Zhao Tuanjie

Association Analysis of Agronomic and Quality Traits with SSR Markers in Glycine max and Glycine soja in China: I. Population Structure and Associated Markers

Association mapping is a procedure for detecting QTLs as well as their alleles based on linkage disequilibrium (LD). The genotyping data of 60 simple-sequence repeat (SSR) markers on representative samples of 393 landraces of Glycine max (L.) Merr. and 196 wild accessions of Glycine soja Sieb. et Zucc. were used in the present study. Linkage disequilibrium of pairwise loci and population structure were firstly analyzed for the two populations, then the association analysis between SSR loci and 16 agronomic and quality traits was performed by using TASSEL GLM (general linear model) program. The different degrees of LD were detected not only among syntenic markers but also among nonsyntenic ones, suggesting that there had been historical recombination among linkage groups. The cultivated soybean population had more LD loci pairs than wild soybean population, while the later had higher degree and slower attenuation of LD than the former. Genetic structure analysis showed that both of the cultivated and wild populations were composed of nine and four subpopulations, respectively, which associated with their geographic eco-types, indicating the classification of geographic eco-types was of sound genetic bases. Twenty seven and thirty four SSR loci associated with the traits were screened out from cultivated and wild populations, respectively. Some loci were found to

Identification, inheritance and QTL mapping of root traits related to tolerance to rhizo-spheric stresses in soybean (G. max (L.) Merr.)

A sample of soybean accessions (Glycine max (L.) Merr.) from Huanghe-Huaihe-Haihe and Middle-Lower Changjiang Valleys in China was used to identify their tolerance to rhizo-spheric stresses, including drought, aluminum toxin and low phosphorus. A total of 15 accessions highly tolerant to at least one of the abiotic stresses were screened out. The correlation between drought tolerance and the relative values of total root length, root volume and dry root weight (relative to dry plant weight) were all significant at 0.01 level, respectively. So did for the correlation between aluminum toxin tolerance and the stress to non-stress ratios of the number of lateral roots, tap root length, total root length, root volume and dry root weight. The inheritance study on the above three root traits related to drought tolerance under segregation analysis indicated that between the two parents of the recombinant inbred line (RIL) population of (Kefeng 1 × Nannong 1138-2), the relative values of dry root weight, total root length and root volume were controlled by two major genes plus polygenes with their major gene heritability values 62.26%–91.81% and polygene heritability values 2.99%–24.75%, respectively, and for the latter two traits, the two major genes linked together with recombination value 4.30% and 1.93%, respectively. The inheritance study on the five root traits related to aluminum toxin tolerance revealed that between the two parents of the recombinant inbred line (RIL) population of (Bogao × NG94-156), the stress to non-stress ratios of lateral root number, tap root length, total root length and dry root weight were controlled by three major genes plus polygenes with their major gene heritability values 80.22%–91.81% and polygene heritability values 3.52%–11.39%, while the stress to non-stress ratio of root volume was controlled by three major genes with their major gene heritability value 93.44%. The (Kefeng 1 × Nannong 1138-2) RIL population was also used for mapping QTLs of relative dry root weight, total root length and root volume related to drought tolerance. Five, three and five QTLs located on Linkage group N6-C2, N8-D1b+W, N11-E and N18-K for each of the three traits, respectively, were identified. Each of the traits appeared to have one locus (Dw1, Rl1, Rv1) with relatively large effect in comparison with their other loci, and the three loci in above parentheses were located in the same region STAS8_3T-STAS8_6T on N6-C2 with a same distance to the flanking markers. Thus, Dw1, Rl1, and Rv1 even might be a same locus and performed as pleiotropic of a same gene. The results between segregation analysis and QTL mapping appeared relatively consistent, therefore could be used for verification each other.

Establishment of Segregation Analysis of Mixed Inheritance Model with Four Major Genes plus Polygenes in Recombinant Inbred Lines Population

The segregation analysis of major genes plus polygenes is a statistical method for genetic analysis of quantitative traits. This method is particularly valuable for breeders to use their data accumulated from segregation populations to estimate the ge- netic system of target traits which is necessary for designing breeding strategies and also useful for validating the results of QTL mapping. The recombinant inbred line (RIL) population is a permanent population, which is suitable for genetic analyses of com- plex traits and can be used in replicated experiments. For RIL, the analytical procedures of three major genes plus polygenes mixed inheritance models have been established and widely used in crops. There is an increasing demand on the genetic model expanding from three major genes plus polygenes to four or more major genes plus polygenes. Therefore, the objective of the present study was to establish the analytical procedures of segregation analyses for four major genes plus polygenes mixed inheri- tance model in RIL population. Fifteen genetic models with four additive and/or epistatic major genes including those without and with polygenes were established. The genetic models and their distribution parameters were solved and estimated with maximum likelihood method and IECM algorithm. The best model was chosen based on Akaikes Information Criterion (AIC) and a set of goodness of fit tests. The genetic parameters of the best model were estimated with the least square method. The established pro- cedure was validated with a set of Monte Carlo simulation experiments. The results showed a relatively high accuracy and consis- tency for first order parameters between the simulated population and scheduled population. For demonstration of the usefulness of the established procedure, the data of palmitic acid content obtained from a RIL population NJRIKY (derived from Kefeng 1 × Nannong 1138-2) along with their P1 and P2 were analyzed. The results showed that the data fitted to Model I-1, i.e. four additive and epistasis major genes plus additive and epistatic polygenes mixed inheritance model.