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Independently Segregating Simple Sequence Repeats (SSR) Alleles in Polyploid Sugarcane

Pan, Yong-Bao, Liu, Pingwu, Que, Youxiong
Sugar tech 2014 pp. 1-8
Saccharum, alleles, capillary electrophoresis, cultivars, flowers, gene segregation, genetic markers, genotype, genotyping, hybrids, microsatellite repeats, nuclear genome, pollen, polyploidy, progeny, sugarcane
The complex nuclear genomic and flower structures of sugarcane cultivars (Saccharum hybrids spp., 2n = 10x = 100–130) render sugarcane a difficult subject for genetics research. Using a capillary electrophoresis and fluorescence-labeling-based simple sequence repeat (SSR) genotyping platform, the segregation of a multiallelic sugarcane SSR marker SMC336BS was investigated among single pollens of a sugarcane cultivar L 99-233 as well as its F1 progenies of a bi-parental cross between HoCP 00-950 (female) and L 99-233 (male). L 99-233 produced five reproducible SSR alleles, namely, 6-154, 6-167, 6-169, 6-171, and 6-175, while HoCP 00-950 produced two SSR alleles, 6-166 and 6-169. Of these six parental alleles, 6-167, 6-169, 6-171, and 6-175 were detected in approximately half of the pollens indicating an independent Mendelian segregation. In addition, four alleles, namely, 6-154, 6-166, 6-167, and 6-175, were detected in approximately half of the F1 progenies, again an indication of independent Mendelian segregation. Twenty-two pollen genotypes were observed among 92 single pollens at frequencies varying from 1.08 to 11.83 % and 33 genotypes were observed among 162 F1 progenies at frequencies varying from 0.62 to 8.64 %. Although none of the 92 single pollens amplified all five parental alleles, one F1 progeny produced all the six parental alleles. Unexpected segregation patterns were also observed. Allele 6-171, which was absent in HoCP 00-950, segregated at 3 presence:1 absence instead of expected 1:1. Allele 6-169, which was detected in both cultivars and segregated at 1:1 among pollens, segregated at nearly 1:0. These unexpected segregation patterns may be associated with the complexity of sugarcane genome and illustrate the needs of additional genetic studies in polyploid sugarcane.