The Plus Tree Selection And Tissue Culture Of Nitraria Tangutorum Bobr.

Nitraria tangutorum Bobr. is an advanced species in Nitraria genus. Not only its drupes h ave h igher economic v alue, b ut also t he ' nitre s and piles' which be formed by many N. tangutorum clones, play an important role on local environment protection. With the help of studies on genetic improvement, cultivars of N. tangutorum aimed at its fruit-use and ecological efficiency can be selected. Breeding the new cultivars which with higher yield, delicious taste, small core and nice appearance is the key factor to exploit N. tangutorum resource and is also a most important factor to promote the local economic development and protect local ecological environment. In the research, the fruiting characters variations and plus tree selection have been engaged. Studies on callus culture of N. tangutorum was also involved in the paper. The main results went as follows:1. The variations of N. tangutorum fruit traits were significant among the candidate trees. The variations of drupe traits were noted among clones, while there was little difference in individual. For example, the drupe diameter and weight of B17, the best one, were 24.3%, 76% more than the average of the candidate trees, and just 90.7%, 591.9% higher than those of the control, respectively. N. tangutorum clones also varies in core weight. RCD (ratio of core to drupe) had significantly negative correlation with drupe size and drupe weight in different clones. Selection based on drupe size could meet requirement of PS (percentage of sarcocarp). At the same time, the fruiting-cyme weight, which determined yield was different among clones. B19, the best one, was 126.4% more than the average of candidate trees and 686% higher than that of the control. Regard to individual, not all of the fruit traits is superior, so selection by multi-characters is needed.2. According to drupe size and taste, 39 candidate trees were selected. Their average drupe diameter, length and weight were 53.46%, 49.16%, 288.5% more than that of control respectively. On the base of the principal components and their contributions, 20 plus trees were selected from 39 candidate trees. Their fruiting-cyme, weight, drupe weight, drupe length, drupe diameter, percentage of sarcocarp were higher 23.17%, 6.17%, 18.55%, 3.02%, 7.96%, 1.59%, than those of candidate group respectively.3. The process of N. tangutorum callusing initially occurred from vascular bundle of the part of wound or axillary bud. No difference existed between morphology apical and basal segments of explant. Based on callusing rate, the process of N. tangutorum callusing could divided into promotion stage, callusing stage, stability stage. A new concept, Callusing Vigor which r epresent both of callusing speed and ability had been offered. With index such as Callusing Vigor, analysis of effects of different treatments had been carried on. The data indicate that type of explant is the most important factor on callus induction of TV. tangutorum, blade are worse than stem in inducing callus. Other factors such as cytokinin and organic addition have little effect on callus induction. Callusing vigor was the mostsensitive index for evaluation of callus induction. To be confirmed by callusing vigor, using stem as explant, cultured on MS medium containing 2,4-D 1.0mg/L, sugar 30g/L, agar 4g/L, was the optimum treatment combination of N. tangutorum callus induction. The planet regeneration from N. tangutorum callus is difficult. It needs further research.