香蕉EST-SSRs标记的开发与应用

从NCBI搜索的2 282条香蕉EST中, 发掘出含有SSR的EST序列110条, 共有122个SSR位点, 检出率为5.3%。SSR位点可分为37种重复单元, 平均长度为20 bp, 其中二、三核苷酸重复单元的SSR占主导地位, 分别占总SSR的33.1%和47.6%。GA和GAA是二、三核苷酸中的优势重复类型, 分别占二、三核苷酸重复类型的75.7%和36.0%; 其他重复类型所占比例均不足10%, 而四核苷酸重复类型最少, 为4.0%。设计的63对EST-SSRs引物中, 有41对EST-SSRs引物对巴西蕉基因组DNA能扩增出产物, 占总引物数的65.1%。应用进一步筛选出的重复性好、多态性高的19对引物对49个香蕉品种(系)进行PCR扩增。每对引物扩增的多态性带数目为4~12个, 平均7.58个; 引物多态信息量变化范围为0.3572~0.8744, 平均0.7324。在相似系数为0.63的水平可将49个品种聚为2个类群：一类为含B基因组香蕉品种; 另一类为不含B基因组的香蕉品种, 表明EST-SSR引物可以应用于香蕉品种资源分类的研究。

Development and application of EST-derived SSR markers for ba-nanas (Musa nana Lour.)

A total of 2 284 banana unigene sequences were mined, resulting in the identification of 122 SSRs in 110 sequences. Among them, there were 37 motifs the overall average length of SSRs was 20 bp. The trinucleotide repeats appeared to be the most abundant SSRs (47.6%), followed by dinucleotide repeats (33.1%), whereas the tetranucleotide repeats were less abundant. The rich repeats AG and AGG were predominant, accounting for 75.7% and 36% in dri- and tri-nucleotide repeats respectively. A total of 63 primer pairs were designed and tested against genomic DNA of Brazil. Forty-one primers could be validated as usable markers. Nineteen of these primers revealed moderate to high polymorphism information content (PIC) across 49 accessions. The polymorphic bands were ranged from 4 to 12, averagely 7.58. The mean PIC value was 0.7324, ranging from 0.3572 to 0.8744. Forty-nine banana varieties were separated into two major clusters closely corresponding with the genome composition by UPGMA analysis. The results showed that the EST-SSR markers were of great value in evaluation of banana germplasms.