草棉EST-SSRs的遗传评价

根据GenBank中公布的247条草棉EST序列，搜索SSR并进行引物设计。其中的25条序列含有27个SSR，1~6碱基重复类型都存在，二碱基和三碱基重复的频率较高。为了明确在A、D和AD基因组中的可转移性，依据25条序列共设计25对EST-SSR引物，其中22对引物扩增出清晰可辨的DNA条带，产生92个多态性片段，平均每对引物产生3.64个多态性片段。引物的多态性信息含量(PIC)在0.49~0.91之间，平均为0.81。6对引物在BC₁种间作图群体(鄂棉22 × Pima3-79) ×鄂棉22]中表现多态性，产生7个多态性位点，其中5个为共显性，2个为显性。除HAU230b标记在BC₁分离群体中不符合孟德尔式分离比例，其余引物表现正常分离。6个位点被整合到陆地棉和海岛棉种间BC₁遗传连锁图谱上的6条染色体：有4个位于A亚基因组的4条染色体上(Chr.6、10、11和12)，2个位于D亚基因组的2条染色体(Chr.19和20)。

Genetic Evaluation of EST-SSRs Derived from Gossypium herbaceum

Gossypium herbaceum (A genome) is generally regarded as the most closely relative of the progenitor at subgenomes of allotetraploid cotton, of which the evolution is necessary to study. In order to investigate the contribution of G. herbaceum to the tetraploid genome, EST-SSRs were isolated from 247 EST sequences of G. herbaceum documented in GenBank. Twenty-seven perfect SSRs were identified from twenty-five unique ESTs. These SSRs contained 1–6 bp nucleotide motifs with high frequency for 2-bp and 3-bp nucleotide motifs. A total of 25 primers were developed and 22 of them could amplify 24 cotton accessions including 7 diploids of A genome, 11 diploids of D genome and 6 allotetraploids of AD genome; only HAU217 could specifically amplified A genome and the other 21 primers could amplified both A and D genomes. The number of polymorphic fragments generated by each primer ranged from 1 to 9 with an average of 3.64. The PIC values ranged from 0.49 to 0.91 with an average of 0.81. Among the 25 EST-SSR primers, six primers revealed polymorphism between Emian 22 and Pima 3-79, and yielded seven polymorphic loci (five were codominant and two dominant) in the BC₁ (Emian22 × Pima3-79) × Emian22] population. Only HAU230b showed distorted segregation in the BC₁ population. Six polymorphic loci were integrated into six chromosomes of our interspecific BC1 backbone genetic linkage map among which, four loci were mapped on four chromosomes of A sub-genome (Chr. 6, 10, 11, 12), and two loci on two chromosomes of D sub-genome (Chr. 19 and 20).