Genetic parameters of quantitative trait inheritance

The research object of quantitative trait inheritance is population. With the help of mathematical statistics, sampling and statistical analysis are needed to obtain some parameters, so as to clarify the dynamics and characteristics of genetic variation of quantitative traits. There are five main genetic parameters commonly used in quantitative trait inheritance: ① Heritability. That is, the proportion of genetic components in the phenotypic variance (or phenotypic variation) of a trait. ② Combining ability. That is, the measurement of the relative role of two parents (pure line, inbred line or variety) in the yield or other traits of hybrid offspring after hybridization. ③ Genetic correlation. Refers to the correlation between two traits in the same genetic material due to genetic reasons, that is, the correlation between genotype values of this trait. ④ Genetic progress. Also known as genetic gain. That is, under a certain selection intensity, the average value of a certain character of offspring selected from the original population is higher than that of the original population. Expected genetic progress (△G) is a function of selection difference (that is, the difference between the two average values of the previous generation and the next generation after selection) and heritability (h) of traits, that is, △G=ih. I is the absolute value, which is influenced by phenotypic standard deviation (σp). In order to standardize it and compare the selection effects of different characters and different populations, we can divide the two sides of the above formula by σp to get a relative value, which can be written as k and called selection intensity. This genetic progress. If it is generalized heritability,; If there is narrow heritability, then. Measuring genetic progress can estimate the selection effect of a trait. ⑤ Select indicators. Comprehensive selection index. That is to say, the selected target traits are extended to some traits closely related to the main traits, and the following linear relationships are formed according to the relative economic importance of each trait and the phenotypic correlation and genetic correlation between different traits.

Where x 1, x2, x3, …, xn are the phenotypic values of each trait; B 1, b2, b3, …, bn are the weighting coefficients of the corresponding characters; I is the selection index. When selecting, the selection index of the test line or individual plant is calculated, and its value is used as the criterion for staying. In this way, comprehensive selection based on multiple traits is helpful to improve the target traits to the greatest extent.