Huang MinRen

Trilocus Disequilibrium Analysis of Multiallelic Markers in Outcrossing Populations

Multiallelic markers, such as microsatellites, provide a powerful tool for studying the genetic structure and organization of an outcrossing population. However, statistical methods of analyzing multiallelic markers in current literature are limited in scope due to the complexity of the multiple alleles. We present a closed-form EM algorithm framework to estimate trigenic linkage disequilibria coefficients of three multiallelic markers and present joint and separate statistical hypothesis tests of different linkage disequilibria. Linkage disequilibria analysis with three multiallelic markers is shown to be considerably more powerful than a two marker analysis or a three marker analysis that treats the multiallelic markers as biallelic markers. A three multiallelic marker model was used to analyze marker data from Lycoris longituba, a tulip-like ornamental plant in China, where each marker consisted of two to four distinct alleles. This algorithm will be useful for studying the pattern of genetic variation for outcrossing populations.Multiallelic markers, such as microsatellites, provide a powerful tool for studying the genetic structure and organization of an outcrossing population. However, statistical methods of analyzing multiallelic markers in current literature are limited in scope due to the complexity of the multiple alleles. We present a closed-form EM algorithm framework to estimate trigenic linkage disequilibria coefficients of three multiallelic markers and present joint and separate statistical hypothesis tests of different linkage disequilibria. Linkage disequilibria analysis with three multiallelic markers is shown to be considerably more powerful than a two marker analysis or a three marker analysis that treats the multiallelic markers as biallelic markers. A three multiallelic marker model was used to analyze marker data from Lycoris longituba, a tulip-like ornamental plant in China, where each marker consisted of two to four distinct alleles. This algorithm will be useful for studying the pattern of genetic variation for outcrossing populations.

A preliminary analysis of phylogenetic relationships ofArundinaria and related genera based on nucleotide sequences of nrDNA (ITS region) and cpDNA (trnL-F intergenic spacer)

Phylogenetic relationships ofArundinaria and related genera (Pleioblastus, Pseudosasa, Oligostachyum, Bashania, Clavinodum, etc.) were assessed by analyzing the sequences of the nrDNA internal transcribed spacer (ITS) and the cpDNAtrnL-F intergenic spacer (IGS). Comparison withtrnL-F IGS sequence, the ITS region provided the higher number of parsimony informative characters, and the interspecific variation of the ITS sequence was higher than that of thetrnL-FIGS sequence. The tree obtained by combining both sets of data showed that the species sampled inArundinaria and the related genera were monophyletic and divided into two clades. The relationships and positioning of all the taxa surveryed (includingA. oleosa, A. hsienchuensis, A. chino, A. amara, A. yixingensis, A. amabilis, A. fortunei, A. pygmaea, A. gramineus, A. fargesii, A. faberi, A. hupehense, Pseudosasa japonica cv. Tsutsumiana, P. japonica andBrachystachyum densiflorum) were also discussed. The results from the sequences were broadly consistent with morphological characters, appearing all these taxa sampled belong to the genus ofArundinaria. The topologies of the trees generated from individual data and the combined data were similar.