| Random amplified polymorphic DNA(RAPD) was used to study the genetic di versity of 100 seedlings from the miniature seeds,1 maternal material and 1 rootst ock.Firstly,the method of DNA extraction was modified for loquat DNA extraction to acquire high quality DNA that was used for RAPD analysis.Secondly,the opt imal RAPD ampification system were established.The primers that were sieved wer e used for sample DNA PCR amplfication.Finally,RAPD fingerprint maps and ex periment data were counted and analysed to acquire molecule characteristic of loqua t samples.The main results of this study were as follows.①The improved CTAB method was the best one for the extraction of loquat g enomic DNA.DNA could be extracted from fresh young leaves and young leaves t hat were preserved by silica gel.DNA extracted by the resultant method of this stu dy had better purity and the output was high.OD260/OD280 of DNA was 1.80-2.05. The DNA integrality was perfect which was detected by electrophoresis in 0.8%ag arose gel.The extracted loquat genomic DNA was qualified for RAPD analysis.②Optimal ampification system of RAPD was established for loquat.In a total volume of 25μL,using the reaction mixtures containing 10×PCR buffer,2.0mmol/L MgCl2,0.2mmol/L of dNTPs,1.2U of Taq Polymerase,0.3μmol/L of RAPD primer, 50ng of template DNA.The PCR reactions were performed in a thermal cycler(P TC-100) programmed for 1 cycle of 4 min at 94℃followed by 45 cycles of 1min at 94℃,1.5 min at 36℃and 2 min at 72℃for denaturing,primer annealing and extension,respectively.The last cycle was followed by incubation for 10 min at 7 2℃.Amplification products were conserved at 4℃and analysed by electrophoresis in 2.0%agarose gel.③9 primers primers which produced the highest number of polymorphic bands and showed consistent and reproducible results were sieved from 120 primers usin g optimal ampification system with three replicates.④The screened 9 primers were applied to the amplification of the specimens. Total 100 bands were produced,in which 83 bands(83.0%) were polymorphic.The average numbers of DNA bands and polymorphic DNA bands amplified by each p rimer were 11.11 and 9.22 respectively.According to the result of amplification,a dendrogram showing genetic relationships was constructed through an unweighted pa ir-group method(UPGMA) and the 102 individuals were clustered into 5 main gro ups.⑤Through the analysis by POPGENE32 1.32,Nei's gene diversity and Shanno n's information index were obtained for the seedlings from the miniature seeds.A rich genetic diversity and abundant mutants were found in the individuals from the miniature seeds,which suggested that the seedlings from the miniature seeds could be very useful for breeding in loquat.⑥Specific bands were found in several individuals from the miniature seeds.N 0.4 s273-250bp,No.34 s22-600bp,No.49 s285-900bp,No.61 s1002-200bp,No.63 s22-250bp,No.75 s1002-600bp,No.88 s22-1400bp have specific bands or lose some bands.These specific molecule mark would be used as the molecular identity tags if the individuals could become cultivars or lines in the future breeding program.
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