Analysis of inherited tendency of the main fruit economic characteristics in reciprocal crossing between Senmao 1 and Emerald of blueberry

Abstract:【Objective】In this study, the genetic variation tendency of fruit traits of blueberry hybrids was investigated, and the correlations between different fruit traits were analyzed in order to provide a theoretical reference for scientific selection of parents, reasonable formulation of breeding programs, and improvement of breeding efficiency in blueberry.【Methods】In this experiment, the cross combinations were set as Senmao 1 × Emerald and Emerald × Senmao 1. Senmao 1 is a new northern highbush blueberry cultivar developed by our group, Emerald is a foreign southern highbush blueberry cultivar. The Senmao 1 × Emerald was the positive cross combination producing 156 strains, while Emerald × Senmao 1 was the negative cross combination producing 104 strains. The crossings were made in 2012 and the seedlings were obtained in 2013, and the fruit traits were investigated in 2019 and 2020. Ten ripe fruits were collected randomly from different positions of each plant for examining the fruit traits. The single fruit weight was measured with an electronic balance and the fruit longitudinal diameter, and transverse diameter were measured with a vernier caliper, and then the fruit shape index was calculated. The picking scar, fruit stalk length was measured with a vernier caliper. The fruit firmness was measured with a GY- 4 firmness meter. The soluble solids content, titratable acidity, and solid- acid ratio were determined by ATAGO PAL-BXIACID7. The average values of the measured values of the samples for two consecutive years were used as statistical analysis data, and SPSS 24.0, Excel 2016 were used to calculate the coefficient of variation (CV/% ), heritability (Ta/% ), broad- sense heritability (H2 /%), higher than high parents rate (HH/%), between parents rate (BP/%), lower than low parents rate (LL/%). The SPSS 24.0 was used to produce a range box plot and frequency histogram of fruit traits distribution of hybrids. The R software was used to analyze the correlation and principal component of the main fruit economic traits of Senmao 1 × Emerald.【Results】1) The single fruit weight tended to be lower than the mid-parent value in orthogonal combination and to be similar to or over the mid-parent value in reverse combination. The fruit longitudinal diameter, fruit transverse diameter, and solid-acid ratio showed small genetic variation in the orthogonal progeny and showed medium variation in the backcross progeny. The titratable acidity showed a moderate variation in the orthogonal combination, and a low inheritance in the reverse combinations. The fruit shape index and picking scar showed moderate variation overall and the fruit stalk, fruit firmness length, and soluble solids content showed small genetic tendency in reciprocal cross combinations. 2) The CV of the titratable acidity and the solid-acid ratio was the largest, while the CV range of the fruit longitudinal diameter, transverse diameter fruit, and fruit shape index was the smallest. The H2 of single fruit weight, fruit longitudinal diameter, and fruit transverse diameter was the largest, while the H2 of fruit firmness and titratable acidity was the smallest, which was easily affected by the environmental factors. 3) In the correlation analysis of ten fruit traits of Senmao 1 × Emerald, there were extremely significant or significant correlations among multiple indicators. According to the absolute value of correlation coefficient, the correlation coefficients between the single fruit weight and the fruit transverse diameter (0.849), the titratable acidity and the solid-acid ratio (0.761), the single fruit weight and the fruit longitudinal diameter (0.754), the fruit longitudinal diameter, and the fruit transverse diameter (0.695), the soluble solids content and the solid- acid ratio (0.513) were relatively large. The single fruit weight was significantly and positively correlated with the fruit longitudinal diameter and the fruit transverse diameter, and the three traits were positively correlated with the picking scar and negatively correlated with the titratable acidity. The fruit firmness was positively correlated with the titratable acidity and negatively correlated with the solid-acid ratio. 4) In the principal component analysis of fruit traits of Senmao 1 × Emerald, ten fruit economic traits were trans formed into ten principal components for principal component extraction. The eigenvalues of the first five principal components were 2.909, 1.919, 1.324, 1.128, and 1.011, respectively, which were larger than 1, and the cumulative variance contribution rate was 82.92%, which could reflect the main information of the survey parameters.【Conclusion】Among the ten fruit traits, the single fruit weight, the fruit longitudinal, and the fruit transverse diameter could be stably inherited, while the fruit firmness and the titratable acid seems to be more easily influenced by the non-additive effects and sensitive to environmental effects.