsed with liquid MS medium containing 1.2M sucrose for 30 min and transferred onto MS medium supplemented with BA 0.4mg/L, NAA 0.05mg/L and GA 0.15 mg/L. The most survival and regeneration rate of shoot tips reached 82.4% and 100% respectively. This is the first report on the cryopreservation of strawberry by one step vitrification procedure.