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

Abstract

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 Akaike's 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.