| 'Shixia' longan(Dimocarpus longan Lour.) is one of the famous longan cutivars in China .It has great economic value with its delicious flavor .However, the fruit of this cultivar are smaller than those of other longan cultivars which acts as a obstacle for the competition of 'Shixia' longan in national market. In this article, a new cultuvar originated from 'Shixia' longan sport line with bigger fruit and special osmanthus flavor was breeded which will play a important role in the international fruit market.1. The comparison of the fruit characteristics between the 'Shixia' longan sport line and the normal oneThe comparison of the fruit characteristics between the 'Shixia' longan sport line and the normal one was performed in this article .The fruit with sweet osmanthus flavor of the sport line are 26%~31% larger than those of the normal one. Further research also indicated that they are still different in three flavor components.2. Study on genomic DNA extraction from recalcitrant Dimocarpus longan Lour.Two different ways have been developed to extract the high quality DNA from the recalcitrant fruit tree longan (Dimocarpus longan Lour.)which contains abundant polyphenols, polysacchrides, proteins and some other secondary metabolites. The ratios of OD260nm and OD280nm of the genomic DNA extracted by the modified CTAB and SDS methods were respectively 1.82 and 1.73.The comprehensive results from electrophoresis, ratios of OD260nm and OD280nm and RAPD-PCR amplification suggested that the two modified methods especially the modified CTAB can produce high quality genomic DNA while the conventional CTAB and SDS methods are not suitable for the DNA extractionfrom longan.3. Optimization of RAPD conditions of Dimocarpus longan Lour.Based on the high quality genomic DNA extracted by the modified CTAB method, five essential factors that might affect the results of RAPD were compared and the optimun RAPD reaction system for Dimocarpus longan Lour, was established. A 25μl solution with 20ng template DNA, 1U Taq DNA polymerase, 2.0mmol/L MgCl2, each 0.20mmol/L dNTP, 0.20μmol/L random primer would be best for amplification reaction.4. Study on large fruit and sweet osmanthus flavour sport from 'Shixia' longan by RAPD markers160 10-bp single and double random primers were applied to studying the genetic substance difference between the sport branch which could generate larger fruit containing sweet osmanthus flavour and the normal one of the 'Shixia' longan (Dimocarpus Longana Lour.) sport maternal plant by RAPD analysis. 6 single primers and 4 double primers were screened which could produce stable polymorphic segments between the two clones. 13 fragments out of the total 99 amplified ones were distinctive such as S71-560, S161-813, Z70-800, et al, including the loss of a normal segment and appearance of a new one. The difference of amplified DNA segments showed that the genetic substance changed in the sport branch.5. Mechanism of the new fragments amplified by the double primersA single 10-bp random oligonucleotide was often used as the primer in the standard RAPD-PCR analysis. To identify the possibility of RAPD-PCR reaction with double 10-bp primers, 80 double 10-bp oligonucleotides were applied to the RAPD-PCR analysis between the 'Shixia' longan sport line and the normal one. Four double primers, which could produce clear and stability polymorphic DNA fragments, were screened out of the total 80 double primers. Five RAPD makers have been obtained which were linked to the mutation gene of the sport line. Furthermore, the reason that the double primers could produce the new RAPD fragments was also discussed. 6.Inheritance stability of the sport line by way of asexual propagationThe 10 screened polymorphic primers were performed to study the inheritance stability of the sport line originated from asexual propagation. The results indicated that...
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