Genetic Analysis of Major Gene and Polygene Inheritance of Chlorophyll Content in Chieh-qua Pulp

【Objective】A major gene and polygenes genetic analysis on the chlorophyll content in the pulp of cheih-qua was conducted to study the relationship and genetic mechanism between pulp color and chlorophyll content, with an aim to lay a foundation for the breeding of high-quality cheih-qua varieties.【Method】In the study, cheih-qua inbred lines J16 (white pulp) and FJ5 (green pulp) were used to form four generation populations, P1, P2, F1 and F2. The pulp color of the chieh-qua was observed by naked eye and the chlorophyll content was measured. The genetic model analysis software package was used to analyze the chlorophyll content of the pulp, and the maximum likelihood function value and AIC value were obtained. Then, the three models with the smallest AIC values were selected as alternate models and the suitability test was carried out. Finally, the first- and second-order genetic parameters of the optimal genetic model were calculated, and the genetic effect values of major genes and polygenes were analyzed.【Result】The results showed that chlorophyll content was the key factor in the formation of green pulp of the chieh-qua. The color and chlorophyll content of the F1 generation were between the parents and slightly inclined to the white pulp parents (P1), and the color and chlorophyll content of the F2 generation showed quantitative characteristics. The optimal genetic model for chlorophyll content in the pulp was MX2-ADI-ADI, that is, 2 pairs of additive - dominant - epistatic major gene + additive - dominant - epistatic polygene models. In the first-order genetic parameters, the sum of absolute additive effects (da+db) of the two major genes was greater than the sum of absolute dominant effects (ha+hb), and da > db, indicated that the negative additive effect of the first major gene was dominant. In epistatic genetic effects, gene additive-additive interactions were the main positive effects. The second-order genetic parameters indicated that the genetic variance of the major gene was 32.1590, the genetic variance of the polygenes was 1.1540, and the heritability rates of the major gene and the polygenes were 93.69% and 3.36%, respectively.【Conclusion】The heritability of major genes for the pulp color of chieh-qua is much higher than that of polygenes, and the major genes are dominant. Therefore, we should pay attention to the use of major genes in the process of high-quality breeding of chieh-qua, and we can select in early generations and improve chieh-qua by combined breeding.