Tu Lili

Studies of new EST-SSRs derived from Gossypium barbadense

Existing cotton EST-SSR markers are mostly derived from Gossypium arboreum and Gossypium hirsutum, but EST-SSR markers from Gossypium barbadense are scarce. One hundred and nineteen EST-SSRs were developed based on 98 unique ESTs from a cDNA library constructed in our laboratory using developing fibers from G. barbadense cv. Pima3–79. Among the SSRs, trinucleotide AAG appeared at a high frequency of 11.76%. 36 accessions (consisting of 13 diploids of the A genome, 11 diploids of the D genome and 12 allotetraploids of the AD genome) were employed to test new EST-SSRs. 76 EST-SSRs were successfully amplified, and 313 polymorphic fragments were yielded, with an average of 4.11 fragments per primer pair. The PIC ranged from 0.17 to 0.95 with an average of 0.53. Based on Jaccard’s genetic similarity coefficient, these 36 accessions were clustered into three groups. 21 EST-SSRs exhibited polymorphisms in BC1 population ((Emian22 × Pima3–79) × Emian22), 24 polymorphic loci were generated, while 22 of the 24 polymorphic loci were integrated with our interspecific BC1 backbone genetic linkage map, and anchored in 12 chromosomes. This study effectively proved that EST-SSRs from G. barbadense are valuable for genetic diversity analysis and genetic mapping.

Flavonoid Pathway in Cotton Fiber Development

Cotton fiber is the most important natural fiber. Development of colorful cotton varieties with super quality has always been an important goal of cotton genetics and breeding research. Flavonoids that are associated with the formation of pigment are important plant secondary metabolites. In this review, we describe the advances of flavonoid pathway in cotton fiber: brown pigments in cotton fiber may mainly belong to proanthocyanidins. The flavonoid pathway is down-regulated in white cotton with domestication process, but in white cotton, gene expression profiling data show that genes involved in flavonoid pathway are still very active in fiber development. It was generally believed that flavonoids negatively correlated with fiber quality, naringenin and dihydrokaempferol may inhibit the development of fiber. Flavonoid metabolism and lignin metabolism have common metabolic precursors and genes involved in lignin metabolism are also very active in fiber development, and effective regulation of the metabolism of flavonoids, meanwhile coordinating lignin metabolism, may contribute to fiber development.