Studies On The Identification Of The Property Of Natural Loss Of Astringency And Cryopreservation Of Non-astringent Persimmons Germplasm Originated In China

Non-astringent persimmons originated in China are precious resources, which were produced during the long-term cultivation under the effect of genetic variation and selection naturally or artificially. However, at present, those resources have not been used effectively, which shows in two sides: firstly, the property of natural loss of astringency has not been identified by the numbers as so far. Secondly, the procedure for cryopreservation of dormant shoot tips from non-astringent persimmons originated in China needs optimizing furthermore.In order to make full use of our invaluable non-astringent persimmoms germplasm and create new better cultivars or types with the virtues of big fruits, few seeds and fine quality, non-astringent persimmons originated in China were used as materials to identify the property of natural loss of astringency and cryopreserve dormant shoot tips, and the major results as follows:1. By the observation of the tannin cells in fruits flesh and the determination of the soluble tannin content, we found that, area of per tannin cell became smaller, the proportion of tannin cells in per unit area flesh was lower also, and the content of soluble tannin was under 0.2%. Therefore, a conclusion was made down by us: as the property of natural loss of astringency was concerned, 'Luotiantianshi', 'Qiuyantianshi', 'Xiangxitianshi', 'Baogaitianshi', 'Huashi N0.1' all belong to pollination constant non-astringent persimmons.2. In this research, effect of sucrose content, loading time, and the time expose to PVS2 on the survival rate of the shoot tips after cryopreserved, and an approach for cryopreservation of dormant shoot tips was entablished by encapsulation-vitrification method, namely, excised shoot tips about 1 mm in length, were encapsulated into alginated-gel beads. Then alginated-coated shoot tips were precultured on a modified MS basal medium supplemented with increasing sucrose containing of 0.3, 0.5, 0.7, 1.0 mol/L for 1 day. After preculture, encapsulated shoot tips were loaded with a mixture of 2 mol/L glycerol plus 0.4 mol/L sucrose for 20 min. Following loading, encapsulated shoot tipswere dehydrated with a highly concentrated vitrification solution (PVS2 ) for 2 hat 25 癈, and then plunged directly into liquid nitrogen. After rapid warming in water for about 1-2 min at 40 , the shoot tips were rinsed with the modified MS (Murashige and Skoog, 1962) medium containing 1.2 mol/L sucrose for 20 min, and then cultured on the modified medium with 2.2 mg/L ZT and 600 mg/L PVP in dark prior to exposure to the light. The best survival rate of encapsulation vitrified shoot tips amounted to nearly 100% and no abnormality was observed.